Convert equisolidangular to equiangular projection

hdri
1

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

2

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

  pcomb -f fisheye_corr.cal -o fisheye.hdr \
    > getinfo -a "VIEW= -vta -vh 180 -vv 180" \
    > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,
-Greg

···

From: Zhe Kong <[email protected]>
Date: January 25, 2017 1:15:49 PM PST

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.
Zhe

3

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper <http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.

That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

···

On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

  pcomb -f fisheye_corr.cal -o fisheye.hdr \
    > getinfo -a "VIEW= -vta -vh 180 -vv 180" \
    > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,
-Greg

From: Zhe Kong <[email protected]>
Date: January 25, 2017 1:15:49 PM PST

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.
Zhe

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

4

If it is of any interest I did this overview some years back concerning various projections

[cid:[email protected]]

Claus B. Madsen

Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

hemispherical.pdf (740 KB)

···

Phone: +45 9940 8788 | E-mail: [email protected]<mailto:[email protected]>

From: "J. Alstan Jakubiec" <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Thursday, 26 January 2017 at 06.57
To: "[email protected]" <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

  pcomb -f fisheye_corr.cal -o fisheye.hdr \

         > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

         > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,

-Greg

From: Zhe Kong <[email protected]><mailto:[email protected]>

Date: January 25, 2017 1:15:49 PM PST

Dear list:

I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.

1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

_______________________________________________

HDRI mailing list

[email protected]<mailto:[email protected]>

http://www.radiance-online.org/mailman/listinfo/hdri

5

Hello Greg:
Thank you very much for your answer. I will explore more about
fisheye_corr.cal.

Hello Alstan:
Thank you for your explanation. I got this information from the
manufacturer, but based on the paper you sent, I made a mistake. Thank you
for saving my time and effort.

Zhe

···

On Thu, Jan 26, 2017 at 10:11 AM, <[email protected]> wrote:

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Today's Topics:

   1. Convert equisolidangular to equiangular projection (Zhe Kong)
   2. Re: Convert equisolidangular to equiangular projection
      (Gregory J. Ward)
   3. Re: Convert equisolidangular to equiangular projection
      (J. Alstan Jakubiec)
   4. Re: Convert equisolidangular to equiangular projection
      (Claus Br?ndgaard Madsen)

----------------------------------------------------------------------

Message: 1
Date: Wed, 25 Jan 2017 15:15:49 -0600
From: Zhe Kong <[email protected]>
To: [email protected]
Subject: [HDRI] Convert equisolidangular to equiangular projection
Message-ID:
        <CAEV5NycbY6hLjbPSmVb1H5pj_PW-Y4rNMjzrY4KJ2sLXkbV_wA@mail.
gmail.com>
Content-Type: text/plain; charset="utf-8"

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe
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Message: 2
Date: Wed, 25 Jan 2017 16:48:55 -0800
From: "Gregory J. Ward" <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Message-ID: <[email protected]>
Content-Type: text/plain; charset=iso-8859-1

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier
to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
suggested in the fisheye_corr.cal file itself:

        pcomb -f fisheye_corr.cal -o fisheye.hdr \
                > getinfo -a "VIEW= -vta -vh 180 -vv 180" \
                > corrected.hdr

This will also crop the area outside of 180? to black, assuming that is
what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.

Cheers,
-Greg

> From: Zhe Kong <[email protected]>
> Date: January 25, 2017 1:15:49 PM PST
>
> Dear list:
> I am trying to compare HDR images and simulated luminance maps. Since I
use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:
>
> https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html
>
> However, I still have some questions need to figure out.
> 1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?
>
> 2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?
>
> Any suggestions or explanation would be appreciated.
> Zhe
>

------------------------------

Message: 3
Date: Thu, 26 Jan 2017 13:57:36 +0800
From: "J. Alstan Jakubiec" <[email protected]>
To: [email protected]
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Message-ID: <[email protected]>
Content-Type: text/plain; charset="windows-1252"; Format="flowed"

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)
lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am
having trouble finding a source from Sigma right now, but Cauwerts,
Bodart and Deneyer's paper
<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says
so.

That said, if you do end up with an equi-solidangle image, I have a
python script that converts equi-solid angle to equi-angle for each
source jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

On 1/26/2017 8:48 AM, Gregory J. Ward wrote:
> Hi Zhe,
>
> You should be able to apply the fisheye_corr.cal file I gave you earlier
to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
suggested in the fisheye_corr.cal file itself:
>
> pcomb -f fisheye_corr.cal -o fisheye.hdr \
> > getinfo -a "VIEW= -vta -vh 180 -vv 180" \
> > corrected.hdr
>
> This will also crop the area outside of 180? to black, assuming that is
what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.
>
> Cheers,
> -Greg
>
>> From: Zhe Kong <[email protected]>
>> Date: January 25, 2017 1:15:49 PM PST
>>
>> Dear list:
>> I am trying to compare HDR images and simulated luminance maps. Since I
use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:
>>
>> https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html
>>
>> However, I still have some questions need to figure out.
>> 1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?
>>
>> 2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?
>>
>> Any suggestions or explanation would be appreciated.
>> Zhe
>>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri

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Message: 4
Date: Thu, 26 Jan 2017 10:17:01 +0000
From: Claus Br?ndgaard Madsen <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"

If it is of any interest I did this overview some years back concerning
various projections

[cid:[email protected]]

Claus B. Madsen

Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Phone: +45 9940 8788 | E-mail: [email protected]<mailto:[email protected]>

Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

From: "J. Alstan Jakubiec" <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Thursday, 26 January 2017 at 06.57
To: "[email protected]" <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens,
and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having
trouble finding a source from Sigma right now, but Cauwerts, Bodart and
Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.
2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python
script that converts equi-solid angle to equi-angle for each source jpeg
while maintaining the EXIF data. I used this to convert equi-solidangle
images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier
to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
suggested in the fisheye_corr.cal file itself:

  pcomb -f fisheye_corr.cal -o fisheye.hdr \

         > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

         > corrected.hdr

This will also crop the area outside of 180? to black, assuming that is
what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.

Cheers,

-Greg

From: Zhe Kong <[email protected]><mailto:[email protected]>

Date: January 25, 2017 1:15:49 PM PST

Dear list:

I am trying to compare HDR images and simulated luminance maps. Since I
use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html

However, I still have some questions need to figure out.

1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

_______________________________________________

HDRI mailing list

[email protected]<mailto:[email protected]>

http://www.radiance-online.org/mailman/listinfo/hdri

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End of HDRI Digest, Vol 87, Issue 1
***********************************

--
*Zhe Kong*
*PhD Student*
*University of Wisconsin - Milwaukee *
*School of Architecture and Urban Planning *
*2131 E. Hartford Ave, Milwaukee, WI 53211 *
*Office 327*

6

Hi Alstan,

I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?

Cheers
Tobias

···

Von: J. Alstan Jakubiec [mailto:[email protected]]
Gesendet: Donnerstag, 26. Januar 2017 06:58
An: [email protected]
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \

        > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

        > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,

-Greg

From: Zhe Kong <[email protected]><mailto:[email protected]>

Date: January 25, 2017 1:15:49 PM PST

Dear list:

I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.

1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

_______________________________________________

HDRI mailing list

[email protected]<mailto:[email protected]>

http://www.radiance-online.org/mailman/listinfo/hdri

7

Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't measured them for vignetting and angular verification yet. It is on my to do list :). I will be disappointed if they are equi-solid angular however. Will let you know sometime after the Lunar new year.

Alstan

···

On 1/27/2017 6:17 PM, Tobias Porsch wrote:

Hi Alstan,

I'm not sure if your below description is correct.

In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.

Can you please double-check that issue for me?

Cheers

Tobias

*Von:*J. Alstan Jakubiec [mailto:[email protected]]
*Gesendet:* Donnerstag, 26. Januar 2017 06:58
*An:* [email protected]
*Betreff:* Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper <http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.

That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

    Hi Zhe,

    You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

      pcomb -f fisheye_corr.cal -o fisheye.hdr \

             > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

             > corrected.hdr

    This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

    Cheers,

    -Greg

        From: Zhe Kong<[email protected]> <mailto:[email protected]>

        Date: January 25, 2017 1:15:49 PM PST

        Dear list:

        I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

        https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

        However, I still have some questions need to figure out.

        1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

        2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

        Any suggestions or explanation would be appreciated.

        Zhe

    _______________________________________________

    HDRI mailing list

    [email protected] <mailto:[email protected]>

    http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

8

A little followup that is worth noting is that Axel Jacobs measured the Sigma 4.5mm and found it to have an equi-solid angle projection. See his presentation here: https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

···

On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:

Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't measured them for vignetting and angular verification yet. It is on my to do list :). I will be disappointed if they are equi-solid angular however. Will let you know sometime after the Lunar new year.

Alstan

On 1/27/2017 6:17 PM, Tobias Porsch wrote:

Hi Alstan,

I'm not sure if your below description is correct.

In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.

Can you please double-check that issue for me?

Cheers

Tobias

*Von:*J. Alstan Jakubiec [mailto:[email protected]]
*Gesendet:* Donnerstag, 26. Januar 2017 06:58
*An:* [email protected]
*Betreff:* Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper <http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.

That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

    Hi Zhe,

    You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

      pcomb -f fisheye_corr.cal -o fisheye.hdr \

             > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

             > corrected.hdr

    This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

    Cheers,

    -Greg

        From: Zhe Kong<[email protected]> <mailto:[email protected]>

        Date: January 25, 2017 1:15:49 PM PST

        Dear list:

        I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

        https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

        However, I still have some questions need to figure out.

        1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

        2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

        Any suggestions or explanation would be appreciated.

        Zhe

    _______________________________________________

    HDRI mailing list

    [email protected] <mailto:[email protected]>

    http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

9

Hi everyone,

Some years ago I tested my Sigma 8mm lens, f3.5.

At the time I found several sources online claiming it to be equi-solid angle (-vth), but it didn’t match my personal experiences with the lens, so I tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the angular fish eye projection in RADIANCE.

So, in my experience, the 8mm Sigma lens is equidistant.

Cheers,
Claus

Claus B. Madsen

Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

···

Phone: +45 9940 8788 | E-mail: [email protected]<mailto:[email protected]>

From: "J. Alstan Jakubiec" <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Friday, 27 January 2017 at 11.33
To: "[email protected]" <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

A little followup that is worth noting is that Axel Jacobs measured the Sigma 4.5mm and found it to have an equi-solid angle projection. See his presentation here: https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:

Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't measured them for vignetting and angular verification yet. It is on my to do list :). I will be disappointed if they are equi-solid angular however. Will let you know sometime after the Lunar new year.

Alstan

On 1/27/2017 6:17 PM, Tobias Porsch wrote:
Hi Alstan,

I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?

Cheers
Tobias

Von: J. Alstan Jakubiec [mailto:[email protected]]
Gesendet: Donnerstag, 26. Januar 2017 06:58
An: [email protected]<mailto:[email protected]>
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \

        > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

        > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,

-Greg

From: Zhe Kong <[email protected]><mailto:[email protected]>

Date: January 25, 2017 1:15:49 PM PST

Dear list:

I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.

1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

_______________________________________________

HDRI mailing list

[email protected]<mailto:[email protected]>

http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________

HDRI mailing list

[email protected]<mailto:[email protected]>

http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________

HDRI mailing list

[email protected]<mailto:[email protected]>

http://www.radiance-online.org/mailman/listinfo/hdri

10

Hi all,
Thank you for raising this topic and sharing your views. I¹m using the
output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via
Evalglare that should require a -vth or -vta view, so this is critical
information for me.
May I ask why people refer to -vth as equi-solid angle and not hemispherical
as it is defined in Radiance¹s rpict man page?
My understanding from that page and from Axel Jacobs' presentation sent via
the link just before is that there isn't a Radiance description for the
equi-solid angle view.

Best Regards

Raquel Viula

PhD Researcher

TU Delft | Faculty of Architecture and the Built Environment |

Architectural Engineering and Technology

Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA
Delft

···

From: Claus Brøndgaard Madsen <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Friday 27 January 2017 13:49
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi everyone,

Some years ago I tested my Sigma 8mm lens, f3.5.

At the time I found several sources online claiming it to be equi-solid
angle (-vth), but it didn¹t match my personal experiences with the lens, so
I tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the angular
fish eye projection in RADIANCE.

So, in my experience, the 8mm Sigma lens is equidistant.

Cheers,
Claus

Claus B. Madsen
Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Phone: +45 9940 8788 | E-mail: [email protected] <mailto:[email protected]>
Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

From: "J. Alstan Jakubiec" <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Friday, 27 January 2017 at 11.33
To: "[email protected]" <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

A little followup that is worth noting is that Axel Jacobs measured the
Sigma 4.5mm and found it to have an equi-solid angle projection. See his
presentation here:
https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jac
obs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:

Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't
measured them for vignetting and angular verification yet. It is on my to do
list :). I will be disappointed if they are equi-solid angular however. Will
let you know sometime after the Lunar new year.

Alstan

On 1/27/2017 6:17 PM, Tobias Porsch wrote:

Hi Alstan,

I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an
equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant
(-angular) (-vta) lens.
Can you please double-check that issue for me?

Cheers
Tobias

Von: J. Alstan Jakubiec [mailto:[email protected]]
Gesendet: Donnerstag, 26. Januar 2017 06:58
An: [email protected]
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and
the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble
finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's
paper <http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002>
says so.

That said, if you do end up with an equi-solidangle image, I have a python
script that converts equi-solid angle to equi-angle for each source jpeg
while maintaining the EXIF data. I used this to convert equi-solidangle
images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to
correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \
        > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

        > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what
you want. It assumes that you have already cropped the image to a minimum
square area. You should apply vignetting correction and absolute
calibration first.

Cheers,
-Greg

From: Zhe Kong <[email protected]> <mailto:[email protected]>
Date: January 25, 2017 1:15:49 PM PST

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/
011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.
Zhe

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________ HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

11

Raquel points out an important error in this discussion's terminology. The "equidistant" fisheye does indeed correspond to the "-vta" view type in Radiance. However, the "-vth" type corresponds to a hemispherical projection, which very few commercial fisheye lenses realize. In particular, the equisolidangle projection is much closer to "-vta" than it is to "-vth". If your lens is equisolidangle, then you need to use the fisheye_corr.cal script or similar to convert it to an equidistant projection.

I have not implemented the equisolidangle projection, though there is a third fisheye type (-vts) which is called "stereographic", although we prefer the term "planisphere" projection to avoid confusion with stereo views. This does not correspond to any commercial lenses to my knowledge, but I'd be interested to hear of one.

···

From: Raquel Viula <[email protected]>
Date: January 27, 2017 5:49:57 AM PST

Hi all,
Thank you for raising this topic and sharing your views. I’m using the output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via Evalglare that should require a -vth or -vta view, so this is critical information for me.
May I ask why people refer to -vth as equi-solid angle and not hemispherical as it is defined in Radiance’s rpict man page?
My understanding from that page and from Axel Jacobs' presentation sent via the link just before is that there isn't a Radiance description for the equi-solid angle view.

Best Regards

Raquel Viula
PhD Researcher

TU Delft | Faculty of Architecture and the Built Environment |
Architectural Engineering and Technology
Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA Delft

From: Claus Brøndgaard Madsen <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Friday 27 January 2017 13:49
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi everyone,

Some years ago I tested my Sigma 8mm lens, f3.5.

At the time I found several sources online claiming it to be equi-solid angle (-vth), but it didn’t match my personal experiences with the lens, so I tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the angular fish eye projection in RADIANCE.

So, in my experience, the 8mm Sigma lens is equidistant.

Cheers,
Claus

Claus B. Madsen
Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Phone: +45 9940 8788 | E-mail: [email protected]
Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

From: "J. Alstan Jakubiec" <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Friday, 27 January 2017 at 11.33
To: "[email protected]" <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

A little followup that is worth noting is that Axel Jacobs measured the Sigma 4.5mm and found it to have an equi-solid angle projection. See his presentation here: https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:
Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't measured them for vignetting and angular verification yet. It is on my to do list :). I will be disappointed if they are equi-solid angular however. Will let you know sometime after the Lunar new year.

Alstan

On 1/27/2017 6:17 PM, Tobias Porsch wrote:
Hi Alstan,

I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?

Cheers
Tobias

Von: J. Alstan Jakubiec [mailto:[email protected]]
Gesendet: Donnerstag, 26. Januar 2017 06:58
An: [email protected]
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper says so.

That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

On 1/26/2017 8:48 AM, Gregory J. Ward wrote:
Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \
        > getinfo -a "VIEW= -vta -vh 180 -vv 180" \
        > corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,
-Greg

From: Zhe Kong <[email protected]>
Date: January 25, 2017 1:15:49 PM PST

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.
Zhe

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri _______________________________________________
HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

12

Sorry about the confusion I brought up. I got this wrong information from
the manufacturer. If I recall my previous experience, Sigma f/3.5 matches
Radiance -vta pretty well. The current mismatch might be caused by the
camera coordinate in the simulation.
Anyway, Happy Chinese New Year, everyone!

Zhe

···

On Fri, Jan 27, 2017 at 10:11 AM, <[email protected]> wrote:

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Today's Topics:

   1. Re: Convert equisolidangular to equiangular projection
      (Gregory J. Ward)

----------------------------------------------------------------------

Message: 1
Date: Fri, 27 Jan 2017 08:10:53 -0800
From: "Gregory J. Ward" <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Message-ID: <[email protected]>
Content-Type: text/plain; charset="windows-1252"

Raquel points out an important error in this discussion's terminology.
The "equidistant" fisheye does indeed correspond to the "-vta" view type in
Radiance. However, the "-vth" type corresponds to a hemispherical
projection, which very few commercial fisheye lenses realize. In
particular, the equisolidangle projection is much closer to "-vta" than it
is to "-vth". If your lens is equisolidangle, then you need to use the
fisheye_corr.cal script or similar to convert it to an equidistant
projection.

I have not implemented the equisolidangle projection, though there is a
third fisheye type (-vts) which is called "stereographic", although we
prefer the term "planisphere" projection to avoid confusion with stereo
views. This does not correspond to any commercial lenses to my knowledge,
but I'd be interested to hear of one.

> From: Raquel Viula <[email protected]>
> Date: January 27, 2017 5:49:57 AM PST
>
> Hi all,
> Thank you for raising this topic and sharing your views. I?m using the
output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via
Evalglare that should require a -vth or -vta view, so this is critical
information for me.
> May I ask why people refer to -vth as equi-solid angle and not
hemispherical as it is defined in Radiance?s rpict man page?
> My understanding from that page and from Axel Jacobs' presentation sent
via the link just before is that there isn't a Radiance description for the
equi-solid angle view.
>
> Best Regards
>
> Raquel Viula
> PhD Researcher
>
> TU Delft | Faculty of Architecture and the Built Environment |
> Architectural Engineering and Technology
> Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA
Delft
>
> From: Claus Br?ndgaard Madsen <[email protected]>
> Reply-To: High Dynamic Range Imaging <[email protected]>
> Date: Friday 27 January 2017 13:49
> To: High Dynamic Range Imaging <[email protected]>
> Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
>
>
>
> Hi everyone,
>
> Some years ago I tested my Sigma 8mm lens, f3.5.
>
> At the time I found several sources online claiming it to be equi-solid
angle (-vth), but it didn?t match my personal experiences with the lens, so
I tested it.
>
> My tests showed it to be equidistant (-vta), i.e. identical to the
angular fish eye projection in RADIANCE.
>
> So, in my experience, the 8mm Sigma lens is equidistant.
>
> Cheers,
> Claus
>
>
>
> Claus B. Madsen
> Assoc. Prof., Ph.D. | Department of Architecture and Media Technology
>
> Phone: +45 9940 8788 | E-mail: [email protected]
> Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark
>
> Employee No.: 107255 | Vat No.: DK29102384
>
>
> From: "J. Alstan Jakubiec" <[email protected]>
> Reply-To: High Dynamic Range Imaging <[email protected]>
> Date: Friday, 27 January 2017 at 11.33
> To: "[email protected]" <[email protected]>
> Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
>
> A little followup that is worth noting is that Axel Jacobs measured the
Sigma 4.5mm and found it to have an equi-solid angle projection. See his
presentation here: https://www.radiance-online.
org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-
AJ09-HDR_Radiance_WS-2012.pdf
>
> Alstan
>
>
> On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:
> Hi Tobias,
>
> I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't
measured them for vignetting and angular verification yet. It is on my to
do list :). I will be disappointed if they are equi-solid angular however.
Will let you know sometime after the Lunar new year.
>
> Alstan
>
>
> On 1/27/2017 6:17 PM, Tobias Porsch wrote:
> Hi Alstan,
>
> I'm not sure if your below description is correct.
> In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens
is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an
equi-distant (-angular) (-vta) lens.
> Can you please double-check that issue for me?
>
> Cheers
> Tobias
>
> Von: J. Alstan Jakubiec [mailto:[email protected]]
> Gesendet: Donnerstag, 26. Januar 2017 06:58
> An: [email protected]
> Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection
>
> Hi Zhe,
>
> As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)
lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am
having trouble finding a source from Sigma right now, but Cauwerts, Bodart
and Deneyer's paper says so.
>
> That said, if you do end up with an equi-solidangle image, I have a
python script that converts equi-solid angle to equi-angle for each source
jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.
>
> Best,
> Alstan
>
> On 1/26/2017 8:48 AM, Gregory J. Ward wrote:
> Hi Zhe,
>
> You should be able to apply the fisheye_corr.cal file I gave you earlier
to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
suggested in the fisheye_corr.cal file itself:
>
> pcomb -f fisheye_corr.cal -o fisheye.hdr \
> > getinfo -a "VIEW= -vta -vh 180 -vv 180" \
> > corrected.hdr
>
> This will also crop the area outside of 180? to black, assuming that is
what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.
>
> Cheers,
> -Greg
>
> From: Zhe Kong <[email protected]>
> Date: January 25, 2017 1:15:49 PM PST
>
> Dear list:
> I am trying to compare HDR images and simulated luminance maps. Since I
use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:
>
> https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html
>
> However, I still have some questions need to figure out.
> 1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?
>
> 2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?
>
> Any suggestions or explanation would be appreciated.
> Zhe
>
>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
>
>
>
>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
>
>
>
>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
>
>
> _______________________________________________ HDRI mailing list
[email protected] http://www.radiance-online.
org/mailman/listinfo/hdri _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
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***********************************

--
*Zhe Kong*
*PhD Student*
*University of Wisconsin - Milwaukee *
*School of Architecture and Urban Planning *
*2131 E. Hartford Ave, Milwaukee, WI 53211 *
*Office 327*

13

Hi Zhe, I¹m glad you brought this up and thank you Greg for the
clarification.

Best Regards

Raquel

Raquel Viula

PhD Researcher

TU Delft | Faculty of Architecture and the Built Environment |

Architectural Engineering and Technology

Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA Delf

···

From: Zhe Kong <[email protected]>
Reply-To: High Dynamic Range Imaging <[email protected]>
Date: Saturday 28 January 2017 02:09
To: <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Sorry about the confusion I brought up. I got this wrong information from
the manufacturer. If I recall my previous experience, Sigma f/3.5 matches
Radiance -vta pretty well. The current mismatch might be caused by the
camera coordinate in the simulation.
Anyway, Happy Chinese New Year, everyone!

Zhe

On Fri, Jan 27, 2017 at 10:11 AM, <[email protected]> wrote:

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Today's Topics:

   1. Re: Convert equisolidangular to equiangular projection
      (Gregory J. Ward)

----------------------------------------------------------------------

Message: 1
Date: Fri, 27 Jan 2017 08:10:53 -0800
From: "Gregory J. Ward" <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Message-ID: <[email protected]>
Content-Type: text/plain; charset="windows-1252"

Raquel points out an important error in this discussion's terminology. The
"equidistant" fisheye does indeed correspond to the "-vta" view type in
Radiance. However, the "-vth" type corresponds to a hemispherical projection,
which very few commercial fisheye lenses realize. In particular, the
equisolidangle projection is much closer to "-vta" than it is to "-vth". If
your lens is equisolidangle, then you need to use the fisheye_corr.cal script
or similar to convert it to an equidistant projection.

I have not implemented the equisolidangle projection, though there is a third
fisheye type (-vts) which is called "stereographic", although we prefer the
term "planisphere" projection to avoid confusion with stereo views. This does
not correspond to any commercial lenses to my knowledge, but I'd be interested
to hear of one.

> From: Raquel Viula <[email protected]>
> Date: January 27, 2017 5:49:57 AM PST
>
> Hi all,
> Thank you for raising this topic and sharing your views. I?m using the
output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via
Evalglare that should require a -vth or -vta view, so this is critical
information for me.
> May I ask why people refer to -vth as equi-solid angle and not
hemispherical as it is defined in Radiance?s rpict man page?
> My understanding from that page and from Axel Jacobs' presentation sent via
the link just before is that there isn't a Radiance description for the
equi-solid angle view.
>
> Best Regards
>
> Raquel Viula
> PhD Researcher
>
> TU Delft | Faculty of Architecture and the Built Environment |
> Architectural Engineering and Technology
> Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA
Delft
>
> From: Claus Br?ndgaard Madsen <[email protected]>
> Reply-To: High Dynamic Range Imaging <[email protected]>
> Date: Friday 27 January 2017 13:49
> To: High Dynamic Range Imaging <[email protected]>
> Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
>
>
>
> Hi everyone,
>
> Some years ago I tested my Sigma 8mm lens, f3.5.
>
> At the time I found several sources online claiming it to be equi-solid
angle (-vth), but it didn?t match my personal experiences with the lens, so I
tested it.
>
> My tests showed it to be equidistant (-vta), i.e. identical to the angular
fish eye projection in RADIANCE.
>
> So, in my experience, the 8mm Sigma lens is equidistant.
>
> Cheers,
> Claus
>
>
>
> Claus B. Madsen
> Assoc. Prof., Ph.D. | Department of Architecture and Media Technology
>
> Phone: +45 9940 8788 <tel:%2B45%209940%208788> | E-mail: [email protected]
> Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark
>
> Employee No.: 107255 | Vat No.: DK29102384
>
>
> From: "J. Alstan Jakubiec" <[email protected]>
> Reply-To: High Dynamic Range Imaging <[email protected]>
> Date: Friday, 27 January 2017 at 11.33
> To: "[email protected]" <[email protected]>
> Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
>
> A little followup that is worth noting is that Axel Jacobs measured the
Sigma 4.5mm and found it to have an equi-solid angle projection. See his
presentation here:
https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jaco
bs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf
>
> Alstan
>
>
> On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:
> Hi Tobias,
>
> I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't
measured them for vignetting and angular verification yet. It is on my to do
list :). I will be disappointed if they are equi-solid angular however. Will
let you know sometime after the Lunar new year.
>
> Alstan
>
>
> On 1/27/2017 6:17 PM, Tobias Porsch wrote:
> Hi Alstan,
>
> I'm not sure if your below description is correct.
> In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is
an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant
(-angular) (-vta) lens.
> Can you please double-check that issue for me?
>
> Cheers
> Tobias
>
> Von: J. Alstan Jakubiec [mailto:[email protected]]
> Gesendet: Donnerstag, 26. Januar 2017 06:58
> An: [email protected]
> Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection
>
> Hi Zhe,
>
> As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens,
and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having
trouble finding a source from Sigma right now, but Cauwerts, Bodart and
Deneyer's paper says so.
>
> That said, if you do end up with an equi-solidangle image, I have a python
script that converts equi-solid angle to equi-angle for each source jpeg
while maintaining the EXIF data. I used this to convert equi-solidangle
images from my Canon 8-15mm fisheye lenses.
>
> Best,
> Alstan
>
> On 1/26/2017 8:48 AM, Gregory J. Ward wrote:
> Hi Zhe,
>
> You should be able to apply the fisheye_corr.cal file I gave you earlier to
correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
suggested in the fisheye_corr.cal file itself:
>
> pcomb -f fisheye_corr.cal -o fisheye.hdr \
> > getinfo -a "VIEW= -vta -vh 180 -vv 180" \

> > corrected.hdr

>
> This will also crop the area outside of 180? to black, assuming that is
what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.
>
> Cheers,
> -Greg
>
> From: Zhe Kong <[email protected]>
> Date: January 25, 2017 1:15:49 PM PST
>
> Dear list:
> I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular
project. I see very useful information from the post below:
>
>
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/01
1184.html
>
> However, I still have some questions need to figure out.
> 1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the command?
>
> 2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record
the luminance value on a grey card for calibration. My question is, should I
calibrate the image before or after converting fisheye projection?
>
> Any suggestions or explanation would be appreciated.
> Zhe
>
>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
>
>
>
>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
>
>
>
>
> _______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri
>
>
> _______________________________________________ HDRI mailing list
[email protected] http://www.radiance-online.org/mailman/listinfo/hdri
_______________________________________________
> HDRI mailing list
> [email protected]
> http://www.radiance-online.org/mailman/listinfo/hdri

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***********************************

--
Zhe Kong
PhD Student
University of Wisconsin - Milwaukee
School of Architecture and Urban Planning
2131 E. Hartford Ave, Milwaukee, WI 53211
Office 327
_______________________________________________ HDRI mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/hdri

14

Update :

For the projection of the Sigma fisheye lens EX DG 8mm F/3.5, it is an equisolid-angle one!
You should have a look at this post:
https://www.radiance-online.org//pipermail/hdri/2017-February/000617.html<https://www.radiance-online.org/pipermail/hdri/2017-February/000617.html>

Hope this is not too late!

Best,

Clotilde