DGP on 172 fish-eye image

Dear all,
I have a question regarding Evalglare. Hopefully this is the right mailing
list to ask.
Can DGP be calculated for a -vta fish-eye photo capture that has a view
angle of 172 degrees? The manual says that Evalglare can be run for an image
cut horizontally given an externally measured vertical eye illuminance and Y
max and Y min coordinates but does not mention the possibility of using an
image that is also cut vertically, or shall I say, all around.
Thank you for your help.

Best Regards

Raquel

Raquel Viula

PhD candidate

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

Hi Raquel,

I would say yes. Just make sure that the view in the HDR header is appropriate or you specify it inline: evalglare -vta -vv 172 -vh 172 image.hdr

This may slightly underestimate vertical eye illuminance calculated by the software, skewing your results a bit; however, 172 is close enough to 180 in terms of view angle that the error is likely minimal. Still, if you have vertical eye illuminance measurements, supply them inline with the -i flag as well.

Best,

Alstan

···

On 3/14/2017 9:40 PM, Raquel Viula wrote:

Dear all,
I have a question regarding Evalglare. Hopefully this is the right mailing list to ask.
Can DGP be calculated for a -vta fish-eye photo capture that has a view angle of 172 degrees? The manual says that Evalglare can be run for an image cut horizontally given an externally measured vertical eye illuminance and Y max and Y min coordinates but does not mention the possibility of using an image that is also cut vertically, or shall I say, all around.
Thank you for your help.

Best Regards

Raquel

*Raquel Viula*

PhD candidate

*TUDelft | 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

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

Hi Alstan,
That¹s great to know, thank you. Yes, I have vertical eye illuminance
measurements. I think it¹s probably a good idea to estimate what the error
might be via simulation.

Best Regards

Raquel

Raquel Viula

PhD candidate

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: "J. Alstan Jakubiec" <[email protected]>
Reply-To: Radiance general discussion
<[email protected]>
Date: Wednesday 15 March 2017 06:18
To: <[email protected]>
Subject: Re: [Radiance-general] DGP on 172 fish-eye image

Hi Raquel,

I would say yes. Just make sure that the view in the HDR header is
appropriate or you specify it inline: evalglare -vta -vv 172 -vh 172
image.hdr

This may slightly underestimate vertical eye illuminance calculated by the
software, skewing your results a bit; however, 172 is close enough to 180 in
terms of view angle that the error is likely minimal. Still, if you have
vertical eye illuminance measurements, supply them inline with the -i flag
as well.

Best,

Alstan

On 3/14/2017 9:40 PM, Raquel Viula wrote:

Dear all,

I have a question regarding Evalglare. Hopefully this is the right mailing
list to ask.

Can DGP be calculated for a -vta fish-eye photo capture that has a view angle
of 172 degrees? The manual says that Evalglare can be run for an image cut
horizontally given an externally measured vertical eye illuminance and Y max
and Y min coordinates but does not mention the possibility of using an image
that is also cut vertically, or shall I say, all around.

Thank you for your help.

Best Regards

Raquel

Raquel Viula

PhD candidate

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

_______________________________________________
Radiance-general mailing list
[email protected]://www.radiance-online.org/mailman/lis
tinfo/radiance-general

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

Hi Raquel,

I agree that the outer 8� contribute only a little to the vertical illuminance. The solid angle of that section is around 0.44sr (which is around 7% of the total) and the cosinus for this flat angle of incidence is also very low (in average around 0.07). so the overall impact of the outer 8 degree is less than 0.5%, assuming the luminances in that area are comparable to the average of the image .

Regarding the "filling" option in evalglare: this was implemented, because there was a group using a fish-eye lens, where the projected circle was larger in y-direction than the CCD-array. This function "fills up" the missing parts with the last known value vertically. You cannot use it in my opinion to fill up missing "ring" areas (to fill up between 172� to 180�). Actually I could implement such a feature, but due to the low impact I don't think it is necessary and so far no other users were missing such a feature.

Are you really sure you have a equidistant-projecting lens with 172�? The equidistant types are much less frequent on the market - most lenses cover 180� or more.
If you have a equi-solidangle fish-eye lens, you should correct the projection as well.

What you should definitely check is how close you get between measured illuminance with the sensor and the calculated value from evalglare. If you have a deviation there, you have a problem in the calibration (because the influence of the outer 8% is really negligible, so you should nearly match the value ).

BTW: Are you coming to the academic forum of Velux May2nd? As far as I know, there are at least three other PhD students there dealing with HDR-cameras, daylight and glare and as far as I heard there are still free spots. I will be there as well.

best
Jan

···

On 03/15/2017 10:31 AM, Raquel Viula wrote:

Hi Alstan,
That�s great to know, thank you. Yes, I have vertical eye illuminance measurements. I think it�s probably a good idea to estimate what the error might be via simulation.

Best Regards

Raquel

*Raquel Viula*

PhD candidate

*TUDelft | 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: "J. Alstan Jakubiec" <[email protected] <mailto:[email protected]>>
Reply-To: Radiance general discussion <[email protected] <mailto:[email protected]>>
Date: Wednesday 15 March 2017 06:18
To: <[email protected] <mailto:[email protected]>>
Subject: Re: [Radiance-general] DGP on 172 fish-eye image

Hi Raquel,

I would say yes. Just make sure that the view in the HDR header is appropriate or you specify it inline: evalglare -vta -vv 172 -vh 172 image.hdr

This may slightly underestimate vertical eye illuminance calculated by the software, skewing your results a bit; however, 172 is close enough to 180 in terms of view angle that the error is likely minimal. Still, if you have vertical eye illuminance measurements, supply them inline with the -i flag as well.

Best,

Alstan

On 3/14/2017 9:40 PM, Raquel Viula wrote:

Dear all,
I have a question regarding Evalglare. Hopefully this is the right mailing list to ask.
Can DGP be calculated for a -vta fish-eye photo capture that has a view angle of 172 degrees? The manual says that Evalglare can be run for an image cut horizontally given an externally measured vertical eye illuminance and Y max and Y min coordinates but does not mention the possibility of using an image that is also cut vertically, or shall I say, all around.
Thank you for your help.

Best Regards

Raquel

*Raquel Viula*

PhD candidate

*TUDelft | 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

_______________________________________________
Radiance-general mailing list
[email protected]://www.radiance-online.org/mailman/listinfo/radiance-general

_______________________________________________ Radiance-general mailing list [email protected] <mailto:[email protected]> http://www.radiance-online.org/mailman/listinfo/radiance-general

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

--
Dr.-Ing. Jan Wienold
Ecole Polytechnique F�d�rale de Lausanne (EPFL)
EPFL ENAC IA LIPID

http://people.epfl.ch/jan.wienold
LE 1 111 (Office)
Phone +41 21 69 30849

Hi Jan,

Thank you for the clarifications. It all makes much sense and it¹s good to
know that the filling option was developed for those particular projection
conditions. I totally understand that if I¹m the only user with this problem
it does probably not worth your time to add that to Evalglare.
But that also means that there is no reason why I could not use the DGP
formula to make the calculation of a fish-eye image with these
characteristics elsewhere, correct?

I wanted to check with TechnoTeam, again, before getting back to you about
the specifications of my system. And indeed according to them my projection
is of an equidistant-type with a view angle of 172.

I noticed that my vertical eye illuminance measurements have a bit of a time
offset from the pictures, so really not appropriate to check for the
deviation. I¹ll get new values to test next week. But this also involves
using a newly created TechnoTeam¹s Radiance exporter which it is still under
validationŠso there are few things to get right in order to make this test
possible. I will get back to the list when I have a conclusion.

I¹ll see if I can still come to VeluxŠI had to make a choice because there
are so many other important events that one can attend this year. But it
would be really important to discuss this with you and the other PhDs.

Best Regards

Raquel

Raquel Viula

PhD candidate

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: Jan Wienold <[email protected]>
Reply-To: Radiance general discussion
<[email protected]>
Date: Wednesday 15 March 2017 19:40
To: Radiance general discussion <[email protected]>
Subject: Re: [Radiance-general] DGP on 172 fish-eye image

Hi Raquel,

I agree that the outer 8° contribute only a little to the vertical
illuminance. The solid angle of that section is around 0.44sr (which is
around 7% of the total) and the cosinus for this flat angle of incidence is
also very low (in average around 0.07). so the overall impact of the outer 8
degree is less than 0.5%, assuming the luminances in that area are
comparable to the average of the image .
  
Regarding the "filling" option in evalglare: this was implemented, because
there was a group using a fish-eye lens, where the projected circle was
larger in y-direction than the CCD-array. This function "fills up" the
missing parts with the last known value vertically. You cannot use it in my
opinion to fill up missing "ring" areas (to fill up between 172° to 180°).
Actually I could implement such a feature, but due to the low impact I don't
think it is necessary and so far no other users were missing such a feature.

Are you really sure you have a equidistant-projecting lens with 172°? The
equidistant types are much less frequent on the market - most lenses cover
180° or more.
If you have a equi-solidangle fish-eye lens, you should correct the
projection as well.

What you should definitely check is how close you get between measured
illuminance with the sensor and the calculated value from evalglare. If you
have a deviation there, you have a problem in the calibration (because the
influence of the outer 8% is really negligible, so you should nearly match
the value ).

BTW: Are you coming to the academic forum of Velux May2nd? As far as I
know, there are at least three other PhD students there dealing with
HDR-cameras, daylight and glare and as far as I heard there are still free
spots. I will be there as well.

best
Jan

On 03/15/2017 10:31 AM, Raquel Viula wrote:

Hi Alstan,

That¹s great to know, thank you. Yes, I have vertical eye illuminance
measurements. I think it¹s probably a good idea to estimate what the error
might be via simulation.

Best Regards

Raquel

Raquel Viula

PhD candidate

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: "J. Alstan Jakubiec" <[email protected]>
Reply-To: Radiance general discussion <[email protected]>
Date: Wednesday 15 March 2017 06:18
To: <[email protected]>
Subject: Re: [Radiance-general] DGP on 172 fish-eye image

Hi Raquel,

I would say yes. Just make sure that the view in the HDR header is appropriate
or you specify it inline: evalglare -vta -vv 172 -vh 172 image.hdr

This may slightly underestimate vertical eye illuminance calculated by the
software, skewing your results a bit; however, 172 is close enough to 180 in
terms of view angle that the error is likely minimal. Still, if you have
vertical eye illuminance measurements, supply them inline with the -i flag as
well.

Best,

Alstan

On 3/14/2017 9:40 PM, Raquel Viula wrote:

Dear all,

I have a question regarding Evalglare. Hopefully this is the right mailing
list to ask.

Can DGP be calculated for a -vta fish-eye photo capture that has a view angle
of 172 degrees? The manual says that Evalglare can be run for an image cut
horizontally given an externally measured vertical eye illuminance and Y max
and Y min coordinates but does not mention the possibility of using an image
that is also cut vertically, or shall I say, all around.

Thank you for your help.

Best Regards

Raquel

Raquel Viula

PhD candidate

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

_______________________________________________
Radiance-general mailing list
[email protected]://www.radiance-online.org/mailman/li
stinfo/radiance-general

_______________________________________________ Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general
  
_______________________________________________
Radiance-general mailing list
[email protected]://www.radiance-online.org/mailman/lis
tinfo/radiance-general

--
Dr.-Ing. Jan Wienold
Ecole Polytechnique Fédérale de Lausanne (EPFL)
EPFL ENAC IA LIPID

http://people.epfl.ch/jan.wienold
LE 1 111 (Office)
Phone +41 21 69 30849

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