Photosphere "Cannot solve for response function"

Dear all,

I am trying to create HDRIs using an Android Smartphone. I have taken six photos ranging from –3 to +3 and have tried to fuse these in Photosphere, however I am getting a “cannot solve for response function” message. Does anyone know how I can create a response curve or what I am missing to create the response curve? I can create a HDR image using the generic response curve, but for my thesis I would need all the HDRIs to be as accurate as possible.

Thank you for your time.

Kind regards,
Peony

- -
Peony Au
Masters of Building Science Candidate
Victoria University of Wellington
New Zealand

Mobile (+64) (0)277514389

Hi Peony,

The likely problem is that your smart phone is too smart! Most phone cameras play tricks with the response curve, white balance, and other capture characteristics that undermine any attempt to get a consistent HDR result. No phone cameras I know allow you a true "manual mode" that disables such behavior, so they aren't really suited to HDR capture.

Best,
-Greg

···

From: "Peony Au" <[email protected]>
Date: August 23, 2012 1:50:24 AM PDT

Dear all,

I am trying to create HDRIs using an Android Smartphone. I have taken six photos ranging from –3 to +3 and have tried to fuse these in Photosphere, however I am getting a “cannot solve for response function” message. Does anyone know how I can create a response curve or what I am missing to create the response curve? I can create a HDR image using the generic response curve, but for my thesis I would need all the HDRIs to be as accurate as possible.

Thank you for your time.

Kind regards,
Peony

Haha Greg, isn't another likely problem camera movement between exposures?

- Rob

···

On Aug 23, 2012, at 11:25 AM, Gregory J. Ward wrote:

Hi Peony,

The likely problem is that your smart phone is too smart! Most phone cameras play tricks with the response curve, white balance, and other capture characteristics that undermine any attempt to get a consistent HDR result. No phone cameras I know allow you a true "manual mode" that disables such behavior, so they aren't really suited to HDR capture.

Best,
-Greg

From: "Peony Au" <[email protected]>
Date: August 23, 2012 1:50:24 AM PDT

Dear all,

I am trying to create HDRIs using an Android Smartphone. I have taken six photos ranging from –3 to +3 and have tried to fuse these in Photosphere, however I am getting a “cannot solve for response function” message. Does anyone know how I can create a response curve or what I am missing to create the response curve? I can create a HDR image using the generic response curve, but for my thesis I would need all the HDRIs to be as accurate as possible.

Thank you for your time.

Kind regards,
Peony

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

Well, Photosphere is supposed to handle some camera motion, but if you're shooting from your bicycle....

···

From: Rob Guglielmetti <[email protected]>
Date: August 23, 2012 10:34:49 AM PDT

Haha Greg, isn't another likely problem camera movement between exposures?

- Rob

On Aug 23, 2012, at 11:25 AM, Gregory J. Ward wrote:

Hi Peony,

The likely problem is that your smart phone is too smart! Most phone cameras play tricks with the response curve, white balance, and other capture characteristics that undermine any attempt to get a consistent HDR result. No phone cameras I know allow you a true "manual mode" that disables such behavior, so they aren't really suited to HDR capture.

Best,
-Greg

From: "Peony Au" <[email protected]>
Date: August 23, 2012 1:50:24 AM PDT

Dear all,

I am trying to create HDRIs using an Android Smartphone. I have taken six photos ranging from –3 to +3 and have tried to fuse these in Photosphere, however I am getting a “cannot solve for response function” message. Does anyone know how I can create a response curve or what I am missing to create the response curve? I can create a HDR image using the generic response curve, but for my thesis I would need all the HDRIs to be as accurate as possible.

Thank you for your time.

Kind regards,
Peony

_______________________________________________
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

Hi Greg & Rob,

Thank you for your quick responses. I've taken the photos on a tripod under an artificial sky to minimise errors, but from what you are saying there's nothing I can do to create a camera response curve.

Thank you for all your help.

Kind regards,
Peony

···

-----Original Message----- From: Gregory J. Ward
Sent: Friday, August 24, 2012 6:11 AM
To: High Dynamic Range Imaging
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Well, Photosphere is supposed to handle some camera motion, but if you're shooting from your bicycle....

From: Rob Guglielmetti <[email protected]>
Date: August 23, 2012 10:34:49 AM PDT

Haha Greg, isn't another likely problem camera movement between exposures?

- Rob

On Aug 23, 2012, at 11:25 AM, Gregory J. Ward wrote:

Hi Peony,

The likely problem is that your smart phone is too smart! Most phone cameras play tricks with the response curve, white balance, and other capture characteristics that undermine any attempt to get a consistent HDR result. No phone cameras I know allow you a true "manual mode" that disables such behavior, so they aren't really suited to HDR capture.

Best,
-Greg

From: "Peony Au" <[email protected]>
Date: August 23, 2012 1:50:24 AM PDT

Dear all,

I am trying to create HDRIs using an Android Smartphone. I have taken six photos ranging from –3 to +3 and have tried to fuse these in Photosphere, however I am getting a “cannot solve for response function” message. Does anyone know how I can create a response curve or what I am missing to create the response curve? I can create a HDR image using the generic response curve, but for my thesis I would need all the HDRIs to be as accurate as possible.

Thank you for your time.

Kind regards,
Peony

_______________________________________________
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

Peony,

It is also possible that you could not create the camera response curve based on the scene you have taken. If the scene does not have large and smooth gradients, Photosphere cannot create a camera response curve. This could happen with any camera. A different scene that has the gradients would provide a camera response curve. However, the issues Greg pointed out are major problems with phone cameras. Even if you are able to generate the camera response curve with another scene, due to the inconsistencies Greg pointed out, it is unlikely to get accurate, reliable HDR images.

Mehlika

···

On Fri, 24 Aug 2012, Peony Au wrote:

Hi Greg & Rob,

Thank you for your quick responses. I've taken the photos on a tripod under an artificial sky to minimise errors, but from what you are saying there's nothing I can do to create a camera response curve.

Thank you for all your help.

Kind regards,
Peony

-----Original Message----- From: Gregory J. Ward
Sent: Friday, August 24, 2012 6:11 AM
To: High Dynamic Range Imaging
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Well, Photosphere is supposed to handle some camera motion, but if you're shooting from your bicycle....

From: Rob Guglielmetti <[email protected]>
Date: August 23, 2012 10:34:49 AM PDT

Haha Greg, isn't another likely problem camera movement between exposures?

- Rob

On Aug 23, 2012, at 11:25 AM, Gregory J. Ward wrote:

Hi Peony,

The likely problem is that your smart phone is too smart! Most phone cameras play tricks with the response curve, white balance, and other capture characteristics that undermine any attempt to get a consistent HDR result. No phone cameras I know allow you a true "manual mode" that disables such behavior, so they aren't really suited to HDR capture.

Best,
-Greg

From: "Peony Au" <[email protected]>
Date: August 23, 2012 1:50:24 AM PDT

Dear all,

I am trying to create HDRIs using an Android Smartphone. I have taken six photos ranging from –3 to +3 and have tried to fuse these in Photosphere, however I am getting a “cannot solve for response function” message. Does anyone know how I can create a response curve or what I am missing to create the response curve? I can create a HDR image using the generic response curve, but for my thesis I would need all the HDRIs to be as accurate as possible.

Thank you for your time.

Kind regards,
Peony

_______________________________________________
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

Hi Peony,

if you upload your sequence to
http://www.jaloxa.eu/webhdr/roll-your-own.shtml
I'll have a look over the weekend. However, as Greg pointed out--don't hold your breath. You might have to use a proper camera if you're interested in HDRs that are 'as accurate as possible'. What are you trying to measure?

Cheers

Axel

···

On 08/23/2012 09:50 AM, Peony Au wrote:

Dear all,
I am trying to create HDRIs using an Android Smartphone. I have taken
six photos ranging from –3 to +3 and have tried to fuse these in
Photosphere, however I am getting a “cannot solve for response function”
message. Does anyone know how I can create a response curve or what I am
missing to create the response curve? I can create a HDR image using the
generic response curve, but for my thesis I would need all the HDRIs to
be as accurate as possible.
Thank you for your time.
Kind regards,
Peony
- -
Peony Au
Masters of Building Science Candidate
Victoria University of Wellington
New Zealand

Mobile (+64) (0)277514389

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

Hi Axel,

Thank you for that. Have uploaded a sequence onto your website.
I'm trying to determine if a Smartphone is able to capture a HDR scene as a daylight analysis tool.

Thank you for all your time.

Kind regards,
Peony

···

-----Original Message----- From: Axel Jacobs
Sent: Friday, August 24, 2012 11:16 AM
To: [email protected]
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Hi Peony,

if you upload your sequence to
http://www.jaloxa.eu/webhdr/roll-your-own.shtml
I'll have a look over the weekend. However, as Greg pointed out--don't
hold your breath. You might have to use a proper camera if you're
interested in HDRs that are 'as accurate as possible'. What are you
trying to measure?

Cheers

Axel

On 08/23/2012 09:50 AM, Peony Au wrote:

Dear all,
I am trying to create HDRIs using an Android Smartphone. I have taken
six photos ranging from –3 to +3 and have tried to fuse these in
Photosphere, however I am getting a “cannot solve for response function”
message. Does anyone know how I can create a response curve or what I am
missing to create the response curve? I can create a HDR image using the
generic response curve, but for my thesis I would need all the HDRIs to
be as accurate as possible.
Thank you for your time.
Kind regards,
Peony
- -
Peony Au
Masters of Building Science Candidate
Victoria University of Wellington
New Zealand

Mobile (+64) (0)277514389

_______________________________________________
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

Hi Peony,

The four images that you uploaded have the following exposure values:

0.jpg ISO68 F2.8 0.0666667s 6.32EV
1.jpg ISO199 F2.8 0.0666667s 7.87EV
2.jpg ISO200 F2.8 0.125s 6.97EV
3.jpg ISO200 F2.8 0.125s 6.97EV

You need a wider range of exposures to cover the dynamic range of the scene. Visually, the images appear to have almost the same brightness. They need to noticeable different. See
http://www.jaloxa.eu/webhdr/demo.shtml
for an example exposure-bracketed sequence.

It is recommended to vary only the exposure time, although in principle, playing with the ISO sensitivity should work, too. Just make sure the aperture is fixed, which it is in your example shots.

The last two images (I don't have your original file names) have exactly the same exposure. Visually, however, one is a little darker than the other. This can mean that the EXIF information (aperture, ISO, shutter) is unreliable.

You must also mount your camera/smart phone on a tripod. hdrgen can do some magic trying to align the frames, but it's better to not rely on it. For accurate results, a tripod is a must.

You will also need to get hold of a luminance meter against which you need to calibrate the HDRs. Note that the calibration factor depends on the white balance setting with which the images were taken.

I don't know how you can control the exposure times on a smartphone, but my recommendation would be that you borrow a decent camera and get some experience with HDR photography before attempting to do this on a smart phone. Alternatively, invest in a second hand Canon PowerShot and put CHDK on it: http://chdk.wikia.com/wiki/CHDK. Make sure your model is supported. This will allow you to take exposure-bracketed sequences without touching the camera. For most PowerShots, it will also give you the option of saving in RAW format for when you need the results to be VERY accurate.

Hope this gets you started. Good luck

Axel

···

From: Axel Jacobs
Sent: Friday, August 24, 2012 11:16 AM
To: [email protected]
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Hi Peony,

if you upload your sequence to
http://www.jaloxa.eu/webhdr/roll-your-own.shtml
I'll have a look over the weekend. However, as Greg pointed out--don't
hold your breath. You might have to use a proper camera if you're
interested in HDRs that are 'as accurate as possible'. What are you
trying to measure?

Cheers

Axel

On 08/23/2012 09:50 AM, Peony Au wrote:

Dear all,
I am trying to create HDRIs using an Android Smartphone. I have taken
six photos ranging from –3 to +3 and have tried to fuse these in
Photosphere, however I am getting a “cannot solve for response function”
message. Does anyone know how I can create a response curve or what I am
missing to create the response curve? I can create a HDR image using the
generic response curve, but for my thesis I would need all the HDRIs to
be as accurate as possible.

Hi Axel,

Thank you for all your help. It is greatly appreciated.

Kind regards,
Peony

···

Date: Sun, 26 Aug 2012 12:13:47 +0100
From: [email protected]
To: [email protected]
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Hi Peony,

The four images that you uploaded have the following exposure values:

0.jpg ISO68 F2.8 0.0666667s 6.32EV
1.jpg ISO199 F2.8 0.0666667s 7.87EV
2.jpg ISO200 F2.8 0.125s 6.97EV
3.jpg ISO200 F2.8 0.125s 6.97EV

You need a wider range of exposures to cover the dynamic range of the
scene. Visually, the images appear to have almost the same brightness.
They need to noticeable different. See
http://www.jaloxa.eu/webhdr/demo.shtml
for an example exposure-bracketed sequence.

It is recommended to vary only the exposure time, although in principle,
playing with the ISO sensitivity should work, too. Just make sure the
aperture is fixed, which it is in your example shots.

The last two images (I don't have your original file names) have exactly
the same exposure. Visually, however, one is a little darker than the
other. This can mean that the EXIF information (aperture, ISO, shutter)
is unreliable.

You must also mount your camera/smart phone on a tripod. hdrgen can do
some magic trying to align the frames, but it's better to not rely on
it. For accurate results, a tripod is a must.

You will also need to get hold of a luminance meter against which you
need to calibrate the HDRs. Note that the calibration factor depends on
the white balance setting with which the images were taken.

I don't know how you can control the exposure times on a smartphone, but
my recommendation would be that you borrow a decent camera and get some
experience with HDR photography before attempting to do this on a smart
phone. Alternatively, invest in a second hand Canon PowerShot and put
CHDK on it: http://chdk.wikia.com/wiki/CHDK. Make sure your model is
supported. This will allow you to take exposure-bracketed sequences
without touching the camera. For most PowerShots, it will also give you
the option of saving in RAW format for when you need the results to be
VERY accurate.

Hope this gets you started. Good luck

Axel

> From: Axel Jacobs
> Sent: Friday, August 24, 2012 11:16 AM
> To: [email protected]
> Subject: Re: [HDRI] Photosphere "Cannot solve for response function"
>
> Hi Peony,
>
> if you upload your sequence to
> http://www.jaloxa.eu/webhdr/roll-your-own.shtml
> I'll have a look over the weekend. However, as Greg pointed out--don't
> hold your breath. You might have to use a proper camera if you're
> interested in HDRs that are 'as accurate as possible'. What are you
> trying to measure?
>
> Cheers
>
> Axel
>
>
> On 08/23/2012 09:50 AM, Peony Au wrote:
>> Dear all,
>> I am trying to create HDRIs using an Android Smartphone. I have taken
>> six photos ranging from –3 to +3 and have tried to fuse these in
>> Photosphere, however I am getting a “cannot solve for response function”
>> message. Does anyone know how I can create a response curve or what I am
>> missing to create the response curve? I can create a HDR image using the
>> generic response curve, but for my thesis I would need all the HDRIs to
>> be as accurate as possible.

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

Dear all,

After a discussion with my supervisor, there are a few things I would like to clarify and hopefully get some help on.

Through the built-in app on my Smartphone, I can get seven photographs ranging from EV - 3 to + 3 and I can manually adjust the white balance in the photographs.

I have also captured 3 photographs using a app called HDR camera, but for some reason it was producing 4 photographs on my phone hence the photographs providing the same EV when I uploaded to Axel's website, so I apologise for that. I have emailed the developers and am waiting for an reply for them regarding this.

I've been capturing the images in an artificial sky in a lighting laboratory available at the university and have used a luminance meter to calibrate the images.

And my goal for this thesis is to develop a programmable data acquisition system that is not expensive like a DSLR camera with a fisheye lens, but instead a less expensive method using an Android Smartphone plus a US$50 fisheye lens.

However, though all the process described above, a camera response curve cannot be create and the error message (Cannot solve for response function) appears.
Is there anything else, apart from switching to a DSLR camera, I can do to create a camera response curve?

Thank you for your time.

Kind regards,
Peony

···

-----Original Message----- From: Axel Jacobs
Sent: Sunday, August 26, 2012 11:13 PM
To: [email protected]
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Hi Peony,

The four images that you uploaded have the following exposure values:

0.jpg ISO68 F2.8 0.0666667s 6.32EV
1.jpg ISO199 F2.8 0.0666667s 7.87EV
2.jpg ISO200 F2.8 0.125s 6.97EV
3.jpg ISO200 F2.8 0.125s 6.97EV

You need a wider range of exposures to cover the dynamic range of the
scene. Visually, the images appear to have almost the same brightness.
They need to noticeable different. See
http://www.jaloxa.eu/webhdr/demo.shtml
for an example exposure-bracketed sequence.

It is recommended to vary only the exposure time, although in principle,
playing with the ISO sensitivity should work, too. Just make sure the
aperture is fixed, which it is in your example shots.

The last two images (I don't have your original file names) have exactly
the same exposure. Visually, however, one is a little darker than the
other. This can mean that the EXIF information (aperture, ISO, shutter)
is unreliable.

You must also mount your camera/smart phone on a tripod. hdrgen can do
some magic trying to align the frames, but it's better to not rely on
it. For accurate results, a tripod is a must.

You will also need to get hold of a luminance meter against which you
need to calibrate the HDRs. Note that the calibration factor depends on
the white balance setting with which the images were taken.

I don't know how you can control the exposure times on a smartphone, but
my recommendation would be that you borrow a decent camera and get some
experience with HDR photography before attempting to do this on a smart
phone. Alternatively, invest in a second hand Canon PowerShot and put
CHDK on it: http://chdk.wikia.com/wiki/CHDK. Make sure your model is
supported. This will allow you to take exposure-bracketed sequences
without touching the camera. For most PowerShots, it will also give you
the option of saving in RAW format for when you need the results to be
VERY accurate.

Hope this gets you started. Good luck

Axel

From: Axel Jacobs
Sent: Friday, August 24, 2012 11:16 AM
To: [email protected]
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Hi Peony,

if you upload your sequence to
http://www.jaloxa.eu/webhdr/roll-your-own.shtml
I'll have a look over the weekend. However, as Greg pointed out--don't
hold your breath. You might have to use a proper camera if you're
interested in HDRs that are 'as accurate as possible'. What are you
trying to measure?

Cheers

Axel

On 08/23/2012 09:50 AM, Peony Au wrote:

Dear all,
I am trying to create HDRIs using an Android Smartphone. I have taken
six photos ranging from –3 to +3 and have tried to fuse these in
Photosphere, however I am getting a “cannot solve for response function”
message. Does anyone know how I can create a response curve or what I am
missing to create the response curve? I can create a HDR image using the
generic response curve, but for my thesis I would need all the HDRIs to
be as accurate as possible.

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

Hi Peony!

Is there anything else, apart from switching to a DSLR camera, I can do
to create a camera response curve?

I guess there is something in between mobile phones and DSLR. There are
compact cameras around, some of which can be remote controlled.

Cheers, Lars.

Hi everyone,

After much development on my thesis, I have a few queries I am hoping some of you will be able to help me out on.

First of, my supervisor pointed out an application on the iPhone called iPhotoLux which maps the luminance measurement of an HDR image taken by the iPhone camera. So I am hoping what I am trying to produce in my thesis does work.

Secondly, I have been using a Nikon DSLR camera to create HDR images in the lighting laboratory using a scale model, so that my skills in creating a accurate HDR image. I have also used both luminance and illuminance meters to ensure the photos are accurate.

Therefore, after experimenting in the lighting laboratory, I got my Smartphone camera back out and using a HDR Camera application available in the Android market. I put both cameras side by side and took images of the same scene on a tripod. However, I am still receiving the same error message as before, then I found out that the HDR Camera application does not write the EXIF data required to create a camera response curve. Therefore, just to try the images produced by the Smartphone out, I coped the EXIF data from the DSLR camera and inserted into the images produced by the Smartphone camera ensuring that all the exposure value information are the same. I then try and fuse these Smartphone camera produced images together, but the same error message reappears.

Therefore, I was just wondering if anyone knows why the camera response curve cannot be created even with the comparison done between the DSLR camera and the Smartphone camera.

Thank you for all your help.

Kind regards,
Peony

···

--
Peony Au
Masters of Building Science Candidate
Victoria University of Wellington
New Zealand

Mobile (+64) (0)277514389

-----Original Message----- From: Lars O. Grobe
Sent: Tuesday, August 28, 2012 12:59 AM
To: High Dynamic Range Imaging
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"

Hi Peony!

Is there anything else, apart from switching to a DSLR camera, I can do
to create a camera response curve?

I guess there is something in between mobile phones and DSLR. There are
compact cameras around, some of which can be remote controlled.

Cheers, Lars.

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

Hi Peony,

I guess no one ever responded to this... I can really only repeat my response from August, which is that getting calibrated output from phone cameras is not possible at this stage, and may never be. Their application is too different, and repeatability is not one of the design requirements for these modules. They alter sensitivity, color response, and probably tone response without making any record of the original data. I really think it is a waste of your time.

Best,
-Greg

···

From: "Peony Au" <[email protected]>
Date: November 27, 2012 11:13:11 PM PST

Hi everyone,

After much development on my thesis, I have a few queries I am hoping some of you will be able to help me out on.

First of, my supervisor pointed out an application on the iPhone called iPhotoLux which maps the luminance measurement of an HDR image taken by the iPhone camera. So I am hoping what I am trying to produce in my thesis does work.

Secondly, I have been using a Nikon DSLR camera to create HDR images in the lighting laboratory using a scale model, so that my skills in creating a accurate HDR image. I have also used both luminance and illuminance meters to ensure the photos are accurate.

Therefore, after experimenting in the lighting laboratory, I got my Smartphone camera back out and using a HDR Camera application available in the Android market. I put both cameras side by side and took images of the same scene on a tripod. However, I am still receiving the same error message as before, then I found out that the HDR Camera application does not write the EXIF data required to create a camera response curve. Therefore, just to try the images produced by the Smartphone out, I coped the EXIF data from the DSLR camera and inserted into the images produced by the Smartphone camera ensuring that all the exposure value information are the same. I then try and fuse these Smartphone camera produced images together, but the same error message reappears.

Therefore, I was just wondering if anyone knows why the camera response curve cannot be created even with the comparison done between the DSLR camera and the Smartphone camera.

Thank you for all your help.

Kind regards,
Peony

Hi

I am (finally) back from summer holidays and cannot help but add my twopence worth - as the supervisor Peony refers to.

Peony seems to have narrowed down the problem to a jpeg format issue that makes the image unreadable, nothing to do with the phone itself.

For example, she is able - using the same HDR software on her tablet to generate a camera response curve.

The software for the phone that she is using to generate the HDR images allows the turning of off auto white balance and allows the setting up of 3, 5 or 7 images at separate exposure values.

She can clearly create the camera response curve for the $2000 Nikon camera with its $2000 fish eye lens

With her $300 phone and $50 fish eye lens, and the same software as the tablet she cannot create a curve.

The software saves the original jpg images as well as the combined HDR image on each machine.

At first we thought it was inadequate EXIF data in the original jpeg images. However, it is not the EXIF data because the Nikon camera images with the phone image EXIF data replacing the Nikon's EXIF data still produce a camera response curve.

She has eliminated the jpg image compression from the question because she has opened each jpg original in photoshop and re-saved it in a standard jpg format - the Nikon images still work, the phone not.

Personally, I'd like this to work because first year and second year building science student measurement exercises could be so much more interesting if we were measuring a whole space, not a simple grid... Also: We can calibrate the sound level meters on the phones. They can use a simple app on the phones to photograph the horizon line with overlaid sun path diagrams in Augmented Reality mode. The phone as general survey instrument, not just site camera is becoming a reality. Calibration / trust of each phone, and how to test it is the issue

At another level, I feel responsible for understanding what the issue might be to try to explain what might be going wrong so a) Peony can understand, and document this process properly in her thesis Appendix and b) some recommendations can be formulated as to what camera-phone characteristics to look for.

Thus I return to the question: what might we be unable to control with the phone, but is controlled on the tablet, that would cause this kind of Photosphere error message? And how might we further test what we are doing?

Thanks in anticipation of any help.

M

···

------------------------------------
Victoria University of Wellington School of Architecture
Michael Donn
[email protected]
PO Box 600
139 Vivian St
Wellington
New Zealand
tel: +64 4 463 6221
fax: +64 4 463 6204
mobile: +64 21 611 280
Skype ID:the_donn
------------------------------------

Today's Topics:

   1. Re: Photosphere "Cannot solve for response function"
      (Gregory J. Ward)

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Message: 1
Date: Mon, 24 Dec 2012 08:56:34 -0800
From: "Gregory J. Ward" <[email protected]>
To: High Dynamic Range Imaging <[email protected]>
Subject: Re: [HDRI] Photosphere "Cannot solve for response function"
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii

Hi Peony,

I guess no one ever responded to this... I can really only repeat my response from August, which is that getting calibrated output from phone cameras is not possible at this stage, and may never be. Their application is too different, and repeatability is not one of the design requirements for these modules. They alter sensitivity, color response, and probably tone response without making any record of the original data. I really think it is a waste of your time.

Best,
-Greg

From: "Peony Au" <[email protected]>
Date: November 27, 2012 11:13:11 PM PST

Hi everyone,

After much development on my thesis, I have a few queries I am hoping some of you will be able to help me out on.

First of, my supervisor pointed out an application on the iPhone called iPhotoLux which maps the luminance measurement of an HDR image taken by the iPhone camera. So I am hoping what I am trying to produce in my thesis does work.

Secondly, I have been using a Nikon DSLR camera to create HDR images in the lighting laboratory using a scale model, so that my skills in creating a accurate HDR image. I have also used both luminance and illuminance meters to ensure the photos are accurate.

Therefore, after experimenting in the lighting laboratory, I got my Smartphone camera back out and using a HDR Camera application available in the Android market. I put both cameras side by side and took images of the same scene on a tripod. However, I am still receiving the same error message as before, then I found out that the HDR Camera application does not write the EXIF data required to create a camera response curve. Therefore, just to try the images produced by the Smartphone out, I coped the EXIF data from the DSLR camera and inserted into the images produced by the Smartphone camera ensuring that all the exposure value information are the same. I then try and fuse these Smartphone camera produced images together, but the same error message reappears.

Therefore, I was just wondering if anyone knows why the camera response curve cannot be created even with the comparison done between the DSLR camera and the Smartphone camera.

Thank you for all your help.

Kind regards,
Peony

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End of HDRI Digest, Vol 54, Issue 2
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