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Author Topic: DCamProf - a new camera profiling tool  (Read 767290 times)

Bip

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Re: DCamProf - a new camera profiling tool
« Reply #780 on: August 28, 2015, 05:52:47 pm »

GM data from PM attached
Thank you.

for a start you can use CC24 data embedded into DCamProf itself... I test on that small virtual target initially.
yes, to begin, it is alright.
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AlterEgo

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Re: DCamProf - a new camera profiling tool
« Reply #781 on: August 28, 2015, 05:55:17 pm »

yes, to begin, it is alright.
but then it is totally up to you... I might be happy even with adobergb-grid target for my purposes.
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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #782 on: August 29, 2015, 06:56:46 am »

but then it is totally up to you... I might be happy even with adobergb-grid target for my purposes.
yes, a profile with adobe RGB is already well. I will return my ideas when I have a few profiles with SSF method.
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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #783 on: August 29, 2015, 11:53:19 am »



Do you know why the gamut of icc profiles (for APN) defined in the XYZ space are larger ones defined in space CIE Lab?
I found that with several profilers without understanding even if the equations give the possibility to move from one space to another.
The difference between the 2 spaces being that CIE Lab is perceptual intent rendering.
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torger

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Re: DCamProf - a new camera profiling tool
« Reply #784 on: August 29, 2015, 03:26:16 pm »

Do you know why the gamut of icc profiles (for APN) defined in the XYZ space are larger ones defined in space CIE Lab?
I found that with several profilers without understanding even if the equations give the possibility to move from one space to another.
The difference between the 2 spaces being that CIE Lab is perceptual intent rendering.

The ICC gamut for a camera does not really say much about what real colors the camera actually can capture. A camera is an input device, and you can't see the gamut the same way as for an output device such as a printer or a display.

A ICC Lab LUT will take raw RGB inputs and convert to Lab output, that is 3 values in 3 values out -- a 3D LUT. The LUT needs to cover all combinations of input values (with a limited resolution). As a camera have overlapping color filters it's impossible to get an input signal with say 100% green an 0% red and blue, but that still needs to have some output value in the LUT.

Actually this has been a very hard problem for when designing DCamProf, say 30% of all LUT values are invalid colors and since the calibration makes a model based on real colors and interpolate the rest, the impossible input value combinations get thrown out to crazy positions way outside the human locus, negative lightness and such things. First I just clipped those values, but in practice you then get an "unstable" ICC profile which can lead to strange color effects when you apply an extreme white balance (which may make some of those "impossible" input combinations arise). So I had to fake the impossible values by a special type of interpolation that makes sure that you get sane color output also for insane inputs. It seems like most other profile designers does the same thing in one way or another.

Try pulling the white balance slider to the lowest temperature possible (that will make the whole image blue) and see how the ICC profile behaves. If you have a profile that haven't cared to interpolate outputs the "impossible" inputs, you will probably see colors get clipped to black and possibly get thrown into totally different colors like green, magenta or yellow rather than staying blue.

A LUT can also have XYZ output rather than Lab, but it's not as common so I assume when you refer to XYZ you think about matrix profiles. In this case there's just a simple matrix multiplication that makes the colors, and the matrix has been optimized to produce sane colors in the range it was profiled for, typically a CC24 or similar. It means that for extreme input values you will get crazy output values. The corners of the "gamut triangle" you see in an ICC viewer are 100% green, 100% red and 100% blue, and you can't really reach those points with real inputs, and even if you could the matrix will map those to crazy positions for sure as it has been optimized to make normal colors correct, and that will cause highly saturated colors to get to bad positions.

So in other words, the gamut you see in a camera profile doesn't say anything about the camera's ability to capture colors.
With DCamProf I made a color separation analysis function that can give you some insights into how well the camera can separate colors: http://www.ludd.ltu.se/~torger/dcamprof.html#ssf_csep

It's common to say that "a camera doesn't have a gamut", and sure it does not have a gamut in the same well-defined way as a printer+paper, but it does have limitations concerning color separation. There is no standardized way to define those limits though, and unfortunately you can't get any of that information from the ICC profile.

Of course the ICC profile won't output values outside it's gamut, so you know what values you can't get, but you cannot see which values that represent those "impossible" combinations and thus are meaningless parts of the gamut.
« Last Edit: August 29, 2015, 03:40:44 pm by torger »
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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #785 on: August 29, 2015, 05:33:27 pm »

The ICC gamut for a camera does not really say much about what real colors the camera actually can capture. A camera is an input device, and you can't see the gamut the same way as for an output device such as a printer or a display.

[...]

Torger, thank you for this detailed answer. I did not think asking this question the answer would lead you to give as much precision on the design profiler, but I understand the ideas you give. It is very interesting and there is not these details in books.

When I spoke gamut size (L * a * b / XYZ), I thought of the -p option of make-icc and selects Lablut, XYZlut or matrix. With Copra3 (similar to Colorthink, 3D / 2D viewer), when I look at the size of gamut, I noticed that the volume (3D) or surface (2D) colors (gamut) is more important with a XYZlut profile than Lablut profile.

I also find that the matrix profiles are a little less accurate for correcting delta E 2000, but gives made more smooth (more natural colors) on the pictures.
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torger

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Re: DCamProf - a new camera profiling tool
« Reply #786 on: August 30, 2015, 04:15:24 am »

Torger, thank you for this detailed answer. I did not think asking this question the answer would lead you to give as much precision on the design profiler, but I understand the ideas you give. It is very interesting and there is not these details in books.

When I spoke gamut size (L * a * b / XYZ), I thought of the -p option of make-icc and selects Lablut, XYZlut or matrix. With Copra3 (similar to Colorthink, 3D / 2D viewer), when I look at the size of gamut, I noticed that the volume (3D) or surface (2D) colors (gamut) is more important with a XYZlut profile than Lablut profile.

I also find that the matrix profiles are a little less accurate for correcting delta E 2000, but gives made more smooth (more natural colors) on the pictures.

When the ICC LUT for XYZ and Lab is generated in the same way in DCamProf, but I think the XYZ has a bit larger range before clipping which may be the reason the gamut looks larger. It's the Lab LUT I've concentrated my testing on and testing that it handles strange white balance settings etc, while the XYZ LUT I have just briefly tested that it renders the correct colors in normal conditions. I would not be surprised if the Lab LUT has better behavior for extreme white balance settings than the XYZ LUT, I haven't tested that though.

A matrix-only profile can often be quite accurate for a CC24, but will not be able to match high saturation colors so well. Concerning LUTs DCamProf will per default try to match colors as good as possible (with the natural limits of a 2.5D LUT), and this often leads to a less than smooth profile. To get a smooth LUT profile you generally need to relax it a bit, I've added a few recipes in the basic workflows in the docs.

If you look at a consumer profiler like Adobe's DNG profile editor the LUT it generates doesn't correct lightness at all (-l -1,0 parameter with DCamProf). I think they do it because it's quite difficult to shoot a target without glare and uneven light issues, so correcting lightness for a typical CC24 target shot introduces sharp bends in the LUT without adding much accuracy. It seems like many bundled commercial profiles don't correct lightness either. I'm not 100% sure but I think Hasselblad has only chromaticity correction (hue+saturation) on their bundled profiles, and when looking at the bundled P45+ profile in Capture One it seems to be the same there. Adobe's bundled profiles has some lightness corrections though.

I have not myself really decided if skipping lightness correction in full is a good idea or not for "high end" profiles, but the less sure you are that your CC24 shot is of high quality the more you should consider smoothing lightness or even disabling it all-together.

I suspect that lightness corrections are the most likely to cause problems with gradients, while hue/saturation corrections are less likely to cause problems but I haven't made any deeper research on that yet.

When I make my own profiles I do correct lightness, but I work quite thoroughly with smoothing, looking at plots etc to fix bends where I find them.
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Iliah

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Re: DCamProf - a new camera profiling tool
« Reply #787 on: August 30, 2015, 03:13:38 pm »

yes, a profile with adobe RGB is already well. I will return my ideas when I have a few profiles with SSF method.

Depends, here are some screenshots of a plot of Adobe RGB vs. colours used in household, measured with a spectroradiometer
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AlterEgo

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Re: DCamProf - a new camera profiling tool
« Reply #788 on: August 31, 2015, 01:59:37 am »

just in case it might be of interest/use for somebody or simply for collection ...

I measured my copy (one copy, not multiple samples, sorry) of DataColor SpyderCheckr 24 with i1Pro2 (one device used) using BabelColor, both in XRGA and non XRGA mode, 5 spectral measurements each time... the attached .zip has 2 x 5 and averaged measurements.

this target =


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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #789 on: September 01, 2015, 05:16:05 pm »

The ICC gamut for a camera does not really say much about what real colors the camera actually can capture. A camera is an input device, and you can't see the gamut the same way as for an output device such as a printer or a display.

A ICC Lab LUT will take raw RGB inputs and convert to Lab output, that is 3 values in 3 values out -- a 3D LUT. The LUT needs to cover all combinations of input values (with a limited resolution). As a camera have overlapping color filters it's impossible to get an input signal with say 100% green an 0% red and blue, but that still needs to have some output value in the LUT.

Actually this has been a very hard problem for when designing DCamProf, say 30% of all LUT values are invalid colors and since the calibration makes a model based on real colors and interpolate the rest, the impossible input value combinations get thrown out to crazy positions way outside the human locus, negative lightness and such things. First I just clipped those values, but in practice you then get an "unstable" ICC profile which can lead to strange color effects when you apply an extreme white balance (which may make some of those "impossible" input combinations arise). So I had to fake the impossible values by a special type of interpolation that makes sure that you get sane color output also for insane inputs. It seems like most other profile designers does the same thing in one way or another.

Try pulling the white balance slider to the lowest temperature possible (that will make the whole image blue) and see how the ICC profile behaves. If you have a profile that haven't cared to interpolate outputs the "impossible" inputs, you will probably see colors get clipped to black and possibly get thrown into totally different colors like green, magenta or yellow rather than staying blue.

A LUT can also have XYZ output rather than Lab, but it's not as common so I assume when you refer to XYZ you think about matrix profiles. In this case there's just a simple matrix multiplication that makes the colors, and the matrix has been optimized to produce sane colors in the range it was profiled for, typically a CC24 or similar. It means that for extreme input values you will get crazy output values. The corners of the "gamut triangle" you see in an ICC viewer are 100% green, 100% red and 100% blue, and you can't really reach those points with real inputs, and even if you could the matrix will map those to crazy positions for sure as it has been optimized to make normal colors correct, and that will cause highly saturated colors to get to bad positions.

So in other words, the gamut you see in a camera profile doesn't say anything about the camera's ability to capture colors.
With DCamProf I made a color separation analysis function that can give you some insights into how well the camera can separate colors: http://www.ludd.ltu.se/~torger/dcamprof.html#ssf_csep

It's common to say that "a camera doesn't have a gamut", and sure it does not have a gamut in the same well-defined way as a printer+paper, but it does have limitations concerning color separation. There is no standardized way to define those limits though, and unfortunately you can't get any of that information from the ICC profile.

Of course the ICC profile won't output values outside it's gamut, so you know what values you can't get, but you cannot see which values that represent those "impossible" combinations and thus are meaningless parts of the gamut.


Thanks a lot for these informations.
I made 2 dcp and icc profiles from the ssf D700 and spectral datas of CC24.
With the ICC profile, the gamut is good, in 2D, the behavior seems correct profile for the high and low lights, the 3D shape is regular.

With Lr,  I watched the behavior of these profiles with pictures, visually they are as good as the profile made last week with a semi gloss target with 570 patches without the flare and glare with the shooting. All this remains to be confirmed with measurements (Delta E). (The white balance is ok)

I will continue with CCDigital SG.


« Last Edit: September 01, 2015, 05:33:43 pm by Bip »
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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #790 on: September 01, 2015, 05:21:37 pm »

Depends, here are some screenshots of a plot of Adobe RGB vs. colours used in household, measured with a spectroradiometer



I see some colors outside the gamut Adobe RGB (mesh), is that right must be understood?
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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #791 on: September 01, 2015, 05:28:27 pm »

just in case it might be of interest/use for somebody or simply for collection ...

I measured my copy (one copy, not multiple samples, sorry) of DataColor SpyderCheckr 24 with i1Pro2 (one device used) using BabelColor, both in XRGA and non XRGA mode, 5 spectral measurements each time... the attached .zip has 2 x 5 and averaged measurements.

this target =



Is there a difference between the target CC24 Xrite and Datacolor?
Is what he has one of the best?

(I have not had time to look at the spectral data)

==> I confirm that made a profile with ssf method is easier (if they have the ssf of camera)
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AlterEgo

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Re: DCamProf - a new camera profiling tool
« Reply #792 on: September 01, 2015, 08:12:06 pm »

Is there a difference between the target CC24 Xrite and Datacolor?

some comparison was done time ago = http://www.rmimaging.com/information/SpyderCheckr_Technical_Report.pdf
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Iliah

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Re: DCamProf - a new camera profiling tool
« Reply #793 on: September 01, 2015, 09:46:43 pm »


I see some colors outside the gamut Adobe RGB (mesh), is that right must be understood?

If I understood your question correctly, yes, some colours fall off the AdobeRGB gamut.
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professorbalrog

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Re: DCamProf - a new camera profiling tool
« Reply #794 on: September 03, 2015, 01:32:29 pm »

Hey guys, I am fascinated by this discussion (and pls forgive the crosspost) but I am over my head in trying to get this to compile correctly on OSX. At AlterEgo's suggestion, I'm adding a reply here with my request from this post:

http://forum.luminous-landscape.com/index.php?topic=103561

Quote
Would any of you who are smarter than me using Argyll and DCamProf on a Mac be willing to help me out with it, or point me in the right direction? I'm not at all scared of command-line utilities but I feel like I have no idea how to even get these to compile correctly. I was able to get Argyll to run the scanin command based on the instructions I found here (and after moving the chart reference files to the bin folder):

http://www.trumpetpower.com/photos/Exposure#Normalizing_exposure

But that's about it. DCamProf's instructions say "It should also be relatively easy to build on Mac OS X". I have no idea what to do with that information :/ All I want to do is generate a profile that's roughly as accurate as what the X-rite software can create for use in ACR but one that I can use in Capture One instead (so, ICC right?). I don't need to build a custom target or anything crazy (yet) just the most basic of camera calibrations.

Help? Please?

Again, any help would be HUGELY appreciated, this looks like an awesome and sorely needed tool but I'm not savvy enough to get it running just yet. I suspect I'm not the only one who want's to get their hands on this but can't figure it out.
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Iliah

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Re: DCamProf - a new camera profiling tool
« Reply #795 on: September 03, 2015, 01:49:12 pm »

OS X executable:
http://s3.amazonaws.com/IliahBorg/dcamprof.0.9.4.zip

BTW, in profio.c / dto_u1fixed15 line 1144
if (frac > 0x7FFF) frac = 0x7FFF
This may cause an error.
Maybe to compare with zero?
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torger

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Re: DCamProf - a new camera profiling tool
« Reply #796 on: September 03, 2015, 03:22:38 pm »

I've just released 0.9.5, very minor updates.

Included the fix of the suspicious overflow comparison noted by Iliah. The encoding/decoding of ICC values can be written much more elegant than my quick hack code, may replace it with LCMS2 at some point as was debated early in this thread :).

Anyway the bigger news is that I've completed a tutorial for making a camera profile using DCamProf, it's a separate document found at:
http://www.ludd.ltu.se/~torger/photography/camera-profiling.html

I plan to maintain that like my other photography articles and have it separate from the DCamProf distributition itself.

DCamProf is closing version 1.0. I don't have any pressing features left to implement. The goal was to make a software that would enable me and others to make profiles for general-purpose photography that can work in the same way as bundled profiles (that is work with embedded curves, have some subjective adjustments) in the large well-known raw converters, and I think I've reached that goal now.
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AlterEgo

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Re: DCamProf - a new camera profiling tool
« Reply #797 on: September 03, 2015, 04:14:40 pm »

0.9.5 build for Windows (mingw = dcamprof.exe + libgomp_64-1.dll + both manual AND tutorial / = copies of Torger's web pages and the same converted to PDF /) : https://app.box.com/s/l1ci6j8ybh9t438fnkhlbqwdr9ooxnaq
« Last Edit: September 03, 2015, 04:33:49 pm by AlterEgo »
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Iliah

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Re: DCamProf - a new camera profiling tool
« Reply #798 on: September 03, 2015, 04:36:10 pm »

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Bip

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Re: DCamProf - a new camera profiling tool
« Reply #799 on: September 03, 2015, 05:08:54 pm »

some comparison was done time ago = http://www.rmimaging.com/information/SpyderCheckr_Technical_Report.pdf
I looked at, but it is difficult to do an opinion. I downloaded the spectral datas and, a day, I will try to do a profile.
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