New project: camera color profile calculation

ArtDen

Rommel
rommel_a720is_2.zip First is with the original specs, then -1/3 and then -2/3

The matrix is

0.655856, -0.203610, -0.095090,
-0.061367, 0.670395, 0.058562,
0.018814, 0.095240, 0.244112

Not ideal, but...

vit40

ArtDen
Some changes in conditions. Before tacking shot exposure compensation have to be setted to -1/3 or -2/3.
It looks like too bright colors forces camera to apply stronger tone mapping for Jpeg image. Please take another photo with new condition and reupload it again. Sorry for unnecessary work.

True! Especially blue and yellow, with brightest color reaching level 255, are selectively oversaturated. Blown cyan colors are desaturated, preventing ugly cyan look of blown parts of the sky (like on some other cameras, even some DSLR-s) etc etc. I suppose in-camera color conversion uses lookup tables, so it's not possible to entirely emulate it this way, but doesn't matter. In most cases, I prefer my profile for A620, colors are more natural, although jpeg straight from the camera is sometimes more attractive.

dvornik

I think the proper way of exposing the target would be to spot-meter the third grey patch from the bottom right. It's very similar to 18% grey that is usually used for determining exposure.

Here's an a570is picture of an actual mini-target exposed that way. White-balanced for daylight which is technically not exactly correct.

a570is_2.zip - 9.74MB

Reference for why i think that patch is 18% grey:
http://www.rags-int-inc.com/PhotoTechStuff/MacbethTarget/

ArtDen

dvornik a570is_2.zip - 9.74MB

Color is still very saturated there. Try to set exposure compensation to -1

vit40

ArtDen, ther's no need for darker picture than above, as brightest level is barely reaching 210-215

ArtDen

vit40, may be. But matrix calculated from this image gives some inaccuracy in results.

vit40

Can you tell more, maybe I could be of some help ?

fudgey

I don't have any of the DNG tools (nor Windows), so I figured I'd stick the a570is matrix into dcraw. I couldn't figure out if it could be fed to it on command line, but the matrices in the source looked sort of similar, just multiplied by 1e4 and rounded to integers.

dcraw detects the A570IS as A620, so to try out the matrix from this thread

0,594925 -0,168536 -0,076592
-0,345835 1,029958 0,111052
-0,045052 0,156228 0,349470

I replaced this in dcraw.c

{ "Canon PowerShot A620", 0, /* DJC */
{ 15265,-6193,-1558,-4125,12116,2010,-888,1639,5220 } },

by this:

{ "Canon PowerShot A620", 0, /* ArtDen/dvornik A570IS */
{ 5949,-1685,-766,-3458,10300,1111,-450,1562,3495 } },

and tried 'dcraw -W' for a few CRW files comparing the regular dcraw, modified dcraw and the Canon JPG. I suppose I guessed correctly as the images from the modified dcraw are a lot better (=closer to the JPEGs) than from original dcraw with the A620 matrix.

They still are quite noticeably off in color (and brightness as well I suppose), though.

ArtDen

vit40
Can you tell more, maybe I could be of some help ?

I don't have any idea why is this error occurred when program calculates matrix. Someone tries to create same software concurrent with me. May be he can create better algorithm. Anyway I will try to improve my algorithm later.

ArtDen

fudgey
I don't have any of the DNG tools (nor Windows), so I figured I'd stick the a570is matrix into dcraw. I couldn't figure out if it could be fed to it on command line, but the matrices in the source looked sort of similar, just multiplied by 1e4 and rounded to integers.

I uploaded setup of dng4ps2 software with new matrices here: http://dng4ps2.homeftp.org/dng4ps2-0.2.2matrix.exe so you can use other RAW converter (not only dcraw) for developing your photos.

Btw, can you upload one or two images (RAW and Jpeg files) from A570. I need it to check my results

nikopol

This one made with A710 (My Colors neutral, -2/3 EV):

http://www.zshare.net/download/7004753d43ccbf/

ArtDen

nikopol
This one made with A710 (My Colors neutral, -2/3 EV):
http://www.zshare.net/download/7004753d43ccbf/

nikopol, did you test other color profile for A710? Does it show good result?

vit40

ArtDen
I uploaded setup of dng4ps2 software with new matrices here: http://dng4ps2.homeftp.org/dng4ps2-0.2.2matrix.exe so you can use other RAW converter (not only dcraw) for developing your photos.

Hm ... is there a simple way to change the color matrix in DNG4PS-2 (other than reconpiling the program)? Current version doesn't use header files at all, everything is hardcoded in the program

ArtDen

vit40Hm ... is there a simple way to change the color matrix in DNG4PS-2 (other than reconpiling the program)? Current version doesn't use header files at all, everything is hardcoded in the program

May be I will do ability to configure matrices for DNG4PS2

ke7doy

I have tested the program given at the link for the A570IS. This solution seems to work verry well! Thank You!

dvornik

ArtDen
Btw, can you upload one or two images (RAW and Jpeg files) from A570. I need it to check my results

If you still need them here are two daylight images
img.zip - 20.49MB
and one flash image
img2.zip - 7.45MB

whoever

Here's a couple of test shots with IXUS 950 (SD 850) 1.00C, ixus950_sd850_raw_test.rar - 16.07MB. I reckon it should have the same profile as A720 and S5 IS. Physically the same sensor, right?

ArtDen

whoever
Here's a couple of test shots with IXUS 950 (SD 850) 1.00C, ixus950_sd850_raw_test.rar - 16.07MB. I reckon it should have the same profile as A720 and S5 IS. Physically the same sensor, right?

Thanks for images! I calculated color matrix, inserted your camera model into DNG4PS2 and reuploaded it here: http://dng4ps2.homeftp.org/dng4ps2-0.2.2matrix.exe. You can test

whoever

Thanks ArtDen, looks better than everything I tried before. Would you post the matrix, so that I can play with it, compile dcraw? And -- is it really different from what you find for A720 ans S5 ?

ArtDen

whoever
Would you post the matrix, so that I can play with it, compile dcraw?

Matrix is in first post of this thread.

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