CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit

sharky

That image was processed with photoshop and JPG'ed, maybe that's where the artifacts were from. I don't have any DNG's here at the moment, I will upload one this evening for you to look at.

sharky

About the crash troubleshooting:

I have found some more hints in the ROM as to how I should be getting the RAW addresses. Seems I guessed the address exactly right. In some cases though, the RAW buffer will be in yet another place. This is the moment at which it crashes, I think. I will update and test it later today and get you the new DISKBOOT if it fixes something.

igvk

How do you make color profile for this camera to process DNG?
I've read there is an option in Dng4ps2, but it compares RAW and JPG, and AFAIK, it doesn't support 12-bit RAW.

sharky

I don't know much about DNG, but doesn't the DNG itself contain some info on that?

dcraw -v -i shows this:

Filename: RAW.DNG
Timestamp: Sat Jan 17 13:24:12 2009
Camera: Canon DIGITAL IXUS 85 IS DNG
ISO speed: 200
Shutter: 1/64.0 sec
Aperture: f/2.9
Focal Length: 6 mm
Secondary pixels: no
Embedded ICC profile: no
Decodable with dcraw: yes
Thumb size:   128 x 96
Full size:   3720 x 2772
Image size:  3668 x 2756
Output size: 3668 x 2756
Raw colors: 3
Filter pattern: GBRGGBRGGBRGGBRG
Daylight multipliers: 2.656980 1.678213 3.342146
Camera multipliers: 2.656980 1.678213 3.342146 0.000000

Aren't the multipliers what you want ?

sharky

I had a quick look at the source of dng4ps2 and indeed is only does 10-bit as far as I can see.

So no quick fix there ..

igvk

I thought it's closer to "Embedded ICC profile".
But then you need to create and add it in CHDK, I guess.
Actually, I suppose, I need to discover more information on this subject.

igvk

I noticed that there is only "Daylight multipliers" (no "Camera multipliers") string in DNG produced by my camera.
So, this data should be used for color calibration?
And where do you get the values for these parameters from?
Sorry, these could possibly be dumb questions.

sharky

The multipliers are hardcoded in CHDK for this cam. I just copied them from the ixus80.

I have no idea about color profiles, etc ...

igvk

O.K.
As far as I understand, we need someone to make correct color matrices for this camera to build into CHDK (It's different from IXUS 80).

And still, the colors of conversion from DNG will be incorrect and not the same as in JPG.
For this, a DNG color profile is needed (or separate profile, that can be loaded by a RAW conversion program) - and it's a difficult task. Tweaking colors manually for each photo to reproduce natural colors (or jpeg colors) is almost impossible, at least for me.

And that's true for all the cameras with RAW (or DNG) format (for CHDK-enabled RAW there is no support from manufacture or commercial software vendors).

sharky

I found the problem when it crashes

If you half-press the 'shoot' button and let it focus, etc, and then full-press the 'shoot' button everything is OK.

However, if you just press the 'shoot' button fully without waiting for focus, the cam crashes and turns off. Sometimes the screen flashes with some garbage just before crashing.

I'll see if I can figure out what the problem is there.

PhyrePhoX

i think this bug was present on another port as well, i cant remember which cam though - and if it got fixed or at least worked around.

kayec

I took three RAW shots and tried to run show_bad_b.exe against them but it says "File is unknown". I have a 4Gb card formatted at FAT16 with 64bit blocks. Thoughts on why this isn't working?

ewavr

kayec
I took three RAW shots and tried to run show_bad_b.exe against them but it says "File is unknown".

Of course, show_bad_b.exe is outdated, it knows nothing about ixus85.

PhyrePhoX
i think this bug was present on another port as well, i cant remember which cam though - and if it got fixed or at least worked around.

Similar bug is knows as "sporadic RAW images" (RAW not saved if shutter is pressed quickly), it fixed for most cameras.

igvk
And still, the colors of conversion from DNG will be incorrect and not the same as in JPG.
For this, a DNG color profile is needed (or separate profile, that can be loaded by a RAW conversion program) - and it's a difficult task. Tweaking colors manually for each photo to reproduce natural colors (or jpeg colors) is almost impossible, at least for me.

Maybe best solution is conversion 12bit CHDK RAW to 10 bit RAW and using DNG4PS2 for building color profile.

igvk

ewavr
Maybe best solution is conversion 12bit CHDK RAW to 10 bit RAW and using DNG4PS2 for building color profile.

Yes, this way it could be possible to make color matrix (the old way).
Though it won't make the colors correct for all the possible range.

The better solution would be to create DNG color profile for this camera model (a software that understands this format is also needed for conversion).
I saw a discussion on this matter at this forum:
https://chdk.setepontos.com/d/2032

Though, there seems to be no automatic or semi-automatic way (or at least correct for a casual user) to do this yet.

whoever

igvk
Though, there seems to be no automatic or semi-automatic way (or at least correct for a casual user) to do this yet.

No, there's no shortcut. Color profiles are obtained by shooting a calibrated color target in standard lighting conditions, and then calculating the profile with dedicated (possibly homebrew) software. Dave Coffin would normally be happy to help though.

Citing Dave Coffin:
"You'll need a Gretag Macbeth ColorChecker chart. Any professional photographer should have this chart. Wait for a clear, crisp sunny day. At noon, find a place with a clear view of sun and sky. Set the chart in direct sunlight, and photograph it with the lens at the longest focal length (telephoto, not wide-angle)."
"If you shoot the chart indoors, use a D65 lamp on a professional light table. That's what Thomas Knoll used to calibrate the other digital cameras."
(Thomas Knoll is the author and maintainer of Adobe Photoshop and Camera Raw.)

Approximate color transfer matrix could indeed be obtained with DNG4PS2.

igvk

The question is: who will do this for these P&S cameras?

And - some software could be made that does approximately the same thing as dng4ps2, creating profiles by comparing RAW and Jpeg images, though that might be not that accurate.
(I am talking about DNG 1.2 color profiles, not multipliers matrices.)

For now, it seems that each user must do this himself. (Or just use JPG, and that's it.)

P.S. Need to consider buying color chart, monitor calibrator, etc. All for casual photography. 😉 No, I am not a professional photographer! 😀

whoever

Well, Wolf Faust (http://www.colorreference.de/targets/) sells reflective targets for as little as 10 euro -- they are meant for scanners, but can be used with cameras, too.

Then, since camera CCD sensor is a linear device, the (correct) color matrix is quite sufficient for good color reproduction. And if you get Dave Coffin to collaborate, so that the cam gets supported by dcraw, then it'd be a great service to the community, since the whole bunch of image processing software like picasa etc. will eventually pick it up.

Finally, talking about full ICC profiles, there's Timo Autiokari's (aim-dtp.net, under reconstruction at the moment) free profiling software that some people used with success (not me though).

kayec

This all sounds like a lot of work. My understanding is that the point of shooting RAW in the first place is so the camera doesn't have to worry about colour profiles, white balances, temperature, etc. All that is done in post.

ewavr

Well, here is the tool to conversion 12bit CHDK RAW to 10 bit - http://rapidshare.com/files/187706948/12to10.zip.html

I tried to use DNG4PS2 to obtaing color matrix and cropping settings for ixus85 (based on RAW/JPEG pair from igvk):

    // pattern
    #define cam_CFAPattern 0x02010100 // Red  Green  Green  Blue
    // color 0,824186 -0,221391 -0,131676 -0,005513 0,644060 0,039300 0,010558 0,080457 0,221842
    #define CAM_COLORMATRIX1                              \
      824186, 1000000,-221391, 1000000, -131676,  1000000, \
     -5513, 1000000, 644060, 1000000,   39300, 1000000, \
      10558, 1000000, 80457, 1000000,  221842, 1000000
   
    #define cam_CalibrationIlluminant1 1 // Daylight
    // cropping
    #define CAM_JPEG_WIDTH  3648
    #define CAM_JPEG_HEIGHT 2736
    #define CAM_ACTIVE_AREA_X1 6
    #define CAM_ACTIVE_AREA_Y1 12
    #define CAM_ACTIVE_AREA_X2 3690
    #define CAM_ACTIVE_AREA_Y2 2772

Color matrix is not very good for me...

sharky

I'm sorry, are you saying that the color matrix you just posted is NOT good ? Or do you mean that the color matrix currently in my build is not good ? (or both? 😀 )

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