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

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Offline PhyrePhoX

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #70 on: 21 / January / 2009, 16:01:34 »
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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.

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Offline kayec

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #71 on: 21 / January / 2009, 16:27:09 »
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?

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Offline ewavr

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #72 on: 21 / January / 2009, 20:19:03 »
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Of course, show_bad_b.exe is outdated, it knows nothing about ixus85.

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.

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.

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Offline igvk

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #73 on: 22 / January / 2009, 01:12:02 »
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:
http://chdk.setepontos.com/index.php/topic,2032.0.html

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


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Offline whoever

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #74 on: 22 / January / 2009, 03:37:54 »
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.

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Offline igvk

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #75 on: 22 / January / 2009, 04:19:23 »
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! :)

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Offline whoever

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #76 on: 22 / January / 2009, 04:54:30 »
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).
« Last Edit: 22 / January / 2009, 04:56:15 by whoever »

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Offline kayec

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #77 on: 22 / January / 2009, 10:50:46 »
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.



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Offline ewavr

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Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #78 on: 22 / January / 2009, 12:17:10 »
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):
Code: [Select]
    // 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...

Re: CHDK for PowerShot SD770 IS/DIGITAL IXUS 85 IS: Update: Pg2 RAW in 12bit
« Reply #79 on: 22 / January / 2009, 12:26:57 »
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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