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SX200IS - Problem with red color in DNG

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Offline aepl

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SX200IS - Problem with red color in DNG
« on: 25 / January / 2011, 04:19:20 »
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I have a Powershot Sx200is and I shoot DNG.

I found a problem with the red color when I process the DNG file with ACR (If I process it with RawTherapee there is not problem). The problem is that the red color looks like magenta when I shoot without flash. Do I need to calibrate the camera in ACR? How do I do these task?

The link por the DNG file is http://www.megaupload.com/?d=T2M79Z2L and the link por the JPG file is http://www.megaupload.com/?d=FDGXI978.

I apologize for my english.

Thanks in advance.
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Offline vit40

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Re: SX200IS - Problem with red color in DNG
« Reply #1 on: 25 / January / 2011, 11:04:32 »
Take a look at the topic about my dng profile generator project

http://chdk.setepontos.com/index.php?topic=5709.0

If you would like to have a correct profile and you think the whole procedure isn't too complicated for you, drop a note in this or that topic, or send me a PM.
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Offline aepl

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Re: SX200IS - Problem with red color in DNG
« Reply #2 on: 25 / January / 2011, 13:30:55 »
I will read the topic you suggest me and I will contact you.

Thanks a lot for your response.
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Offline aepl

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Re: SX200IS - Problem with red color in DNG
« Reply #3 on: 29 / January / 2011, 11:27:32 »
@Vit40.
I uploaded two files to http://www.megaupload.com/?d=SWJZZSVW
I think they are ok to do a profile for the Powershot SX200IS camera.
Thank you very much for your help.
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Offline vit40

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Re: SX200IS - Problem with red color in DNG
« Reply #4 on: 29 / January / 2011, 13:29:11 »
hi,

I got the pictures and they are ok, but there is a problem - jpeg processing in this camera corrects geometrical distorsions and vigneting of the lens - obviously a new feature of Digic IV processor (cameras I calibrated so far had Digic II or Digic III). So, jpeg developped by the camera doesn't match the raw geometrically and corners are brightened. Because of that, my program would give useless results

I downloaded the manual, but I can't find an option in menu to turn this feature off. For instance, EOS 550D has this option and it is called Lens Peripheral illumination correction. So, calibration won't be possible this way, unless someone add this option to CHDK

The best you can do at the moment is to use Camera Calibration pane in ACR and move slider Red Primary hue to the right. After some playing with this slider on your picture, correct position is somewhere between +25 and +30. That will correct magenta cast in red colors (like on OldSpice). Other colors seem to be more-or less ok. However, it is not possible to match the camera rendering using a 3x3 matrix profile, embeded in a dng - that's why I made this program, but you can still get quite good colors this way

Vit

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Offline aepl

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Re: SX200IS - Problem with red color in DNG
« Reply #5 on: 30 / January / 2011, 06:22:35 »
I appreciate your help. I will try your advices.
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Offline quid

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Re: SX200IS - Problem with red color in DNG
« Reply #6 on: 30 / January / 2011, 08:48:02 »
You can check if distortions and vignetting are still visible on maximal zoom. On my SX130, which also has a 12x zoom, I see heavy corrections made on wide angle, but can't see any on tele.
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Offline vit40

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Re: SX200IS - Problem with red color in DNG
« Reply #7 on: 30 / January / 2011, 09:13:18 »
Here is a test image, based on files aepl sent me, so you or aepl (or someone else) can try to develop it with various zoom position and see what happens. Maybe result will be ok (depending where is this additional processing in the workflow of the camera), although I think there is little posiibility for this to happen

http://www.megaupload.com/?d=6KGYPVAT

Calibration will work only if the chart on developed image is undistorted (square) and gray area around chart has the same brightness (RGB value) in corners and between the corners. However, if result turned to be ok, I need aepl to develop this image, because it must be developped with the same WB as original files

Edit: another thing - SX200 has an option named i-Contrast, which works like Fill-in slider in ACR. Set it to OFF in the shooting menu

« Last Edit: 30 / January / 2011, 09:23:28 by vit40 »
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Offline quid

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Re: SX200IS - Problem with red color in DNG
« Reply #8 on: 30 / January / 2011, 10:16:24 »
Both images were developed on full zoom, with iContrast off and on Custom Color. IMG_1151.JPG with Sharpness in middle setting, IMG_1152.JPG with Sharpness in lowest setting.

http://www.megaupload.com/?d=4KKOM838

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Offline vit40

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Re: SX200IS - Problem with red color in DNG
« Reply #9 on: 30 / January / 2011, 10:48:48 »
Woooow, it looks very promissing. Image is slightly offset, because crop area of this sensor is whether slightly different on SX130 than on SX200, whether parameters written in a DNG file are slightly wrong, but I can realign it in a photoshop, as whole chart is inside jpeg.

However, I can't use this image because it has wrong white balace. So we have two possibilities

1) aepl, if you are still reading this topic, try developping crw file I attached in the previous post. Use maximal zoom and turn i-Contrast OFF in the menu.

2) otherwise, quid, you can send me a new dng+jpg pair according to first part of the procedure and I'll generate a new crw file according to your manual WB setting

Since both SX130 and SX200 seems to have the same sensor, profile should be good for both
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