Hi,
I described the procedure briefly when you contacted me last week (I was in a hurry), so I'll try to be more descriptive this time
First, I need a dng from the camera and corresponding jpeg just to get some exif information (camera name, model, size and position of jpeg, white balance, color matrix), so it's not very important what's in the photo. Here is what you should do:
1) in CHDK menu, select RAW parameters, then option "DNG format" and "DNG file extension"
2) in factory menu of the camera, set jpeg size to large
3) for the start, I suggest that you simply choose ordinary daylight scene, like a shot through the window on ordinary sunny day, avoiding too many shadows, cloudy/rainy/foggy weather, so that camera will measure a color temperature around 5000 K and I can check that white balance of color matrix, embedded in a dng, is aproximately ok. Content of this picture is not important for calibration process
4) switch white balance to manual (last option in WB menu). Set manual white balance by pressing menu or disp key (depending on the camera model). You can use gray card or a sheet of white paper here, but I think it would be ok if you just point a camera to the scene and press menu / disp. Don't use Daylight white balance or something else - must be Manual
5) take a photo using that manual white balance. You must not set different manual white balance (by pressing disp/menu key in manual WB again) until you develop raw image that I will send you, but you can freely use the camera with any WB settings (auto, daylight etc) in the meantime - just don't recalibrate manual WB in the meantime
6) upload a dng and jpeg somewhere where I can download it. Use zip or rar, so that file is smaller. Don't change any information in a dng with some external program like exiftool, just leave it as it is
7) I'll check exif informations in a dng, generate a crw file and send it to you
8 ) You will upload crw to SD card - card reader is needed
9) If camera has custom color mode (like A650, SX110), select custom color, move sharpening to lowest position. You can leave contrast and saturation in the middle position or choose some other position if you are using it, but I suggest leaving it in the middle for the beginning. If camera doesn't have that mode (like A620), use low sharpening mode. If there is no low sharpening mode, just leave on normal / effect off mode
10) select ISO 400 to decrease in-camera sharpening further (to minimise calibration error because of sharpening effects)
11) check that jpeg size is still on large. Also, select superfine jpeg quality this time
12) select manual exposure, 1/500s or something similar. Aperture is not important. Make sure flash is deactivated / closed
13) set WB to manual (if you changed to something else in the meantime), BUT don't press disp or menu again - you must use the same manual WB as first time, because test crw file will be generated according to that white balance; otherwise we will have to repeat the procedure
14) in CHDK menu, select RAW parameters, then RAW develop. Browse to the name of crw file that you uploaded to SD, press set. You will get a message to switch to record mode and take a shot
15) exit chdk menu, press the shutter. On LCD, you will see a test image with many different colors, developed from crw
16) send me that jpeg
17) if everything goes well, I will generate a profile and post it
I hope it's not too complicated
As I said, this profile will be usable only with latest ACR or Lightroom versions, so it will be useless with other programs that don't use dng profiles or very old ACR versions that didn't support dng profiles
Vit
Additional note: this calibration procedure probably won't be possible for some cameras with Digic IV (V, VI ...) processor, because Digic IV corrects vigneting and geometrical distorsions of the lens when developping jpeg. However, it worked on SX 200 IS and SX 130 IS, with these additional settings for the second part of the procedure
- zoom at tele position (no lens correction at that position for these cameras)
- i-Contrast OFF
- ISO set to 200 (because of blur applied by SX130 at ISO 400; this wasn't an issue in SX200)
