Gamma Correction - RAW Shooting and Processing - CHDK Forum supplierdeeply

Gamma Correction

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Gamma Correction
« on: 26 / January / 2009, 18:34:43 »
I have never used CHDK before and am totally new to this.

I had an A75 which mercifully croaked so I replaced it with an A590 IS. Last night I took my first picture with the A590 and it has the same problem my A75 had: there is no detail in the darks. It is as if the darkest areas are being compressed to black or very near to it. Shaded/dark gray areas are just too dark. I do have extensive experience with professional video cameras and it looks to me as if this is a gamma issue. I have used QuickGamma to calibrate my LCD monitor so I'm confident the problem is not with my display. If I view my display at a radical angle (from above), the darks come up and it looks much more like what I would expect, so the information is there.

Here is a sample picture taken with my A75. I've viewed this picture on two different displays and the tree behind the bicyclists just looks black. No shading, no gradation, just black (the A590 IS is no better):

My question is, is there a simple/straightforward way of using CHDK to modify the transfer curve inside the camera, or am I better off downloading the pictures and applying gamma correction with external software? If it has to be done outside the camera, I would like to apply a global gamma correction value in batch mode to all pictures rather than process each one individually, but be able to fine tune individual pictures later on as needed.
« Last Edit: 26 / January / 2009, 18:41:58 by chris319 »


Offline whim

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Re: Gamma Correction
« Reply #1 on: 27 / January / 2009, 04:20:34 »


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