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Forum: Photographic Technique
10-28-2007, 07:50 AM
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I posted some to that origianl discussion. My approach to determining if there is an impact is to measure the tone curve of the RAW image and compare the tone curves under various conditions.
I originally did this with a VBA program in Excel. But it had a number of problems. I just recently re-wrote the tone curve program in Java. It produces three curves (one for each color) of the average raw values in a list of files. I use it by taking "white wall" images of a "pure" white piece of Epson Matte hea vyweight paper. I vary the exposure in steps of 1/2 stop from well below black to well above saturation.
From the curves I can tell a number of important things. Most important to me is how many stops from meter reading to saturation for various conditions.
I have only completed one sequence of white wall shots (for incadescent light at 6.8 LV).
Next step is to vary the WB settings (used AWB) and then do a custom WB to see if there are any changes to the curves.
Here is my first curve:
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