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Subject: Re: ACR Calibration



Ok, the results are in. Unfortunately we are only comparing two cameras but clearly there are some significant differences (and a couple of notable similarities) between our two 300D's. Values to the far right are exposure adjustments needed to bring the "primary" color value to the ProPhoto target value (Lindbloom values). Settings used in ACR 3.3 are as Peter suggested earlier.

CRW_0728.dng Bruce
WB 6100/-6 Daylight
Red = 123 60 49 exp. +0.3
Light Skin = 161 140 122 exp. +0.35
Green = 80 123 64 exp. +0.40
Yellow Green = 142 167 73 exp. +0.40
Blue = 50 41 126 exp. +0.60
Blue Sky = 90 99 134 exp. +0.35

CRW_3874.crw Les
WB 6300/-3 Daylight
Red = 122 58 48 exp. -0.35
Light Skin = 161 134 121 exp. -0.35
Green = 84 123 73 exp. -0.25
Yellow Green = 143 169 78 exp. -0.20
Blue = 54 49 125 exp. 0.00
Blue Sky = 91 99 133 exp. -0.25

Bruce and I have also compared calibration values for these respective files and they are quite different indeed. I even ran the Fors script on Bruce's file and duplicated his results as a check(save for an apparent typo).

Unfortunately, the sample size is too small to say we've proven anything from a scientific standpoint but it should be enough to suggest we assume there is significant camera to camera variation for the Canon 300D until proven otherwise. FWIW, I've also tried different camera exposures and seem to come up with the same results each time.

Thanks for helping with this exercise, Bruce!

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