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Subject: Re: ACR Calibration

At least the green patch values were obtained as you suggested, Peter. Hopefully, I did things correctly the first go 'round.

But I just went out and took a few shots of my color checker in some late afternoon (4PM PST) moderately overcast conditions. White balance was 6250K with Tint of -4. Bruce's kind of day! Exposure info as follows: 1/125 at f5.6, focal length 55 mm, ISO 200. Had to bump exposure +.3 in ACR (+1/3 on camera over exposed white patch to 251) and drop exposure to +24. Everything else at defaults.

Perhaps not surprisingly, the patches come out within a level or two of the strobe values I posted earlier. This is true for both absolute values and relative values, as well. I also tried several different exposures (all overexposed and then brought down in ACR)and found little difference as I had before.

Given the drudgingly similar light in the Bay Area and the Oregon Coast I think we might conclude that the light source is not to blame, especially given that my checker shot outdoors in daylight and indoors with strobes produce virtually identical values. There certainly appear to be some significant differences between our 300D's unrelated to light source.

I guess we deviated from your original suggestion, Peter but I think we may have a valid comparison of two cameras nonetheless.

Any other Rebels out there care to weigh in?


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