Do you remember Mason Resnick from Popular Photography? I do. I enjoyed his articles in PopPhoto for years.

Mason is now an Editor for Adorama Learning Center and he has conducted a full-frame DSLRs research taking in the lab all 6 modern DSLRs: Canon 1Ds Mark III, Canon 5D Mark II, Nikon D3X, Nikon D3, Nikon D700 and Sony Alpha 900. According to his findings, all full framers have inaccurate ISO settings!

In a nutshell, the actual ISO measurements results vs. “official” ISO setting for the full-framers look as follow:

Model Actual ISO ISO values ‘Manufacturer’->’Measured’
Canon 1Ds MK III consistently at around half a stop lower than the indicated speed 100->73, 200->144, 400->285, 800->578, 1600->1171, 3200-2166
Canon 5D MK II 1/4-1/3 less than reported by Canon 100->73, 200->143, 400->285, 800->564 and the highest 25,600->15,110 only!
Nikon D3X I was amazed to learn that ISO 50 in D3X is not a real thing! It seems to be an in camera post processing for ISO 100 (both 50 & 100 were measured as ISO 78)! ISO 200 to 1600: 1/4 less than reported by Nikon; ISO 3200-6400 – 1/3 underexposure 50->78, 100->78, 200-170, 400->337, 800->674, 1600->1369
Nikon D3 consistent 1/3 underexposure 200->161, 400->326, 800->635, 25,600->15,134
Nikon D700 consistent 1/3 underexposure, not including high ISO 200->162, 400->327, 800->651, 1600->1277, 25,000->14,085 only
Sony Alpha 900 consistent 1/3 underexposure, excluding ISO 100->119 – a 1/5 stop overexposure! 200->151, 400->303, etc with 30% less

Want to review ISO measurement results for APS-C sized DSLRs like EOS 50D/40D/30D/20D, Nikon D90/D300/D200 and others?
Read this article by Mason Resnick

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