Here are compared the Canon 5D Mark III to its 5D Mark II predecessor at ISO 50 through ISO 25600, whole ISO values.
For this comparison, I reduced my normal sharpening amount from 60 to 40 so as not to accentuate noise too much. As a practical matter, digital images must be sharpened and it makes a better evaluation to process images as similarly to real-world usage as possible, but perhaps not to the full amount of sharpening when very high ISO values are involved. Noise reduction was of course turned off.
Processing was at 5000°K with Tint=0.
Exposure was the same EV value for all, except that ISO 50 was 1/3 stop more exposure in the camera than ISO 100, along with +2/3 stop “push” during RAW conversion. The camera tricked me with its histogram at ISO 50! Both cameras used the same exposure and processing of course.
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