D4 vs 1Dx (Imaging Resource), RAW, ACR, 6400-12800

Started Sep 4, 2012 | Discussions thread
Lance B Forum Pro • Posts: 31,294
Re: D4 vs 1Dx (Imaging Resource), RAW, ACR, 6400-12800

Lance B wrote:

Jack Hogan wrote:

Lance B wrote:

At ISO6400, the D800 is actually ISO4211 and the D4 is actually iSO4388!

A difference of a whopping 0.06 of a stop. Easy to lose perspective when thinking linearly in a logarithmic world, n'est-ce pas?

The difference between an indicated ISO6400 on the camera and an actual of ISO4211 is not .06 of a stop, more like 1/3rd to 1/2 a stop.

Therefore, if you had a camera that was accurate at ISO6400 ...

I believe most cameras 'cheat' more or less the same, see for instance here http://www.dxomark.com/index.php/Publications/DxOMark-Insights/Pushed-ISO-Let-s-make-it-clear/RAW-ISO-measures-are-inferior-to-manufacturer-ISOs-is-this-a-problem

DxO compensates for differences in sensitivity and shutter speed (not aperture?) by plotting its data on normalized curves. Absent those and to help Renato and his comparisons, though, assuming the same Exposure (ss and f ratio) and ISO in both cameras, I think it would be fair to normalize their output by ensuring that the same unclipped highights on both cameras result in the same raw values by playing with EC in the raw converter, before attempting to draw conclusions. The EC that needed to be dialled in would itself give you a value in stops as to the combined error/difference in ss, aperture and ISO of the two cameras.

If on the other hand even Exposure is different, then what are we comparing? Too many uncontrolled variables.

Jack

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