So... I finally come to a decision to go with the OM-D... Is there any big hand users out there?

Started Mar 13, 2013 | Questions thread
Jack Hogan Veteran Member • Posts: 6,942
Issue 2: How to fairly compare output image IQ of two similar DSCs

I never addressed Issue 2 here, but here goes a summary of the posts in the other thread. Given Issue 1, the fact that in-camera ISOs are mostly not directly comparable, how does one then go about comparing two cameras fairly in the same scene and with the same photographic intent (blur, dof, and retained shadows and highlights)? The answer is pretty straight forward.

Place both cameras to look at the same scene, with the same lens, the same Exposure (i.e. shutter speed and f/number) and to record the same tonal range (highlights and shadows). To capture the same tonal range you could simply read the ISO difference in stops off of the DxO graphs and dial in-camera ISOs with that difference into the two cameras. That's how I'd do it, because I trust DxO for things like this. Or you could figure it out yourself as follows:

In Manual mode, set the same shutter speed and f/number in both cameras and place them in the scene. Then take a capture of a gray card with both at the same estimated nominal ISO for the desired tonal range, say 1600. Correct the ISO of one of the two while keeping Exposure fixed, iteratively, until the gray card appears in the same spot of the Raw histogram of both*, say 10% of full scale. This way both cameras will be recording the same range of incoming tones, from shadows to highlights. Having set them up to respond equally to the incoming light, you can now take a capture of the scene with both DSCs, process them with the same Raw converter parameters while ensuring that the brightness and size of the output images are more or less the same and judge their relative IQ - SNR in this discussion - fair and square.

If you were to go through this exercise with the EM5 and the G3, you'd find that you'd end up with the EM5 at in-camera ISO 3200 and the G3 at 1600 - at the same Exposure and very similar SNR (EM5 slightly better as per DxO graph).

The further thing from my mind is suggesting to shoot evey scene in the field like this. But I am suggesting that if you wanted to compare the two cameras fairly that's one way you could do it. On the other hand, comparing two cameras at the same ss, f/n and in-camera ISO setting is more often than not misleading because of Issue 1.

So back to us. Where are my misconceptions and erroneous conclusions here?

* RawDigger is a great free program to obtain a Raw histogram from.

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