DxOMark's measured ISOs vs. manufacturer ISOs

Started Mar 13, 2013 | Discussions thread
Martin.au Forum Pro • Posts: 13,289
Re: DxOMark's measured ISOs vs. manufacturer ISOs

Mjankor wrote:

Jack Hogan wrote:

Mjankor wrote:

Choose two ISO's that provide a similar 'pleasing tonal balance and brightness', as I stated above.

No, because pleasing brightness can always be achieved (in-camera or in-pp) independently of ISO - but at the expense of noise and highlight clipping. So if you raise the ISO too much you may have an equally pleasingly bright output image but with unwanted clipping. If too little you may have an equally and pleasingly bright output image that's way too noisy. So what do you do?

The answer rests in selecting the in-camera ISO for each camera that results in highlights clipping in the recorded data at the same time. That way you have the same exposure, you record the same scene tonal range and, after you have ensured that both output images are about equally bright, you can finally take a look at them and decide which looks cleaner.

So how do you go about choosing what in-camera ISO results in the same scene tonal range being recorded? You select the in-camera ISO for each camera that results in the same tone from the scene getting recorded at the same level in the Raw data of each.

PS You don't have to do it, DxO does it for us

Ok. You've got the DXO data for my two cameras.

Give me the testing specifications and I'll run a test.

So, you're idea of measuring the difference between the G3 and the OM-D is to:

Set exposure the same.

Set OM-D camera ISO 1 stop higher than G3. 3200, instead of 1600.

In post processing, normalise the two images by shifting the OM-D's image back down about 1 stop or the G3's image up about 1 stop.

Or are you under the impression that they won't need to be normalised?

PS. Your real world, apples to apples results can be achieved (and probably have been achieved) by using 1 stop less exposure on the OM-D, than on the G3 (Actually about 2/3s due to the differences between those cameras you noticed earlier). eg: The OM-D would have used 1/320, the G3 would have used 1:200 (or thereabouts).

Oh, wait a minute. I just spotted you've been using the studio scene from DPR for your example, in which case you cannot expect similar shutter speeds for an equal exposure as the lighting level is not well controlled.

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