DxOMark's measured ISOs vs. manufacturer ISOs

Started Mar 13, 2013 | Discussions thread
Jack Hogan Veteran Member • Posts: 6,988
The Heart of the Matter

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 fairly 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 of full scale in the Raw data of each.

PS You don't have to do it, DxO does it for us. And DxO tells us that to record the same tonal information from the same scene for a given exposure and equally bright and balanced outputs, the EM5 should be set to ISO 3200 and the G3 to ISO 1600. And then you look at the real world apples-to-apples results

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