Olympus OM-D (EM-5) comparison samples are now available.

Started Mar 16, 2012 | Discussions thread
Richard Butler
Richard Butler dpreview Admin • Posts: 2,393
Re: ISO cheating

dr_elis wrote:

E.g. for the ISO 1600 shot OM-D versus G3, aperture f/6.3 for both, now look at the shutter speeds:
Oly 1/400; Pana 1/640

As expected the Oly underrates the ISO setting by more than 1/2 stop. Hence, the real ISO values were roughly Oly ISO 1100, Pana ISO 1600. No wonder the Oly tends to look good.

I wouldn't try to draw conclusions about ISO accuracy from this scene. It is something that we'll look at in the full review.

However, please do not take the DxO 'ISO' figures to mean Olympus is mis-representing ISO - that's not what those figures show.

In effect what they show is how each company (totally legitimately within the ISO standard), chooses to expose their sensors. A lower figure means they're trying to capture more highlights, at the expense of noise - a higher figure suggests they're doing the opposite. It does not mean one is under or over-rating ISO.

ISO as it's marked on cameras is essentially about metering - it defines what shutter speed and aperture are required to give a particular output brightness from a specific scene brightness. That isn't what DxO is measuring, so differences between two figures cannot be used as evidence that either is somehow incorrect.

We will put the G3 and E-M5 alongside one another under controlled conditions to establish the ISO behaviour as part of our review. Until that point, I'm not going to speculate about the results.

Richard - dpreview.com

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