Massive Mirrorless Camera ISO Signal/Noise Shootout

Started Aug 15, 2010 | Discussions thread
Amin Sabet
Amin Sabet Veteran Member • Posts: 6,781
Re: Massive Mirrorless Camera ISO Signal/Noise Shootout

panamamike wrote:

Why do I say it's not fair? If you look at the DXOMark site, you'll see the NEX-5 true ISO ratings are closer to 3/4 of a stop lower than the Sony indicated stop, for example ISO 200 is actually closer to ISO 130. On the other end the of the spectrum, the GH1 ISO ratings are about a quarter stop higher. That is at ISO 100 the GH1 is more along the lines of ISO 130.

It's a little unfair, but unfair to the Sony not the GH1. In comparing processed files of similar brightness at nominal ISO 200, the Sony is shooting at ISO 130 (per the DxOmark definition of ISO) and those files are being "pushed" to ISO 200-equivalent brightness during RAW conversion, while the Panasonic files are being shot at ISO 270 (per the DxOmark definition of ISO) and being "pulled" down to ISO 200-equivalent brightness during RAW conversion. Remember that these sensors are being given the same amount of light (same f-number and shutter speed) for any given nominal ISO, so the camera which uses more analog gain rather than digital gain (pushing) to arrive at a matched final apparent exposure is at an advantage in a noise contest.

Also, how did they get GH1 at ISO 6400?

That was explained in the test methods. Cameras without native ISO 6400 settings were shot at ISO 3200 underexposed by a stop and pushed a stop during processing.

Using DxOmark terms of ISO for the nominal ISO 6400 shootout, the GH1 is being shot at DxOmark-measured ISO 4200 (nominal ISO 3200) and pushed to ISO 6400-equivalent brightness while being given the same amount of light (f/5, 1/30s) as the NEX5 being shot at DxOmark-measured ISO 4300 (nominal ISO 6400) and pushed to ISO 6400-equivalent brightness. Couldn't be much more fair than that.

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Amin

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