a57 v d5100 for first DSLR

Started Apr 6, 2013 | Questions thread
Bjorn_L Veteran Member • Posts: 5,770
Re: a57 v d5100 for first DSLR

Fat Dragon wrote:

Wally626 wrote:

Sony in the metering system takes into account the 1/2 stop light loss from the mirror. The only way to do this is to adjust the ISO values. So if you have a scene that would require a 1/100 second exposure at f/8 and ISO 800 on the Nikon inputing the same exposure values will also result in a good image on the Sony. Sony cannot play with the shutter speed or aperture and stay consistent with the world of other cameras so they change the ISO values. The adjustment is at most 1/2 stop so if the Nikon is using ISO 1600 the Sony would be using a real-life ISO 2263. This is why the Sports (ISO) rating is about 1/2 stop lower. In practice 1/2 stop usually has little effect, but the Nikon would come out a little ahead in single frame low light shooting.

Is this claim based on your own observations or is it verifiable by some means?

You can see the results measured in RAW ISO performance at DXOMark.com if you want to know some of what is going on in there.

The a57 gives up 1/3 to 1/2 stop in ISO as well as a trivial amount of DR and color sensitivity due to their use of the old translucent mirror tech.


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