images: A900 vs A99 RAW high ISO comparison

Started Nov 9, 2012 | Discussions thread
philbot Contributing Member • Posts: 846
Re: images: A900 vs A99 RAW high ISO comparison

taamberg wrote:

OK, I am NOT a troll - in fact, I own both an A900 and a brand-spanking new A99. However (well, actually "therefore") I want to make any comparison of these two fine cameras as fair as possible.

The truth is that there IS that semi-translucent mirror that robs light in the A99, affecting exposure. I'm assuming that both the A99 and A900 in your comparison were set to the same aperture and shutter speed, as the A99 came out roughly a third stop darker than the A900

The exposure difference seen has nothing to do with SLT..

Internally, the camera's simulate ISO by applying gains to the sensor signal prior to RAW, any SLT light loss can be taken care of by that mechanism.

It is normal that some camera's have low and some cameras have high ISO gains, leading to what looks to be darker/lighter exposures for the same camera exposure settings..

The A77 confirms this as it produces brighter exposures for the same camera settings then most of it's competition, this is why DPReview/Imaging-Resource who match output exposure levels always give it faster shutter speeds for the same aperture then most camera's, which is exactly the opposite of the A900/A99 scenario.

I agree that ideally you should match output exposure, and as you have done, do it in PP.. doing it by giving the camera's different amount of light (as DPReview and IR do amongst others) is not the right way to do it for ISO comparison.

Don't forget that RAW converters also have some responsibilty in this, the algorithms differ per camera and it's up to each RAW converter to set the overall default exposure from the RAW Data.. so you can get variance there..

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