Sony A7R vs Sigma DP3Merrill

Started Feb 11, 2014 | Discussions thread
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Astrophotographer 10 Senior Member • Posts: 7,066
Re: Saving you from "bitter disappointment"
1

Hi Vince,

Yes the A7r images aren't so flash there. It seems mainly from heat haze, you can see it in the cars coming towards you but the cables seem to have the jaggie which is an aliasing artifact. The no AA filter as mentioned is not helping in this example.

The other thing on some the focal lengths are not matched although I think you posted a more comparable focal length. Shorter focal lengths cut through atmospheric distortions.

In the telescope world, atmospheric conditions are callled the "seeing". Its usually different temps of air masses causing bending of light in different ways hence the distortions. Good seeing is a night where the stars are stable and don't twinkle much. It can make a huge difference to a long focal length telescope image and is why they put big telescopes on mountain tops.

Different pixel sizes also come into. Again in telescope world ideally you match the pixel size to the focal length of your telescope and to the local seeing conditions.

In your case here perhaps this is part of what you are seeing. The Sigma most likely has a different pixel size (smaller?) and this better suits the short focal lengths being used.

With longer focal length lenses under the same conditions I would predict that the 2 lenses performance would be closer together.

Greg.

 Astrophotographer 10's gear list:Astrophotographer 10's gear list
Sony Alpha 7R II Sony FE 55mm F1.8 Zeiss Batis 25mm F2 Zeiss Batis 85mm F1.8 Zeiss Loxia 21mm F2.8 +4 more
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