APS-C on a Sony a7R III

Started Mar 30, 2022 | Discussions thread
Lichtspiel Veteran Member • Posts: 3,725
Re: APS-C on a Sony a7R III

mouseclubhouse wrote:

I have a Sony a7r III, and I have the chance to get a 28-200mm APS-C lens. I know this is a full-frame camera, but I also know an APS-C lens can work on it, but at what cost? Am I correct that it would crop it more (my understanding is that a 200mm would be more like a 300mm?) and would it also negatively affect the quality?

The lens itself would not crop, nor turn into a 300mm, however, you would get heavy vignetting since the lens is not made to cover the entire sensor.

Cropping the resulting image would then be equivalent to using a longer lens (same as with any FF lens though!), how much depends on the FL and the particular lens. At the wide-angle setting, it will vignette more heavily than at 200mm, and you have to crop accordingly .

Of course you can set the camera to APS-C mode, but then you might lose some of the pixel real estate since the camera doesn't know how much it actually needs to cut off and just goes by the 1.5 or 1.6 factor. Since lenses are round (most of them anyway) you can crop (in post processing) heavier on the left and right side while the top and bottom are mostly good.

Besides the need for cropping I don't think it would necessarily affect the quality. This depends more on the particular lens, and lenses made for smaller (denser pixels, say 24MP APS-C)) sensor cameras require higher resolution/better IQ to get the same result as a lens made for a lower density sensor (say 24MP FF).

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