Sony NEX Camera + E-Mount Lens = Crop Factor???

Started May 2, 2013 | Questions thread
RGBaker Contributing Member • Posts: 962
Re: Sony NEX Camera + E-Mount Lens = Crop Factor???

GaryR60 wrote:

Correct. What I wonder, though, is what the effect is when using a legacy lens made for use on a 35mm SLR? Since the back of the lens is not cropped, like the NEX native lenses are, but round, instead, how does this affect the image size, or does it?

The fact that the legacy lens can make an image circle large enough to cover a FF sensor is irrelevant if you are using a crop sensor.  The focal length of a lens determines the angle of view in cooperation with the imaging sensor size -- so a 50mm lens is always a 50mm lens, but the angle of view is wider if you use it on a FF sensor, and narrower if you use it on an APS-C sensor as the 'excess' is cropped out.  If you take a lens built for APS-C, it will have whatever focal length it was designed with, but the image circle will not cover the entire sensor so you will have some radical vignetting as part of your image.
Those that have used formats other than 35mm film in the past -- 2 1/4 square, 6x7, 4x5 -- or those that have worked with a lens on an enlarger have long known this reality.  Many crop camera users are learning it for the first time ...
Cheers,
GB

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