Does a 35mm lens on a Nikon DX camera cause “normal” perspective or distortion?

Question

I use a Nikon D5100 (DX/crop sensor) with the 18–55mm kit lens and I’m considering a fast prime for everyday shooting. From what I’ve read, 35mm is often considered the “normal” focal length on DX, while some people suggest 50mm.

What I’m confused about is distortion. Is distortion mainly caused by focal length itself, or by sensor size? For example, if I mounted a very wide FX lens on a DX camera, would the DX sensor just crop the center of the image while keeping the lens’s optical distortion characteristics?

So with a 35mm lens on DX, do I get a normal field of view without introducing wide-angle/fisheye-like distortion, or does a truly “normal” look depend more on how far I stand from the subject?

user39427 · Accepted Answer

There are two types of distortion:

1) Perspective distortion caused by being too close to your subject

2) Barrel or pincushion distortion caused by the lens optics

35mm and 50mm primes generally have very little distortion in the lens so any distortion you would see would be perspective distortion. You would tend to get more perspective distortion with the 35mm lens because you need to get closer to your subject with the 35mm than you would with a 50mm lens.

If you stand far enough away, both the 35mm and 50mm lenses will give you distortion free images. If you stand too close, both will give you perspective distortion.

This is why 50mm on a crop, and 85mm on a full frame, are often recommended as the minimum lengths for "portrait" lenses.

Does a 35mm lens on a Nikon DX camera cause “normal” perspective or distortion?

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