D90 30mm vs 50mm

[Alex Ristea]

So I know a little bit about sensor size, in the sense that I know that my D90 isn't a full frame sensor. I've heard some people say that taking the crop into account, a 30mm is pretty much the same as a 50mm.

What is the difference? I have a 50mm prime lens now, and I'm wondering if the focal length is longer than what it should be. Should I have gotten a 30mm instead?

[inkista]

If the 50's working for you, than I don't think there's a problem. It's only if you feel that the 50 is too long and frames too tightly, that you might be happier with the 30.

This kind of "focal length equivalence" only really has meaning if you shot a lot of film or full frame, so that you mentally translate a given focal length to a given field of view. It's just a way of adjusting that mental translation.

[OsmosisStudios]

Focal length equivalence also doesnt take distortion, perspective and bokeh into account either.