How could I get an idea of the focal length of the Nikon 50mm f/1.8?
I was thinking of getting the 50mm f/1.8 for my d90. I want to see what kind of view its going to give me. I read that the DX equivelent of the lens is 75mm. Does this mean I just zoom my 18-200 lens to 75 to see what it would look like?
The focal length of a 50mm lens is 50mm'
No, when used on the same camera the focal lenghts of all lenses are directly comparable. The 50mm, when used on a DX camera such as your D90, will work like a 75mm lens would work on a full frame or film camera. On your DX camera however it will work just like any other lens that is set to 50mm. The crop factor comes from the camera body, not from the lens.
So you'd get the same angle of view if you set your available 18-200mm lens to 50mm.
Unless you actually own a full frame or film camera, totally forget about crop factors. They'll only confuse you. Learn what a certain focal length looks like on *your* camera and be done with it. Any other lens with the same focal length will look the same, regardless of whether it is a DX or FX lens.
DX and FX for lenses merely means whether or not they fill the whole frame on full frame/film, it has nothing to do with the crop factor.
@Looney Dufass: Sorry, i accidentally gave you the thumb down as i misread your post at first, and i can't take it back.
As said the focal length is still 50mm, what's more helpful is the angle of view, as zoom lenses often negate the physical dimension of focal length.
So, with a cropped sensor as on a d90 the angle of view of a 50mm lens on the sensor is more like what you would tradtionally expect from a 75mm lens on an 35mm type body. As such, zoom your 18-200 to 50 and, yes, you will have an approximation of the angle of view from a 50mm lens on a cropped sensor.
There are other benefits to a 50 on DSLR, such as control over depth of field, low noise low light photography, bright viewfinder and faster focusing.
Everybody with a compatable body (like the D90) should have a nifty fifty in their kit bag.
Here is a link that will show you the view from various focal length lenses, both on a full frame and APS-C sensored camera.
You can zoom your other lens to give an idea of the field of view (focal length, strictly speaking is the same on every format).
Just make sure you do it with the focal length at infinity because closer focusing distances change the FOV on zoom lenses.
No, 50mm is 50mm, it doesn't matter what camera is being used. You simply zoom your 18-200mm to 50mm to get an idea of the angle of view the lens is going to give.