Confusion on Crop Factor

[jpschlosser]

Originally Posted by OsmosisStudios

[...]
Practically, all you need to know is whether your camera is FX or DX. Your D5000 is DX, so any focal length (ANY!) you see has to be multiplied by x1.5 to give you the equivalent field of view. This is really only of value if youre comparing shots from a DX camera and an FX camera using different lens.

So does this mean that if I get a 35mm for my D5000, it will be roughly the equivalent of a 50mm on a full frame?

I'm trying to decide whether I should get a 35mm or a 50mm. If a 35mm will be roughly equivalent to a 50, I'd rather get the 35 at half the price, since apparently the only AF-S 50mm lens for a D5000 costs around $500, which is out of my budget right now.

Still learning the ropes...

Thanks!!

[dcclark]

Originally Posted by jpschlosser

So does this mean that if I get a 35mm for my D5000, it will be roughly the equivalent of a 50mm on a full frame?

I'm trying to decide whether I should get a 35mm or a 50mm. If a 35mm will be roughly equivalent to a 50, I'd rather get the 35 at half the price, since apparently the only AF-S 50mm lens for a D5000 costs around $500, which is out of my budget right now.

Still learning the ropes...

Thanks!!

Correct. 35 x 1.5 = 52.5, so it's about the same as a 50mm. The new 35mm f/1.8 is excellent by all accounts.

[jpschlosser]

Thanks, I'll use my 18-55mm at 35 and 50 to see which I like better to help my decision in buying a prime.

Once I decide that, it will be between a 35 or 50 and a 55-200 zoom... decisions, decisions.

[jpschlosser]

Originally Posted by dcclark

Correct. 35 x 1.5 = 52.5, so it's about the same as a 50mm. The new 35mm f/1.8 is excellent by all accounts.

Follow-up question: the 35mm I'm looking at says it's "DX". Does that make a difference? I.E. is this lens designed for the DX sensor, and so it's an actual 35mm, and not a 50mm equivalent?

Thanks a lot.

[OsmosisStudios]

DX just means that the lens is designed to only cover the DX sensor size. If used on an FX or film camera it would have dark/black corners.

[vandergus]

Originally Posted by jpschlosser

Follow-up question: the 35mm I'm looking at says it's "DX". Does that make a difference? I.E. is this lens designed for the DX sensor, and so it's an actual 35mm, and not a 50mm equivalent?

Thanks a lot.

Osmosis, this is why we bother correcting statements like this.

jp, focal length is a property of the lens (not a measure of the field of view) and will not change regardless of what camera the lens is mounted on. Field of view is determined by the combination of the focal length of the lens and the size of the sensor/film of the camera. So a 35mm DX lens and a 35mm FX lens will have the same field of view when mounted on a DX camera.

[Almond.Butterscotch]

Originally Posted by vandergus

Osmosis, this is why we bother correcting statements like this.

Actually, this is exactly the reason why I said what I said in the other thread. It's a confusing topic to those of us who've only ever had limited experience with film.

[ARMONDJG]

I think the best thing is to stick to plain english. Crop is selecting a portion of the photo- basically you are "cutting out" a part to keep and a there remains a part to discard. Magnification "enlarges" an object - crop does not "magnify". Think as "crop" in terms of "angle of vision" -something like blinders on a horse. Spread open the blinders - the horse sees more from left to right. Force the blinders closer together and the horse sees less of the panorama from left to right. There is no magnification because of the blinders nor their position -open or closed.

[OsmosisStudios]

Originally Posted by ARMONDJG

I think the best thing is to stick to plain english. Crop is selecting a portion of the photo- basically you are "cutting out" a part to keep and a there remains a part to discard. Magnification "enlarges" an object - crop does not "magnify". Think as "crop" in terms of "angle of vision" -something like blinders on a horse. Spread open the blinders - the horse sees more from left to right. Force the blinders closer together and the horse sees less of the panorama from left to right. There is no magnification because of the blinders nor their position -open or closed.

Very true, hence the term "crop factor". However, the cropping that is being done alters, as you say, the field of view. In practical terms, FoV and focal length are intrinsically connected. Thus sprang the idea of a crop factor multiplying your focal length.