Full frame lens - Whassat then?

[james_tigerwoods]

I've been reading up on lenses as I really, really want to buy a new lens - possibly one of these two:

http://www.parkcameras.com/11193/Nikon-AF-S-DX-NIK... 35mm for £169 or

http://www.parkcameras.com/10061/Nikon-AF-S-50mm-f... 50mm for £279

However, when talking about lenses, I'm asked if I want a "Full frame lens" - what, exactly, is a full frame lens?

[SamHH]

The first digital SLR cameras were basically a 35mm SLR film camera with a digital sensor stuck on the back. They've got more sophisticated since then, but they still share the same basic design with 35mm film cameras.

However, the sensor in most digital SLRs is smaller than a frame of 35mm film. If I remember, yours is a Nikon D40, and this has a small sensor. In having a smaller sensor, these cameras don't require such a large circle of light to be projected onto the sesnor, and therefore the lens can be smaller and lighter than would be required for a 35mm film camera. Manufactures make lenses specially for these small-sensor cameras and distinguish these lenses with a label like DX (Nikon) or EF-S (Canon). If you use one of these lenses on a 35mm film SLR, or a top-of-the-range digital SLR that has a 'full frame' sensor (i.e. the same size as a full frame of 35mm film) the corners of the photo will be black. Therefore, a full frame lens is one that is compatible with a camera with a full-frame sensor or 35mm film. The other way round, you don't have to worry about it: any lens with the correct fitting is compatible with a small sensor camera.

Edited by SamHH on Tuesday 15th September 22:18

[diesel head]

If you have Nikon D40 you also need to be careful about lenses, as in order to make these camera's cheaper they omitted the autofocus lens from the camera, meaning that any lens you buy will need an auto focus motor in it.

[james_tigerwoods]

SamHH said:

The first digital SLR cameras were basically a 35mm SLR film camera with a digital sensor stuck on the back. They've got more sophisticated since then, but they still share the same basic design with 35mm film cameras.

However, the sensor in most digital SLRs is smaller than a frame of 35mm film. If I remember, yours is a Nikon D40, and this has a small sensor. In having a smaller sensor, these cameras don't require such a large circle of light to be projected onto the sesnor, and therefore the lens can be smaller and lighter than would be required for a 35mm film camera. Manufactures make lenses specially for these small-sensor cameras and distinguish these lenses with a label like DX (Nikon) or EF-S (Canon). If you use one of these lenses on a 35mm film SLR, or a top-of-the-range digital SLR that has a 'full frame' sensor (i.e. the same size as a full frame of 35mm film) the corners of the photo will be black. Therefore, a full frame lens is one that is compatible with a camera with a full-frame sensor or 35mm film. The other way round, you don't have to worry about it: any lens with the correct fitting is compatible with a small sensor camera.

Edited by SamHH on Tuesday 15th September 22:18

Thanks - that makes sense, I think.

And yes, I do have a D40

[james_tigerwoods]

diesel head said:

If you have Nikon D40 you also need to be careful about lenses, as in order to make these camera's cheaper they omitted the autofocus lens from the camera, meaning that any lens you buy will need an auto focus motor in it.

Thanks - This much I know and I have to be looking for AF-S lenses....

[Simpo Two]

There's another advantage when using 'full-frame' (FX in Nikon-speak) lenses - on the smaller DX sensor there should be no vignetting whatsoever - all the cruddy corners are chopped clean off

[GetCarter]

...and one other point: When you put a 50 mm lens on a D40 it 'effectively beecomes' a 75mm lens. Put the same lens on a Full frame camera like the D3 and it's back to 50mm.

[james_tigerwoods]

GetCarter said:

...and one other point: When you put a 50 mm lens on a D40 it 'effectively beecomes' a 75mm lens. Put the same lens on a Full frame camera like the D3 and it's back to 50mm.

[idiot mode]

Why?

[/idiot mode]

[Nick M]

james_tigerwoods said:

GetCarter said:

...and one other point: When you put a 50 mm lens on a D40 it 'effectively beecomes' a 75mm lens. Put the same lens on a Full frame camera like the D3 and it's back to 50mm.

[idiot mode]

Why?

[/idiot mode]

It's the crop factor of the sensor. It doesn't make the lens behave like a lens with a 75mm focal length, just that the image will appear as though, taken from the same position, it was taken with a 75mm lens.

If you stand at position X and point your full-frame camera + 50mm lens at a subject, say a house, then the light from the lens will cover the whole sensor. It's footprint if you like. Print the picture on A4 sized paper.

Then, from the same position, put the lens on the cropped sensor camera. First thing you'll notice is that the subject fills more of the frame. This is because the footprint from the lens is the same, but the light is falling on a smaller sensor. Print the image on A4 sized paper again.

Now comparing the two side by side, you'll find that you have the same sized photograph taken with the same lens, but when it's on the cropped / DX sensor camera it looks like you've used a telephoto lens to get closer to the subject.

Hope that makes sense.

[GetCarter]

/\ wot he said

[SamHH]

Nicked from another website: