Shouldn't a 50mm lens give a slight zoom on a DX camera?

miurasv

miurasv

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Steve.
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Just been playing with my new Nikon 50mm 1.4 G AF S on my D40 and the images seem to be slightly further away when I look in the viewfinder and not closer as I thought they'd be. Can someone please explain or is it just me? Thanks in advance.
 
you'll have a 90/95 % viewfinder i think which means you'll be missing a little from around the edge that will show up on the photo

which i presume will make your scene look less "cropped"
 
alexkidd said:
you'll have a 90/95 % viewfinder i think which means you'll be missing a little from around the edge that will show up on the photo

which i presume will make your scene look less "cropped"
Click to expand...

Thanks for pointing that out as not being very observant I hadn't noticed that but unless my eyes are playing tricks on me the image I can see looks further away. Is this normal with a 90/95% viewfinder? Shouldn't the image look closer as I understood anything over 35mm should have a telephoto effect?
 
Nope, you're just seening a portion of what you would see with a lens of the same focal length on a full frame sensor. the optics stay the same, it's just that less information is recorded by the sensor.
 
OK

Imagine the 50mm is on a Full Frame (FF) camera, take a portrait while standing at the correct distance to just get both ears in the shot.

Now change the camera to a DX, the lens will be the same but the sensor in the camera is smaller than the FF so you will be missing the ears, however the eyes will look the same size in both cameras as you are using the same lens at the same distance. You could even focus the lens onto a piece of paper and the eyes would be the same size.

To get the ears in the shot with the DX camera you have to move back from the subject until the ears are just in the shot again, on a FF camera you would have to use a 75mm lens from this further distance to get the same framing. This is where effective focal lengths come in, the focal length does not change just the angle of view that the sensor can see.

If you print shots from the FF and the DX taken from the same distance with the same lens and both prints are the same size then the DX shot will have to be enlarged more than the FF shot so then the eyes will be larger and it will appear to have been taken with a longer focal length lens.

You can get exactly the same effect of a DX camera by using the FF camera and just cropping the image later.
 
alexkidd said:
you'll have a 90/95 % viewfinder i think which means you'll be missing a little from around the edge that will show up on the photo

which i presume will make your scene look less "cropped"
Click to expand...

i would have thought a 90 - 95% finder would make it look more cropped , anyway is the op maybe thinking of the viewfinder magnification when he looks through the finder ? ( which maybe dosnt equate to the lens on the front )??
 
i should have clarified, less cropped on screen, more cropped through viewfinder :)
 
donutagain said:
i would have thought a 90 - 95% finder would make it look more cropped , anyway is the op maybe thinking of the viewfinder magnification when he looks through the finder ? ( which maybe dosnt equate to the lens on the front )??
Click to expand...

Yes, I think the OP is maybe talking about viewfinder magnification. I think the D40 is 0.8x, which is always quoted with a 50mm lens at infinity focus.

So if you put the camera to one eye and leave your other eye open, the viewfinder image will look a bit smaller.

Edit: the OP talks about "slight zoom" but zoom refers to a type of lens, ie one with variable focal length. You can have both wide angle and telephoto zooms, and standard zooms inbetween (usually called the kit lens).
 
Suvv said:
OK

Imagine the 50mm is on a Full Frame (FF) camera, take a portrait while standing at the correct distance to just get both ears in the shot.

Now change the camera to a DX, the lens will be the same but the sensor in the camera is smaller than the FF so you will be missing the ears, however the eyes will look the same size in both cameras as you are using the same lens at the same distance. You could even focus the lens onto a piece of paper and the eyes would be the same size.

To get the ears in the shot with the DX camera you have to move back from the subject until the ears are just in the shot again, on a FF camera you would have to use a 75mm lens from this further distance to get the same framing. This is where effective focal lengths come in, the focal length does not change just the angle of view that the sensor can see.

If you print shots from the FF and the DX taken from the same distance with the same lens and both prints are the same size then the DX shot will have to be enlarged more than the FF shot so then the eyes will be larger and it will appear to have been taken with a longer focal length lens.

You can get exactly the same effect of a DX camera by using the FF camera and just cropping the image later.
Click to expand...



Right, at long last I get it now. I thought that with a DX camera objects would appear 1.5 X closer than they would on a FX camera which isn't the case and no zoom telephoto effect at all. I understand why they're called crop sensors now too so thanks very much for that. To get my head around it totally I'm going to have to play with my camera. Thanks again and to all that replied.
 
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