Beginner What size lens is equivalent to an "old" 50mm

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18,912
Name
Alan
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No
#3
If you have a Canon APS-C then it's focal length / 1.6 so 31.25mm is the Canon APS-C equivalent of full frame 50mm.

If you have Nikon APS-C it's 50/1.5 so 33mm is the Nikon APS-C equivalent of 50mm on FF.

If you have MFT the crop is x2 so a 25mm lens would be the equivalent of 50mm on FF.

If you have a FF DSLR then 50mm is 50mm :D

Sorry to repeat what Andrew said, I must have been typing as his reply appeared :D
 
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308
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#4
It depends of the crop factor, which is determined by sensor size. A full frame DSLR will be the same as the 35mm format, ie it would still be a 50mm lens. Assuming you mean a crop sensor DSLR, which is a crop factor of about 1.5x, 35mm will be what you're after. M43 cameras have a crop factor of 2x, so they need a 25mm lens.
 
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Name
Mike
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#8
I assume the question, is: "what is the 'normal-angle' lens length for.....{insert camera format of interest}"
It 'depends' on the projection-plane.... ie film size or sensor dimensions.
The 'rule of thumb, is that the 'normal' angle lens is one with a focal lenth the same as the diagonal of the focal plane.....
On a 35mm film camera or 'full-frame' widgetal, the film-trap is 24mm x 36mm, and the diagonal of that is.... 43mm.. BUT that film-trap/sensor is oblong.... take the long-side, 36mm and make a square that size, the diagonal is nie on 50mm. Go Medium format, and with 6cm wide film, you can put an oblong on that either side of a square, from 4.5x6, 6x6 or 9x6... and the 'normal lens, can be anything from 75mm to 110mm.. if you go by the actual diagonal, not the square of the longest side....
Make sense?

An APS-C sensor is sized on the old APS sized film, which like 120 offered some alternative masking frames on film aprox 24mm wide,(as oposed to 35mm for 35mm, or 6cm for 120 roll-film), which like medium format gave a range of potential 'normal' angle lenses by the strict diagonal, or the diagonal of long-side square.... 'around' 35mm..
Which, taking the Nikon 16x24mm croip sensor is 'about' its normal angle lens-length... give or take.... and anything in the 30-40mm region is about the 'normal-angle' for a crop-sensor camera....

BUT, a lens is a lens is a lens, and its focal length is its focal length.... the 'equivalence' this gives is ONLY for the angle of framing. A 50mm lens is still a 50mm lens whether its got a 35mm sized 24x36mm film trap behind it, a 16x24mm digi-sensor or a 6x5cm bit of roll-film.. the focus you get, the perspective you get, the Depth-of-field you get is the same... all that changes is how much you lop off the top-bottom-and-edges in the 'crop' to get the same effective framing or angle of view... and that''s as far as the 'equivalence' goes.
 
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825
Name
Alistair
Edit My Images
No
#9
I assume the question, is: "what is the 'normal-angle' lens length for.....{insert camera format of interest}"
It 'depends' on the projection-plane.... ie film size or sensor dimensions.
The 'rule of thumb, is that the 'normal' angle lens is one with a focal lenth the same as the diagonal of the focal plane.....
On a 35mm film camera or 'full-frame' widgetal, the film-trap is 24mm x 36mm, and the diagonal of that is.... 43mm.. BUT that film-trap/sensor is oblong.... take the long-side, 36mm and make a square that size, the diagonal is nie on 50mm. Go Medium format, and with 6cm wide film, you can put an oblong on that either side of a square, from 4.5x6, 6x6 or 9x6... and the 'normal lens, can be anything from 75mm to 110mm.. if you go by the actual diagonal, not the square of the longest side....
Make sense?

An APS-C sensor is sized on the old APS sized film, which like 120 offered some alternative masking frames on film aprox 24mm wide,(as oposed to 35mm for 35mm, or 6cm for 120 roll-film), which like medium format gave a range of potential 'normal' angle lenses by the strict diagonal, or the diagonal of long-side square.... 'around' 35mm..
Which, taking the Nikon 16x24mm croip sensor is 'about' its normal angle lens-length... give or take.... and anything in the 30-40mm region is about the 'normal-angle' for a crop-sensor camera....

BUT, a lens is a lens is a lens, and its focal length is its focal length.... the 'equivalence' this gives is ONLY for the angle of framing. A 50mm lens is still a 50mm lens whether its got a 35mm sized 24x36mm film trap behind it, a 16x24mm digi-sensor or a 6x5cm bit of roll-film.. the focus you get, the perspective you get, the Depth-of-field you get is the same... all that changes is how much you lop off the top-bottom-and-edges in the 'crop' to get the same effective framing or angle of view... and that''s as far as the 'equivalence' goes.
Seriously Mike, you need to keep your answers a bit shorter. Particularly as this is the beginners section, you're likely to bamboozle them and they'll get lost, even if the answer is in there somewhere.
 
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