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p.21 #10 · 'Official' Post-PMA Discussion thread | |
RJJR wrote:
JohnnyGCanon wrote:
If I put my 100-400 on my 20D, the effective mm is 640mm. Right? In other words, if I had a 35 mm camera, it would be the same as a 640mm lens.
No it isn't the same as having a 640mm lens it's the same as taking a 35mm frame shot with a 400mm lens and cropping it to a bit smaller than a half-frame, but that crop happens to be located in the middle of the frame.
Now, with the 5D, it's effectively 400mm because of no crop factor. Must I crop every photo to get the 640? If so, that would be a pain.
You never "get the 640" you just get a cropped image (relative to the 35mm frame).
If you are using film, which is resolution-independent of the camera body, and if you put your long lens on an APS body, you would just get a cropped image, because you would (or at least could) still be using the same film.
With your lens on a digital body, the "film" resolution is a fixed parameter of the camera, and that is the pixel pitch. If the pixel pitch of the APS body is the same as that of the FF body, then you still just get a cropped image. But if the PP of the APS body is higher than that of the FF body, then you get a higher res cropped image, from the centre of the lens's image circle, so you can enlarge it more than would be possible with a crop from the centre of the FF body. Your true multiplier will not be the full 1.6x difference between APS and FF. however, unless you have the same total number of pixels in each camera's sensor.
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