Why does nikon....

Started May 28, 2013 | Discussions thread
Terry Vickers
Regular MemberPosts: 332Gear list
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Re: no such thing
In reply to sshoihet, May 28, 2013

Focal length in photography is the distance of the rear nodal point of the lens to the image plane.

The formula for FOV = 2 arctan (x / (2 f) where x is the diagonal size of the sensor.

Obviously by changing the x above it will change the FOV regardless of the focal length.

FOV or AOV would probably be a more accurate way of naming lenses in terms of their "zoominess" but it's one of those conventions that has stuck. So we have to use the crop factors to get traditional 35mm FOV equivalents. While a bit of a confusing I think it would be more confusing to call something that it isn't ie. calling a 35mm focal length 50mm when it is in fact 35mm.

The use of equivalents is mainly there to have a commonly understood reference. More convention than anything else.

 Terry Vickers's gear list:Terry Vickers's gear list
Nikon D3100 Nikon D7000 Nikon D5200 Nikon AF-S DX Nikkor 55-200mm f/4-5.6G VR Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR +7 more
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