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Testing new lenses...

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Author Topic: Testing new lenses...  (Read 513 times)
brianb
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« on: March 26, 2009, 02:03:57 am »

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When you put a 10mm fisheye on a 1.6 X crop DSLR how doers that affect it. ? Doesn't it become 16mm ? I assume you will still get that 'bowl' effect because of the design of the lens.
Yeah, the fisheye distortion is designed in. 10mm on an APS-C format camera looks like 16mm on a full frame camera .... now a fisheye can either be "diagonal" (180 degrees corner to corener) in which case 16mm is "normal", or "circular" in which case the field (half the sphere) is a circle touching the short edges of the frame & 8mm is "normal".

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You get vignetting up to  14mm on a regular wide angle on a  full frame camera,
Eh? You do tend to get vignetting on all lenses but it needn't be severe at any focal length. You can actually have a rectilinear (non distorting) lens with a shorter focal length than a circular fisheye ... a distortion free design has to vary its focal length, increasing towards the edges of the frame, so the focal length would actually have to go go zero to cover the full half sphere field of view.
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