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Anonymous
>>82058 On 35mm film cameras, 50mm is generally referred to as "normal". I.e., it's about the angle of view your eye would see unaided. Longer focal lengths are telephotos, shorter are wide-angle.
However, that only goes for 35mm film and full-frame digital. Most digital SLRs, including your XTi, have a sensor that's smaller than the 24x36mm of a 35mm film frame.
The upshot of this is that it's like taking a crop of the middle of the frame, which acts a lot like increasing the focal length in practice. Your XTi has what's known as a 1.6x crop factor, so to figure out the 35mm-equivalent field of view of a lens, you have to multiply the focal length by 1.6.
So, a 50mm lens on your XTi acts like an 80mm lens would on a film camera. If you want a normal-length lens, you need to take 50mm divided by 1.6, or 31.25mm. So the 30mm f/1.4 from Sigma would be a more or less normal focal length on your camera.
Other good choices are Canon's 28mm f/1.8 and 35mm f/2.0 (which is what I have as my fast normal prime). The Sigma is notoriously bad at accurately focusing on Canons, but the genuine Canon lenses don't have those problems.
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