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Old Mar 13, 2007, 12:38 AM   #1
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I have just purchased my first DSLR, Rebel Xti and the EF 28-135 USM IS. I love my equipment but I have a question regarding EF and EF-S mounts. If I want to know the 35mm equivalent zoom for the rebel do I have to always multiply the numbers on the lens by 1.6? Does it always go the same way regardless of EF or EF-S lens that I have? Let's say if I put an EF lens on a 5D, do I still need to multiply by 1.6 even it is a full frame camera? Thanks for all your help guys!
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Old Mar 13, 2007, 5:38 AM   #2
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The 5D has a full frame sensor, the same size as piece of 35mm film, so there is no multiplication (crop) factor. Same goes for the 1Ds Mark II. The XT, XTi, 30D, 20D all have a smaller sensor so to get the 35mm equivilent field of view you need to multiply by 1.6 for EF or EF-S lenses. The 1D Mark IIn and the new 1D Mark III both have a1.3 crop factor. So your 28-135mmhas the 35mm equvilent field of view of a 45-216mm lens.
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