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Old Feb 25, 2005, 3:22 PM   #1
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I was looking at specs for various SLR lenses and noticed that lenses with the same focal length can have quite different magnification. What's up with that? :?

For example, Canon Zoom Telephoto EF 70-200mm f/2.8L 1:7.7, Canon Zoom Telephoto EF 70-200mm f/4.0L 1:4.8 :O
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Old Feb 26, 2005, 5:42 PM   #2
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I think you are not understanding the nomenclature correctly. Magnification factor is not a normal parameter included in lens description. That number after the "1:" is NOT magnification factor. It is the largest lens opening (lowest f-stop) available. I am looking at a Nikon 80-200mm zoom lens. Under the zoom range is printed "1:4.5-5.6 D". In this case, the 4.5 is the maximum aperture at 80mm and 5.6 is the maximum aperture at 200mm. The "D" indicates that this lens transmits distance information to the camera CPU.

I am not sure what the "1:" refers to. I did some searching online for lens nomenclature but was not able to find anything. I found loads of technical information and formulae on lens optics but no information on the "1:..."

I wish I could help you more.

Cal Rasmussen
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Old Feb 26, 2005, 5:59 PM   #3
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Thanks Cal. The magnificationnumbers come from B&H Photo. I don't know where they got them.

http://www.bhphotovideo.com/bnh/cont...#goto_itemInfo

http://www.bhphotovideo.com/bnh/cont...#goto_itemInfo


D'oh! I think I figured it out. They're talking about magnification at minimum focusing distance. So a macro would be 1:1 or 1:2, but a non-macro would be some higher ratio depending both on minimum focusing distance, and focal length. :idea:
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Old Feb 26, 2005, 8:00 PM   #4
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I think I know the basic answer to your original question. If both of thse lenses are combination macro/zoom lenses, the optics for the macro end of the zoom range are probably quite different between the two lenses. Magnification only occurs at the macro end of the zoom range. This would account for the different magnification factors.

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