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Old Apr 27, 2008, 9:52 AM   #1
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I cannot get a maximum aperature of f/3.5 on my EF 28-135mm f/3.5-5.6 IS USM. Even having the ISO set at 1600 in direct sunlight I can only get a max of 5.6 Any ideas?
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Old Apr 27, 2008, 9:56 AM   #2
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It's a variable aperture lens. It is only 3.5 when at it's widest zoom (28mm). As you start to zoom out the max aperture changes to 5.6. I never bothered to map out exactly what focal lengths the max aperture changed at though.
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Old Apr 27, 2008, 12:38 PM   #3
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John is right and frommy experience with variable aperture lenses nearly all will change from their widest aperture almost the instant you start to zoom and at the long end you usually find that you have quite a lot that is at the long widest aperture.
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