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<blockquote data-quote="480sparky" data-source="post: 533915" data-attributes="member: 15805">It doesn't matter what aperture you set the lens to to take the photo with.&nbsp; What matters is what the maximum aperture is before you take it. Most bodies will AF down to 5.6 or 8, some of the higher-end one will do just fine at 11.&nbsp; The AF module sits below the mirror in front of the shutter.&nbsp; It uses the light coming in through the lens (which, at this point is at maximum aperture regardless of what you've set it at for taking the image).&nbsp; Some of the light passes through the mirror you see inside the camera, and is reflected down with another mirror behind that down to the AF module.Only when you take the photo does the lens close the aperture blades down to the set aperture.&nbsp; By this point, the AF module won't work because the two mirrors have been moved out and up so light from the lens can be controlled by the shutter.&nbsp; You can use a lens set to f/45 or f/64 or even f/90, and the AF will still use the lens wide-open to function.</blockquote>

[QUOTE="480sparky, post: 533915, member: 15805"] It doesn't matter what aperture you set the lens to to [I]take[/I] the photo with. What matters is what the maximum aperture is [I]before[/I] you take it. Most bodies will AF down to 5.6 or 8, some of the higher-end one will do just fine at 11. The AF module sits below the mirror in front of the shutter. It uses the light coming in through the lens (which, at this point is at maximum aperture regardless of what you've set it at for taking the image). Some of the light passes through the mirror you see inside the camera, and is reflected down with another mirror behind that down to the AF module. Only when you take the photo does the lens close the aperture blades down to the set aperture. By this point, the AF module won't work because the two mirrors have been moved out and up so light from the lens can be controlled by the shutter. You can use a lens set to f/45 or f/64 or even f/90, and the AF will still use the lens wide-open to function. [/QUOTE]

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