AvTvM said:infared said:This is an "automatic' aperture" lens. It keeps the aperture open and it closes down to your actual setting only at the moment of exposure. You can push in you DOF preview button in MF or AF mode to close does the lens aperture see your actual depth of field at any time.
"see" - yes.
But to my knowledge the camera will still AF with fully open aperture, no matter whether DOF preview button is pressed or not.
The only workaround I know of for the entire problem of focus shift on Canon cameras with EF lenses is using (different) AFMA settings at different apertures. Which is, what the guy asking seems to be doing. Of course it is not really an "elegant" solution in the field.
Quite honestly, I did not know that focus point could "shift" due to aperture change???
Is that a quirk of the mechanics of this particular lens? ...or is it a universal truth (physics) for all lenses?
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