DA star 50-135

Dario Bonazza dario.bonazza at virgilio.it
Wed Dec 4 11:00:10 EST 2013

>CollinB wrote:
>Just take a photo of a flat surface (the classic brick wall test, for
>example) perpendicular to the camera/lens. Focus in the center with
>the lens wide open. Look at the resulting image and check that the
>left and right edges are *equally* sharp; do the same for the top vs.

And try several focusing distances, because many of those lenses perform 
fine at certain distances and disalign badly at others.
Typical failures happen at intermediate focusing distances  (e.g. around 
1-to-3 meters, or 3-to-9 feet), while usually even poor lenses perform well 
at closest distance and infinity.


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