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.
>bottom.

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.

Dario 





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