zhangyue Offline Upload & Sell: On
|
Phillip Reeve wrote:
The critical point is of course in determining how much of a difference between the corners is too much. Distortion, field curvature and coma are of course affecting and wide angle to varying degrees but I don't really see why they should be a problem, they should affect each corner the same.
My question about this testing are:
A, lens with Astigmatism and coma is hard to judge critical focus at extreme corner this way . For lens having astigmatism, you potential have two focusing location having similar in focus perceptive plane or any optimized focusing between judged by you, hence prone to human error.
B, The focus and recompose error should be negligible in this case, but focusing use corner by moving around camera focal plane is problematic to me, especially for WA and SWA, because it alter light angle hit on the sensor with cover glass which change lens FC and Astigmatism characteristic as well.
Anyway, the difference itself seem strong enough to indicate the decenter but it is really not a optimized way with unnecessary complication IMO.
|