I have just received my new Sigma 14-24 f2,8 DG DN. Please, would someone tell me how to check corner consistencies?
Do I have to focus on the same object on each extreme corner? Or should I focus at middle point and then recompose, without focusing again, to the same object on every extreme corner?
Thank you very much
Best
You will get the most accurate indication of how well centered a lens is by focusing for one corner and then checking that against the the other corners without refocusing. This gives a more accurate indication than center focusing for which field curvature can soften all your corners, making small differences harder to see. I like to use the same object placed in all four corners (without refocusing) because then you also are comparing the exact same structures.
Hi rvh23
Then you suggest this a more accurate test than focusing center at infinity and then recomposing for every corner?
Supposing that your method keeps field curvature excluded from the equation, it may be indeed.
I tried some not very formal tests today and I start to suspect that left side is somewhat softer than the right side at f2,8. I suppose that this pattern will repeat itself at any aperture... Or does it get better at higher number diaphragms?
Thanks a lot for your answer. Tomorrow I'll check both methods.
Best
Oct 10, 2019 at 04:43 PM
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