BrandonSi wrote:
Speaking of copies.. I hesitate to ask this.. what do you think of the results here? This is f/4 @ 12mm. I feel like it's pretty solid but this is my first time checking a lens like this.
If this is a high resolution sensor, it doesn't look bad for extreme corners at 12mm, which is the lens' weakest focal length. If you are happy with your results at your usual shooting apertures, I can highly recommend not worrying about this too much.
If you've followed this thread, you'll know that I've tried 8 copies of this lens, and never found one that was perfect across the whole zoom range. The corner sharpness variations arise from both tilt and decentering effects. The tilt can be affected a much by your camera's mount as the lens'. If you can get sharp details wide open when focusing on each corner in turn, but not if you don't re-adjust focus each time, you are dealing predominantly with tilt. If the effect of tilt is consistent across the range, shimming can improve your results. If the tilt varies across the range, less so.
My experience has been that only one of the 8 copies I tried was unusably decentred (over the whole range) even stopped down to F8. The rest had differening strengths and weaknesses. So you might find a copy that is better than what you are showing here at 12mm, at the expense of having worse performance at 24mm.
That said, I did see more variation at 12mm than any other part of the range, and the copy I settled on in the end is still a little decentered wide open at 12-13mm. Also, at wider apertures field curvature is very obvious at 12mm, so if your shot was center-focused, you will not be seeing optimal performance in the corners. Better to focus on one corner (preferably one with optimal focus near the middle of the 4 best focal distances) to make this assesment.
Jan 05, 2021 at 06:51 PM
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