Originally posted by MJSfoto1956 first observations:
DA 35mm Macro: the corners don't sharpen up until f/8. But strangely, if you look VERY closely at the f/2.8 is is actually slightly sharper in the lower right corner than f/4 or f/5.6 (check out the chain link fence near the garage). Clearly f/8 is the "best" but I wonder why f/4 and f/5.6 in the lower right corner don't quite match? Is there any possibility of slight refocus between exposure here? Or is this a classic case of "focus creep"?
Very interesting.
Michael
DA 35 Macro.
At F2,8 it is sharper than at 3,2 and 3,5.
Sharpness improves at 4,0, but not substantially.
F4,5 shows slight improvement in the centre of the frame, while the corners still lag behind.
F5,0 the centre of the frame is now sharper, while the improvement in the corner sharpness is marginal.
F5,6 is where the corner sharpness starts noticeably improving. Centre is top-notch.
F6,3 to F8,0 both corner and centre sharpness improve.
F9,0 is the point where there is no increase in centre sharpness, while the corners are still becoming more detailed.
F10. Diffraction starts to affect the centre of the frame, while the corners are still improving.
With the aperture from 2,8 to 5,6 the sharpness in no uniform across the frame. Some corners are sharper, while the other are softer. This observation makes me wonder.