I just bought a used Sony 40mm f2.5 lens and tested it on my Sony A7rIV.
It s sharp at every aperture, over the whole frame from f2.5 on. However, there is a portion on the lower edge of the frame which is less sharp - the last 5% from the edge I would guess. Oddly, both corners are still very sharp.
I tested this several times, and it is repeatable, even when I put the focus point at the bottom of the screen.
Even odder, it is worst at f4, almost gone by f5.6.
What could this be? How could f4, be consistently less sharp in this area than at f2.5?
Last I have seen something similar occurred when adapting the Leica 35/2.0 ASPH version I on my Sony A7R. This lens was known to have an issue with this Sony sensor. A bit unusual in you case since you stay in the same E-mount lens environment.
wolfloid wrote:
I just bought a used Sony 40mm f2.5 lens and tested it on my Sony A7rIV.
It s sharp at every aperture, over the whole frame from f2.5 on. However, there is a portion on the lower edge of the frame which is less sharp - the last 5% from the edge I would guess. Oddly, both corners are still very sharp.
I tested this several times, and it is repeatable, even when I put the focus point at the bottom of the screen.
Even odder, it is worst at f4, almost gone by f5.6.
What could this be? How could f4, be consistently less sharp in this area than at f2.5?...Show more →
The first thing I always do with a brand new lens is a centering test. Doing that upfront can save you a lot of time later when trying to figure out what's causing an issue. Also, make sure to turn off IBIS when you're testing lenses.
