Inspired by Hamiltonian on DPR, I applied Roger Cicala’s field curvature visualization method (Photoshop: Filter -> Stylize -> Find Edges) to the 45-100/4, at putative focal lengths of 45, 60, 80, and 100mm:
Top left is 45mm, top right is 60mm, bottom left is 80mm, and bottom right is 100mm. The top composite is grass, the bottom is gravel.
The field curvature is mild, and occurs at the short end, which is what the earlier screening tests indicated.
Thank you Jim and than you Roger!
I was aware of the technique, but I think it may make some sense to look at the field curvature to optimize sharpness.
If we shoot landscape, it may make sense to focus on a point away from the optical center, but we would probably like to put focus in a place where the gradient is even and avoiding local minima.
Doing this simple test may make a lot of sense!
Best regards
Erik