Voigtlander 35mm f/2 APO-Lanthar Review

tsdevine wrote:

Any samples, or are they literally dupes of Fred's first copy? I haven't noticed any field curvature in mine up to this point, but I've only had a chance to shoot it once.

inksandpaper wrote

I've looked at two copies so far and both have noticeable field curvature, bending further away off axis. Both are reasonably straight copies with regards to swing and tilt, though not perfect. The field curvature is enough to ruin corner sharpness roughly to the degree that Fred's original copy was, by my estimation. Has anyone else experienced the same? I'm not sure what I should do. Is reverse field curvature expected from this design and Fred just got super lucky?

The field curvature is bad enough that My Sigma 35 1.2 DG DN is quite a lot sharper than my CV 35/2 off-axis at F2 and F2.8, despite the former also suffering from field curvature, except it is forwards field curvature.

Here's a folder of 5 raw files of from both lenses. https://www.dropbox.com/sh/s7eyv9mv7egbhjn/AAAEywwQ5fSuhxha__1IFg9na?dl=0

A matching pair from each of the two lenses which show reverse field curvature, more easily visible in the horizontal frames. Vertical frames included for anyone interested to verify focus plane tilt. The one labelled "other copy" also shows asymmetric field curvature, curving away strongly on the right edge more than on the left. One more raw included from the copy I have on hand which shows field curvature with a slightly different scene.

Edit: Added two more raw files. Distant landscape view at F2, a7R II, from V35 and Bigma 35mm (S35). Notice how the top left and right corners fall away because of the field curvature which puts the plane of focus further than infinity. And down the left and right edges the image looks somewhat astigmatic due to being out of focus. The Sigma, while not perfect, looks pretty good almost everywhere.