Paula at Linhof & Studio Ltd has uploaded additional material, supplied by Silvestri, relating to the Apo-Silvetar 5.6/35mm lens:
(a) a set of six images from a Fujifilm GFX 50 camera, in both raw and TIFF formats.
(b) a PDF of technical data comprising a graph for relative illumination and two graphs for MTF.
The downloads are available from the order page here:
Silvestri Apo Silvetar 5.6/35 mm (linhofstudio.com)
The individual images can be quickly previewed on the Google Drive page by clicking on the first filename, and thereafter advancing to the next image using the arrow button on the right.
My first impressions are:
So far I've looked at the preview images only to judge the amount of distortion. The first image shows surprisingly little distortion in the vertical columns. The second image shows moderate barrel distortion in the horizontals. Subsequent images are obliques and do not help much in evaluating distortion.
According to the graph of relative illumination, the illumination falls to 60% at the midway point and to 17% at the edge of the field radius of 37.5mm. The mid-point value of 60% is typical. The edge value of 17% is more than 2 stops, but similar to that seen in the Digaron-S 35mm. A centre filter may be beneficial. Note: The aperture used in the test is not specified.
Two graphs of MTF are given. Unfortunately, neither graph is labelled with the lens aperture used, so until we are told, we will have to guesstimate. One graph specifies the field radius in mm and the other does it in degrees, but that difference is inconsequential.
The first MTF graph, on page 2, is new to us. It shows very high centre performance, similar to the Digaron-S 35mm lens at f/5.6, and much weaker performance in the mid-field and edge. Accordingly, my guess is that this graph shows the MTF of the Apo-Silvetar 5.6/35mm lens wide open at f/5.6.
The second MTF graph, on page 3, is the one we've already seen in the lens brochure. It shows slightly lower, though still very high, centre performance that extends well into the mid-field, similar to the Digaron-S 35mm f/4 lens at f/8, with very good performance at the edge. Accordingly, my guess is that this graph shows the MTF of the Apo-Silvetar 5.6/35mm lens at a similar f/stop, likely either f/8 or f/11.
Whatever the latter aperture is, this excellent resolving power - at an affordable price - is what this lens is all about.
I've sent a request for some further details to Silvestri.
Rod