This image could fit in this thread or in with the "Heligon"topic. Since it was captured using the shorter 50/0.75 Heligon, I put it here.
In general one try to make the lens come as close as possible to the film plane, in order to make it perform better by not being pushed as widely out of its designed domain. These lens in fact were extremely high quality performers using exotic high-refractive glass, and with a commensurate price as well. However, as their back focal distance ('register') is usually just a few mm, they are invariable abused and optically speaking compromised when mounted to any DSLR or even mirrorless cameras.
Contrary to what I expected, I found the best practical performance is not obtained by using the very shortest possible back focal distance, as the lens still is way outside its optimised conjugate distances and severe field curvature, spherical aberration, and astigmatism deteriorate the larger part of the capture frame. Best results so far has been with the lens on either my Panasonic GH-2 or the Nikon V1.
The capture of a Rudbeckia hirta is taken with the Panasonic GF-1. The image quality of this 12 MPix sensor does not do justice to the Heligon, though. The extremely shallow focused zone and the superb gradation into the out-of-focus background are endearing qualities of this exotic lump of glass and metal.
