...
I was unimpressed with results on my GF-1 using Leica lenses or less than 50mm fov. The edges were not just soft, they were distored and unfocussed. In fact, I was complimented in this forum for seeming to have sharp results using my much wider CV 15/4.5 on my GF-1 but in fact it was a con on my part because I cropped off the offending areas.
I could only get decent results with wide angle lenses if I stopped down significantly and/or cropped, e.g. f16 which kind-of negates the beauty of fast Leica glass. It is acknowledged elsewhere in this forum and in threads on the internet that for reasons of physics I don't understand third party lenses of less than 50mm do not fare well on m43rds bodies. As you probably know Panasonic apply all sorts of software fixes to correct the distortion in their own lenses.
...
Louis,
It makes sense, although I think your comments are a little over-stated given what I see above as an example.
Digital sensors do impose more constraint on how far off the orthogonal an incident ray trace can be before they start acting weirdly, and film-camera RF lenses are designed for shorter mount registers, shorter primary nodal point distances and stress this aspect by having more oblique incidence to the corners and edges of the frame. SLR lenses in the shorter focal lengths, by the very nature of their inverted telephoto design to fit on the mount register and clear the mirror mechanism, avoid these problems for the most part until the focal lengths become very short: the primary nodal point is drawn further from the imaging plane which naturally allows a more orthogonal angle of incidence at the sensor, even without special attention to doing so in the optics.
My interest here is not ultimate high-speed, ultra-wide lenses, however. My interest is in a compact, modest-speed lens in the wide-normal to short-portrait-normal range (20-28mm) that will be used mostly at relatively stopped down lens opening (f/5-f/8). So much of these issues will, in practical terms, likely not be evident in the image captures. Most of my other experience with adapted lenses has been with SLR lenses, most of which have performed quite well edge to edge.
An exception is my Cosmicar-Pentax 12.5mm f/1.4 TV lens. Here the benefits of a lens designed for a digital sensor are readily apparent: the image circle doesn't quite cover the entire FourThirds sensor format, but I can see easily that it is sharp and crisp, even wide open, right to the edge of the image circle. It should also be noted that this lens is deeper than the Panasonic 14mm as well:
I'm looking for modest price, modest speed, satisfactory performance at a compact size in a manually operated lens. Perhaps I toss the cost and compact notions out the door and just order a Nokton 25/0.95 in the end ... ;-)
Of course, if I go this way and I really want an ultra-performing 25mm lens, I could just stick my Summilux-D 25mm f/1.4 ASPH on the adapter and use it... !
.. As you probably know Panasonic apply all sorts of software fixes to correct the distortion in their own lenses. ..
Panasonic applies a very fast and mathematically simple set of rectilinear and lateral chromatic aberration corrections as a part of their lens design. It's all part of our migration to practical and useful computational photography, ya know ... ];-)