The restrictions are all explicitly in the product description or implicitly listed: Manual focus, fixed iris, fixed focal length, image stabilization, no EXIF data. In addition, results from the fact that it is a mirror lens, the shape of the bokehs. The depth of field is the same as with any other 500 / 6.3 lens.
Who has no application for such a lens, thus not allowed to access. For me, the application is Zoofotografie what happens to me often. For a real Zooobjektiv you can very quickly get rid tenfold to Euros, so I found the offer interesting.
I was not at the zoo (I then update this review). But I could still have intensively tested and am very satisfied. There is no distortion or TCA. The vignetting is weak and easily remedied. There is a slight curvature of field, that is, if the center is sharp, the edges are slightly out of focus and vice versa. Would goofy for architectural or street photography, but something with 500mm? A bit of a shame is the longitudinal CA which ensures exceptionally clear purple fringing when UV light is in play (daylight, fluorescent tubes, lightning). Can digital odometer, or use a band edge filter that closes down below 420nm, but I was hoping that mirror optics are good-natured since.
The contrast is weak indeed. This is due to scattered light, because the lens is almost as short as thick. I knew that on the basis of other reviews and ordered parallel at amazon.com (ie in the USA), a lens hood (Desmond Metal 95mm Telelens Hood Shade 95 Telephoto, 16 incl. Shipping). Contrast problems I see now no more.
Now for focusing. This is likely to be most critical for most prospects. I have a NEX-7 with an electronic viewfinder, ie focus peaking and magnifying glass in the viewfinder. So I've had in my tests only minor problems with the focusing, even with free hand. It may well be that this is not so go to a DSLR readily. I do not know how widespread focus peaking now is. But without such a focusing aid I would be very careful with the purchase. I think without having tried it, that my yield would be noticeably smaller with optical viewfinder and split-image rangefinder.
Non-shaky shots freehand I do not find difficult to do, however. In a stable position I can from 1 / 200s to avoid motion blur, from 1 / 500s can I exclude them in any situation. In burst mode, I'm from 1 / 60s successfully. In visits to the zoo I have I already illuminate briefly because of the animals. The 500mm / 6.3 agree about. It is my measurements so ineffective an f / 8 as is sometimes claimed. In bad light, there are tricks like high ISO setting, burst mode and merging of several high-ISO shots (my camera can even automatically). Incidentally, the lens causes as little torque that it can even hold my little Joby Gorillapod.
Last sharpness. I also own a good 210mm with all bells and whistles. If the Walimex in sharpness would significantly fall, I might as well just go take my 210cc and curtail the images. But it does not have as I confirmed photos from Siemens star. You really get more than twice as much details on the image in both directions. If you hit the focus.
All in all, I have the 160 well spent. 250 it would not be worth having but. Must it not also. Anyway, I look forward to the next zoo.
UPDATE: I was now twice with this lens at the zoo. The weather was not ideal, but the photos very nice. What I write above, everything has been confirmed. I have my test photo mitsame 1: Uploaded 1-enlarged under the product images. It's definitely a fair-weather lens, but if the weather is nice, it provides all the details that one can expect from 500mm focal length.
