I was really skeptical at first ... a good telephoto lens for that price? The image quality is really good and if you manage to master the manual focus, you can make very good pictures with this lens. This requires a stable tripod, because without stability caused even a breath of wind blurs. By design annular Bukehs are naturally present. Other than that I can find ... no vignetting aperture of 6.3 is not bad for a 500mm lens, but you can not adjust what you sometimes wish for in a mirror telephoto. The slightly lower contrast display can be easily compensated in the RAW post. I can wholeheartedly recommend it really, if a ring-shaped Bukehs not disturb! :)
