Excerpt: The lens has performed as expected based on reviews. Focus is sensitive - I've found best to use preview zoom of the camera and practice delicate adjustments. I think this has been a great experience in ultra-telephoto photography - the sensitivities of to wind, gentle breezes, slight vibrations in the ground, and heat distortion. Even the earth rotation when photographing the moon was more than expected.
Excerpt: I want to put this lens in perspective. Look around the Adorama site for an 800mm lenses and you'll find some nice ones for $6,000-$15,000. You'll also find this one for less than $200. There are real reasons for the price difference. Don't have high expectations, have some fun with it, and you'll do OK with this lens.The lens is lightweight as all mirror lenses are. If you shoot in B&W there are threads for 30.5mm filters on the back of the lens (closest to the camera).
Excerpt: I'm giving it one star because I can't achieve focus. If a lens doesn't focus, it's not a lens, it's just a piece of glass. On a tripod, but am unable to get a good focus. I don't expect tack sharp, but I didn't expect ghost images either. Might be the one off that has a problem, not sure. Am returning the lens after I get home and see if a replacement works.
Summary: Perfect compromise between features and cost. Touchy to focus, a bigger viewfinder or magnifier would help, but once focused the picture quality is very good. A bit heavier, so it made my "inexpensive" tripod shake more. But I was able to get images that just weren't possible with my other lenses. A very good buy.
Excerpt: I just bought this lens and was hesitant after I read some of the reviews of manual focus mirror lenses of this type. It has exceeded all my expectations. I have been able to get some extremely sharp pictures of great blue herons in flight. I had one image where the out of focus donuts were a problem but I think this lens is every bit as sharp as a high end lens from Canon or Nikon.
Pros: Consistent Output, Durable, Easily Interchangeable, Strong Construction