This lens is really long physically. It has only three lens elements, so I was sceptical about its optical quality. I was pleasantly surprised when I had the opportunity to test this lens on a Canon EOS 300D digital camera using an M42 to Canon EOS adapter.
The lens performs quite well. Colors and contrast are very good, and resolution is also higher than expected. In critical lighting situations there are some chromatic aberrations, but that is two be expected for such a long telephoto lens without the use of special glass elements. You have to use a tripod with this lens at all times.