Mirror lenses have an easy tell, the so-called donut shaped boke pattern they produce in the out of focus highlights of an image. Of all the catadioptric lenses I have ever had the opportunity to use, the old mirror Nikkor 500 mm f/8 (close focus version) is possibly the most unique. That is down to its ability to focus to just under 5 feet (1.5 m). In other words, the lens is basically a close-focusing telescope. On a camera with a micro-four thirds sensor, the field is reduced by a factor of two compared to a piece of 35 mm film. Using a tripod, I was able to get a few molecules of the orchid petals in sharp focus.
