In the late 1980s through the mid 1990s, I had a Reflex-Nikkor 500mm f/8 lens. The optical formula is known as a catadioptric, or mirror, lens. Astronomers know about this type of optic, but despite being a relatively cheap way to own a long-focal-length, lightweight lens, this design has fallen very much out of vogue with photographers because of a several significant shortcomings…
- The maximum aperture is small, typically around f/8, and because of the optical design is the only aperture available.
- Significant vignetting – darkening at the edges, so the f/8 is only f/8 in the center of the image, and the corners are more like f/16.
- The “bokeh,” or quality of the background, isn’t just ratty or ugly, it can be, in some circumstances, downright unacceptable.
I found that in the years that I owned it, my 500mm sat at the bottom of a bag of “extra” lenses I kept in the trunk of my car, and I seldom got it out and used it. By 1997, I had the magnificent Nikkor 400mm f/3.5 ED-IF, which combined with a teleconverter to form a 560mm that was very sharp.
The 500mm’s only trump card was that it weighed a third that of the 400mm. When I did make a point to shoot with it, results were quite disappointing. I’m surprised to see that nice versions of the 500mm are as much as $600 on eBay, which tells me it’s more of a fetish property.
The bottom line: if someone gave me a Reflex-Nikkor 500mm f/8, I might play with it for a day or two, but in the end I think I’d give it back.
I remember toying with the idea of a mirror lens, back when I was still new at digital photography and wanted an inexpensive telephoto… But I’m glad I didn’t pull the trigger on it.
There actually have been a few variable aperture catadioptric mirror lenses. The most well known one was probably the Ohnar 300/5.6 Mirror (also sold under other names such as Hanimex, Makinon, Panagor, etc.) that was sold in the 1970s and early ’80s. It was a weird bird for sure. The variable aperture iris was at the front of the lens, just behind the corrector plate. It affected T-stop but didn’t really make much difference with regard to depth of field.