I recently used a combination of online coupons and rewards points to “buy” a lens for no dollars, an Opteka 500mm f/6.3DG catadioptric, or “mirror,” lens. If you know anything about my cameras and lenses, you know that I have several lenses in this focal length range, all of which are better mechanically and optically better than this odd piece of hardware.
Catadioptric lenses use the same optical setup of concentric mirrors as very large space telescopes (like the Hubble) to fold the light path, making them much smaller than their refracting counterparts.
Why did I want one?
- I wanted to be able to teach first-hand about this class of lenses and how they work.
- I missed the first 500mm mirror lens I owned (a Nikon).
- I wanted to play around with it.
- Play around with it? Is that a real thing? Yes; to me there is no better learning tool than experimentation with the new and the unknown.
- I wanted to photograph it.
- I wanted to challenge myself to make good images with substandard hardware.
So what is this lens like?
- Mechanically, focus is super-stiff, but it may loosen up as I use it.
- Optically, I have been surprised that it actually has a sharp zone, though it is shallow and elusive.
- Though advertised as “f/6.3”, even the best mirror lenses are only that fast in the center of the image, and vignetting (falloff) is very noticeable, such that I estimate it is about f/11’s brightness at the corners.
- It is more compact and better-looking than my Nikkor was, though its engraving, metals and rubber grip ring all seem cheap.
- It uses a t-mount to connect to the camera (so you can change camera brands by getting a different t-mount), which screws into the lens, and can unscrew during focusing if it’s not tight on the lens.
- It came with the world’s cheapest teleconverter, a 2x, presumably so it could be advertised as both a 500mm and a 1000mm, but it’s impossible to use with the teleconverter due to a dark viewfinder image, an amplification of any camera movement, and the fact that even the best teleconverter is a quality thief.
- Mirror lens are noted for their unusual, doughnut-shaped bokeh, which this lens certainly exhibits. Most photographers regard this as “bad bokeh,” but I’ll be treating like a tool in the toolbox.
I’ve already gotten a couple of images shot with it in the daily, so in the strictest sense, it is a pro lens, though I imagine this a case of my ability to extract something decent from fairly weak raw files. Time will tell, I guess, if this nonvestment was worth it, but so far, I’ve had fun with it.
Finally, a couple of posts ago, I talked about my lovely little AF-S Nikkor 35mm f/1.8 and why a young photographer friend of mine, Mackenzee Crosby, should buy it instead of the far more expensive Sigma 35mm f1.4, especially since the Sigma was made for a larger imaging sensors than she owned.
She ended up buying the Sigma, which she received as she was walking out the door to attend Monday’s Open Mic Nyte. She and I were able to play with it a bit, and I photographed it. It is heavy and focused smoothly, but I couldn’t tell much else.
I expect she was temped by the elusive maximum aperture, f/1.4, which is tempting. It’s hard for me to flaw her for wanting great hardware – when I was her age, I paid a small fortune for a Nikkor 50mm f/1.2 that turned out to be optically disappointing. I hope the Sigma works out for her. My only advice about it would be: wear it out.