Story written by our Used Equipment Buyer – Paul Brodek
So there’s kind of a lot of ground to cover today for just a puny little lens. What you’re looking at is a vintage Tamron 500mm f/8 Adaptall mirror/catadioptric/reflex lens, which is a mouthful. Mirror lenses, typically telephoto designs, are a very lightweight and compact alternative to standard glass-and-brass super-tele lenses. They aren’t easy to describe, but they basically use light bounced off of curved mirrors, instead of light reflected through multiple glass lens elements, to magnify the subject and deliver a sharp image to film/sensor. They look a lot like catadioptric telescopes, because they’re basically the same design. The mirrors greatly magnify the image and shorten the light path, and far less glass is required. So compact and lighter overall—check out the comparison with a Canon 400mm f/5.6.
Besides size/weight, mirror lenses eliminate some types of optical aberrations common to standard tele lenses, but they introduce one weird one of their own: out-of-focus specular highlights are annular, meaning donut-shaped. Mmmmm, donuts….. We included a photo to illustrate the Donut Phenomena.
Mirror lenses also don’t have aperture mechanisms. There’s no way to control how much light comes through the lens, so in the film world, where you can’t change your ASA/ISO rating from frame to frame, you can only control exposure with shutter speed, or neutral density filters. And that fixed aperture is usually not as fast as a standard lens. With a digital camera, which does allow changing ISO sensitivity from frame to frame, you do have more flexibility.
Oh, and one last weird mirror thing: filters can’t be attached to the front of the lens, they thread in _behind_ the _rear_ element. So you have to take off the lens to change filters.
So why bother with mirror lenses? Because they’re so much more compact and lighter than standard lenses, making them great for field use, and for occasional use. Oh, and they’re usually much less expensive than glass equivalents. And they’re terrific in the digital age, especially easy to adapt to mirrorless cameras.
We also need to talk about Tamron’s Adaptall system, which allowed a single lens, when paired with camera-specific Tamron Adaptall mount attachments, to fit many different cameras. Tamron made mounts for dozens of cameras, making life easier for multi-brand users.
Our sample is a not-for-sale demo lens, with some front elements scratches and a few internal fungus spots. Still gives a nice, sharp image. We’ve got another on tap, available soon. Retail is usually in the $125-$150 range for a clean one.