LZOS MC Rubinar 500mm f/5.6 Macro (mirror)

One stop. At 500mm that is what this Rubinar gives you, and you pay for it with about 1.36 kg of glass and metal and a 105mm thread on the front. Most mirror 500s are f/8 designs, so on a grey afternoon this one lets you shoot at 1/500 where they would leave you at 1/250. On a tripod in good light the gap hardly matters. With a bird that won't sit still, it is the difference between a keeper and a smear.

LZOS built it in Lytkarino as a folded design. Light enters at the front, hits the main mirror, goes back to a small secondary and then out through the rear, which is how 500mm of focal length ends up in a barrel you could mistake for a coffee can. Inside are 7 elements in 5 groups, with a narrow 5 degree angle of view. It has no iris. The f/5.6 on the barrel is the only aperture this lens will ever give you, and the mount is plain M42, so any M42 Zenit or Praktica takes it without an adapter.

The fixed aperture shapes every picture. You get whatever depth of field the distance gives you, and you can't stop down to clean up a soft edge or pull a second subject into focus. The central obstruction costs contrast next to a refractive tele, so backlit scenes look a little milky. Then there are the rings. A heron standing in front of glittering water ends up against a field of small doughnuts, because that is how out-of-focus highlights render through a mirror. You can't switch it off. Your only control is picking a background with no bright points in it, or leaning into the effect on purpose.

The close-focus figure is the reason for the Macro label. It focuses down to 2.2 m and reaches roughly 1:4, enough to fill a good part of the frame with a dragonfly on a reed without spooking it, or to pick out one flower from the path instead of walking through the bed. That close, the light reaching the film is less than the marked f/5.6 suggests. If you meter with a handheld meter, put the magnification into Zone Light Meter and let it work out the extension factor instead of trusting the engraving. With the aperture locked, shutter speed and film speed are your only exposure controls. If sun and fast film are more than the top shutter speed can handle, an ND on that big front thread solves it.

Actually using it is the hard part. Every tremor shows at 500mm, and 1.36 kg hanging off an M42 thread strains the camera mount, so put the lens's own 1/4 inch socket on the tripod and leave the body hanging free. Focus has to be exact. On a dim Zenit screen, finding the plane of focus at f/5.6 takes patience and a steady breath. With an f/8 mirror it takes more.

Shvabe put the lens back into production in 2021 with updated coatings, still in M42, so newer copies exist alongside the older ones on the used market. A refractive 500mm f/5.6 is a much longer and heavier lens, and it would also give you an iris and smooth backgrounds. People who pick the Rubinar accept the doughnuts and the fixed aperture so they get the reach in a can-sized barrel.