Russian conglomerate Shvabe – makers of everything from Zenit cameras to defibrillators – is redoing its ancient line of Rubinar mirror lenses (Russian), which have experienced a recent spate of interest among old lens hunters looking for good value.
Nowadays, the question of whether or not your camera has a mirror in it refers to it having optical viewfinder versus a more modern, “mirrorless” system that uses the sensor to show a mini TV screen to the user. But years ago, a “mirror” lens referred to a telescope-like lens design that used a very wide mirror to collect lots of light, focusing it down to a central orifice that then refocused the light back to a sensor.
As seen below, the light comes in from the left and hits the back mirror (darker blue), which pushed the light to a central lens group suspended in the middle of the lens (lighter blue), which then reflects the light toward the sensor revealed in a hole in the mirror and represented by the red x.
The great charm of these lenses was that they were quite cheap to make, yet they were able to collect lots of light, perhaps at the expense of an inconvenient size. Despite this, most were relatively slow lenses, and they tended to have a cheap reputation. That said, many photographers loved them for their dreamy backgrounds and frogs egg bokeh patterns, as seen on this Flickr collection.
The Rubinar lenses are some of the best-liked versions of these. They mostly came in the M42 mount system started during World War II as Zeiss was producing lenses for the Nazi war machine, and which later became a common mount system for telescopes following the war.
The new versions will come in 300 f/4.5, 500 f/5.6, 500 f/8 and 1,000mm f/10, reflecting past configurations. The new lenses are pictured below.
Details about image quality and specifications have not yet been published. The older lenses MTF charts showed a lot to be desired, as can be seen in the Mid-20th-Century MTF chart below (Russian). It will be interesting to see what modern coatings might be able to do for quelling image quality problems that often appeared in the old lenses to be related to issues coatings are known to help; such as ghosting and light loss through multiple elements.