LZOS MTO-11CA 1000mm f/10 (mirror)

Two and a half degrees. That is the entire slice of the world the MTO-11CA takes in, and it asks you to carry about 1.95 kg and roughly 238 mm of barrel for the privilege. Bolted to a Zenit, the lens outweighs the camera by a long way and the whole rig wants to tip nose down. You do not swing it around chasing things. You level a tripod, find the subject in a finder that suddenly feels like a keyhole, and wait for the air to settle.

LZOS built it at Lytkarino, the optical glass plant that also made the Rubinar mirror lenses, and it follows the Maksutov tele-optic pattern: a thick meniscus corrector at the front, mirrors folding the light back on itself, and a hood recessed into the barrel instead of screwed onto it. That fold is how a thousand millimetres fits in a tube a fraction of the length of a refractive 1000mm. The price of the trick is the aperture. There is no iris at all. Every exposure is made at f/10, and the only ways to change how much light reaches the film are the shutter and a filter.

On film the pictures look like catadioptric pictures. Contrast sits below what a good refractive telephoto gives, and with a bright sky in or near the frame a faint veil can creep over the shadows. Most of the light bending is done by mirrors, which do not disperse colour, so fringing is much milder than on a refractive lens of this length. The secondary mirror blocks the middle of the light cone, which is why out-of-focus highlights render as rings; foliage or glinting water behind a subject can turn into a field of small doughnuts. Over a kilometre of warm air, shimmer and haze usually cost more sharpness than the optics do.

The M42 thread puts it straight onto Zenit and other M42 bodies, and onto mirrorless cameras and SLR systems with a shorter flange distance through an adapter. Its most rewarding subject is the moon. At this focal length the full moon lands on a 35mm frame roughly 9 mm across, about a quarter of the long side, big enough to show the maria clearly without cropping. The real limitation is that fixed aperture. You cannot stop down to buy depth of field on a distant subject, and f/10 gives a dim finder image, so focusing on a plain ground glass in shade is slow work. Handholding is out; even a light tripod head will show shake at 1000mm.

Exposure is simpler than it looks, since one of the variables is nailed down. In Zone Light Meter, set the aperture to f/10 and let the app solve for shutter speed; if you thread on an ND to slow the shutter or to tame bright snow, enter its filter factor so the reading allows for it. Filters are the awkward part. This is one of only two Soviet lenses reported to take 116mm filters across the full aperture, yet published figures for the front size disagree, so measure your own copy before ordering glass that big.

The obvious lens to compare it with is the Rubinar 10/1000 from the same plant, the other Soviet lens reported to take those 116mm filters. The MTO-11CA costs far less than a refractive 1000mm usually does. What the saving costs you is control. You get one f-stop, and a lens that only behaves when the tripod and the weather both cooperate.