The 490mm f/6.2 OR-451M (spelled OP-451M in Cyrillic) lens comes from an obsolete copy machine that was in use back in the USSR. Now these lenses find no use anywhere and are dirt cheap. They go for no more then $100 on e-bay and can be got as cheap as $20 locally, in the ex-USSR countries.

The OR-451M has 6 separate elements. It's perfectly symmetrical and is optimized for 1:1 reproduction work. At 2.2 kg (~4.84 lbs) it's not too heavy for its focal length and speed but rather bulky, 5" in diameter (just fine on a 6x6" lens board but hardly mountable on anything smaller). The barrel has no aperture scale as the aperture was originally operated through the copy machine itself, from outside of the lens. So LF users have to calibrate their aperture scales themselves.

http://lens-club.ru/public/files/opt...0e9765def8.gif
http://www.photohistory.ru/Pictures-1/Lens-OR-451-f.jpg
http://lens-club.ru/public/files/img...a5c2e0fe16.jpg

I bought the OR-451M out of pure curiosity and tested it and was really surprised by the out of focus background rendition of this purely technical copy lens.... In the center it was no worse than the background blur of my 480mm Dagor, with beautiful OOF at all apertures including wide open (while Dagors make great defocused backgrounds only at f/10 and smaller f-stops). And that's at no more than a 1/10 of the Dagor's price.

Well, no it is not equal to a Dagor in any other respects. It's a narrow angle lens covering just about 42° at small f-stops (15"/38cm field diagonal at infinity), and illuminates about 50° (18"/45cm at infinity) with the unsharp edges included.

It also shows a lot of coma that spoils both sharpness and out of focus rendition off center so I'd better stop it down well when using the OR-451M on 8x10". (At 1:1 coma is absent in any symmetrical lens so no special correction means are needed. But the closer to infinity the subject is, the more prominent coma becomes in a lens like this.) But on 4x5" the glass is fine at all apertures. It's somewhat on the soft side from wide open to f/10; the softness is gone at f/11. No I don't mean it's really soft focus; I compared the OR-451M to my 300mm f/4.5 Ross Express at wide apertures on 4x5" and found their pictures to look very similar. Though I actually liked the OR-451M more.

For a 490mm f/6.2, it's CHEAP. And at least it's quite a lot of fun. So I'd like to welcome everybody to buy and try the beasts - before they are all gone to the trash.... as nowadays nobody is interested in them.

P.S.: There also were the OR-451 (without the "M" in the name) that most probably was exactly the same glass in a somewhat different barrel and the OR-452 of the same type but of a different focal length that should probably also be a similar performer. But sorry I have no personal experience with those.