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Finding information about the manufacturers of Soviet-Russian exposure meters isn't a very faithful task. In the Soviet Union they were seen more as supportive to the unified Soviet facade than as separate economic entities. Also, the usual sources of information all remain mute on the subject. Princelle simply says that it's outside the scope of his book. The others don't treat it as a field either. So, all I have to work on in this review of the Leningrad-7 is my direct experience.
The Leningrad-7 is the 1980's incarnation of the postwar Leningrad line of amateur-grade light meters. Manufactured by "Vibrator" of Leningrad (as testified by the "V" logo in a triangle), it was succeeded by the very similar Leningrad-8. I don't know much about production dates and numbers, but a rough dating is provided by the stamp in my Leningrad-7's case, which reads 5 March 1982. The Leningrad-7 is coded Yu-101 in factory documentation and on the back of the meter itself; the Leningrad-8's alter ego is the Yu-102. I have no information about further continuation of the Leningrad series, but given the times, I don't think it's likely.
The Leningrad-7 is a selenium-based light meter. That's both good and bad. Good because it uses the photo-electric effect for power and for that reason doesn't need batteries; bad because selenium ages, making the meter progressively more irreliable. The calculator dial displays speeds between 1/2000s and 30s, and aperture values between f/1.4 and f/22. The film speed can be set in GOST and DIN. No provisions are made for cinematic use.
The light meter works with the Exposure Value (EV) system, that assigns numbers to light intensity. For example, EV 1 means 1 s at f/1.4 with 100 ASA film, but it can also mean 30 s at f/8. The EV system basically takes advantage of the inverse relationship between aperture and shutter speed, and follows the pseudomathematical formula EV = S/F (S is shutter speed, F is aperture). The Leningrad-7 measures the intensity of the light in EV values, and the photographer can then shift around with shutter speed and aperture, within the given EV value, to obtain an acceptable combination.
The Leningrad-7 is a bit complicated when it comes to its operation. It has two separate readout scales, and an internal flip-up sunscreen that can be engaged to moderate the light that reaches the cells. It took me a long time to figure out how it all leaves together. Some people have told me that this Leningrad is operationally very similar to a certain Gossen light meter (the Sixtomat I think), but as I didn't own one, that didn't help me much. Eventually I got to the bottom of it though.
The Leningrad has three readout scales and three modes of operation. The first scale displays EV values from 1 to 5, the second from 5 to 12, the third from 12 to 18. You can switch scales by either setting the lever on the left to the top or to the bottom – intermittent positions are invalid. If the lever is set to the top, the low scale takes over, and the light meter is very sensitive. (This works because as you move the lever, the cells internally slide forward towards the window, giving the meter less of a tunnel view.) If you move the lever all the way down, the cells slide back into the light meter, and you have two choices. Either you use the light meter as-is, in which case you meter values in the scale from EV 5 to 12, or you flip up the in-built sunscreen, which engages the third scale and limits the meter's sensitivity between EV 12 and 18. Complicated, isn't it?
The Leningrad-7 comes with a milk glass that fits over the cells, to give it direct-light metering capability. Without the glass, it is suited for indirect metering. The difference is that with direct metering, you point the light meter at the light source instead of the subject, to obtain a direct value for light intensity. This prevents gloss or absorption in the subject from influencing the readout. Indirect metering works opposite, literally: you point the meter at the subject to gauge the intensity of the reflecting light. Both methods have their pros and cons.
This would have been a nice piece of equipment to have around if your only camera was a lightmeterless Zorki. To western standards it isn't especially well-made or reliable, and would fall in the crowded category of cheap selenium light meters. It does its job, and it could be a lifesaver, but it's not exceptional, or even above normal. Verdict: average piece of Soviet auxiliary equipment.