The Zenit 3 is a 35mm film SLR camera manufactured by Krasnogorsky Mekhanichesky Zavod (KMZ: 'Mechanical Factory of Krasnogorsk') in Moscow, between 1960-62, quantity 81776 copies. Zenit (Зенит = Зенит), means Zenith, a point in the sky that appears directly above the observer. 'Zenit 3' is engraved in Cyrillic script on the front of the prism housing.
The Zenit-3 is the third model of the Zenit brand, the successor to the Zenit (1953-56) and Zenit S (1955-61). The main differences between them are an added self-timer and a shutter cocking lever instead of a knob.
Early models of the Zenit cameras were based on the Zorki rangefinder camera (a copy of the Leica II). In transforming the Zorki into an SLR, the simplest approach was taken: the rangefinder housing was removed from the top and replaced by a ground-glass screen and prism; a mirror was added below, and the M39 thread mount was pushed forward to make room for the mirror inside.
During the first years of production, until the Zenit E of 1967, Zenit camera development coincided with that of the Zorki cameras.
The Zenit 3 shows outstanding workmanship; compared, for example, to the Zenit 3M the top-plate controls are small and elegant. The camera is very solid and was apparently expensive to make. This explains why it was in production for only two years. As any early Zenit it is quite uncommon now.
- Lens: Industar-50 50mm f/3.5
- The camera may also be seen with the bigger Helios-44 (ГЕЛИОС) 58mm f/2, or even the Industar-22 50mm f/3.5.
- KMZ's 39mm screw mount 
- Focusing: fixed pentaprism with plain ground-glass screen
- Shutter: rubberized silk double cloth curtain, horizontal-travel
- Speeds: 1/30-1/500 +B, dial on the top plate 
- Cocking lever: also winds the film, right hand, short stroke, retractable
- Shutter release: on the top plate, beside the winding knob; with threaded cable release socket
- Frame counter: coupled with winding lever, beneath it
- Mirror: not instant return
- Re-winding knob: on the left of the top plate; incorporates film-type reminder dial
- Re-wind release: turn (and depress) the collar around the shutter release, Д rewind, П wind
- Self-timer: lever on the front of the body, and 'start' button above this (Zorki-6 type). The self-timer releases the mirror and shutter at the same time (whereas the one on the Zenit 3M releases the mirror a fraction of a second before to lessen camera shake)
- Flash PC socket: on the front of the top-plate, only activates at 1/30 speed
- Synch timing advance, from 0 to 25 ms, adjustable by a lever and scale beneath the speed dial
- Bottom plate opening: by a pop-up key; .
- A half-turn of the key unfastens the bottom plate. Engravings around the key: ЗAКР - ОTKP (Zakr- Otkr = Close - Open). ОTKP is an abbreviation for ОТКРЫТЫЙ
- Film loading: bottom loading, w/ special removable take up spool; film should be cut with a 100mm leader.
- Other details: Tripod socket 3/8 inch; Strap lugs
- Serial no. on the back side of the top plate, first two digits show the production year
- Body: metal; Weight: 840g
- S = C in cyrillic
- According to Alexander Komarov Fotoua. You can also find serial numbers for dating of the cameras in this site
- There is another classification by Aidas Pikiotas at 
- Suglob, Shaternik & Kochergin (2009) 1200 Cameras from the USSR. Mirfoto, 2009 ()
- Discussion of camera classifications in the books of Princelle and Suglob, Shaternik & Kochergin in USSR Photo Forum
- It looks like M39 Leica mount but due to the mirror space, the rangefinder M39 mount lenses do not work properly on this camera. You can use them only the close-up focus range.
- Shutter speed can be selected before or after the shutter is cocked, contrary to early Leica-inspired cameras of the Soviet Union.
- Princelle, Jean Loup (2004), The Authentic Guide to Russian and Soviet Cameras ('Made in USSR'), Le Reve Edition. ISBN 2952252106; or the earlier edition: Hove Foto Books, 2nd edition, 1995. 200 pages. ISBN 1874031630. Paperback.