and auto-diaphragm design with excellent interchangeable lenses and huge accessory system. Although the F was not technologically ground-breaking, it sold 862,600 units and made the 35 mm SLR the dominant professional miniature format camera (displacing the 35 mm RF) by the early 1960s.Dan Richards, "F Is For Family Tree," p. 67. Popular Photography & Imaging, Volume 68 Number 11; November 2004. The perfection of the optical and mechanical formulae of the interchangeable lens SLR in the one-two punch of the Hasselblad 500C (see above) and Nikon F also ended the popularity of the medium format twin-lens reflex (TLR) camera (typified by the Franke & Heidecke Rolleiflex/Rolleicord series [Germany, later West Germany]) by the early 1960s.Jason Schneider, "The Camera Collector: A farewell to the twin-lens Rolleiflex: elegant to the end. It never switched lenses or lowered its patrician standards." pp. 82, 86, 92–93, 136. Modern Photography, Volume 47, Number 11; November 1983. The F's improved successor, the Nikon F2 (Japan) of 1971, is widely regarded as the finest mechanically controlled 35 mm SLR camera ever made. 1959 Voigtländer–Zoomar 1:2.8 f=36mm–82mm (USA/West Germany): first zoom lens for 35 mm still cameras.Ray, pp. 172–173 Designed by Zoomar in USA and manufactured by Kilfitt in West Germany for Voigtländer. Originally mounted for Voigtländer Bessamatic series (West Germany) 35 mm leaf shutter SLRs, but later available in Exakta and other mounts.Kingslake, pp. 173–174 Zoom lenses and SLR film cameras are perfect for each other, because an SLR always shows what the lens is imaging during zooming, something difficult, if not impossible, to do with other optical viewfinder systems.Kraszna-Krausz, pp. 1698–1699 1960s 1960 Konica F (Japan): first SLR with 1/2000 second and 1/125 second flash X-synchronization focal-plane shutter.Lea, p. 121 Modern focal-plane shutters are dual curtain traveling slit shutters.Horder, p. 174Langford, Basic Photography. Third Edition. p. 109 They provide faster shutter speeds by timing the second shutter curtain to close sooner after the first curtain opens and narrowing the slit "wiping" the exposure on the film, instead of moving the curtains faster across film gate,Langford, Basic Photography. Third Edition. pp. 109–110 because they are too fragile to survive the necessary accelerative shocks. Long wipe times can cause cartoonish distortion of very fast moving objects instead of truly freezing their motion.Horder, p. 175Langford, Basic Photography. Third Edition. pp. 109–111 (The use of leaning in illustration to give the impression of speed is a caricature of the distortion