SLR made in Japan? The illustrious Asahiflex, proud precursor of the prestigious Pentax." pp. 25, 30. Popular Photography, Volume 66 Number 1; January 2002. Wade, Collector's Guide. pp. 142–143 From 1952 to 1983, Asahi Optical (today called Pentax and owned by Ricoh) manufactured cameras exclusively of SLR type and has made them in the greatest variety of formats of any modern camera company – from 110 to 6×7 film, and today's digital. 1953 VEB Zeiss Ikon (Dresden) Contax E (East Germany): first built-in light meter SLR. Had an external selenium photoelectric cell mounted behind a door on the pentaprism housing, above the lens. The meter was uncoupled – the photographer would need to wait until the meter stabilized and manually set the shutter speed and lens aperture to match the indicated exposure reading. The first camera with a built-in meter (also uncoupled) was the Zeiss Ikon Contaflex (Germany) 35 mm twin-lens reflex (TLR) camera of 1935.Wade, Collector's Guide. pp. 23–24, 54 1953 Zeiss Ikon Contaflex I (West Germany): first leaf shutter 35 mm SLR. Had Synchro-Compur leaf shutter and front cell focusing 45mm f/2.8 Tessar lens,Matanle, pp. 193–194Wade, Collector's Guide. pp. 40–41 built-in selenium-coupled exposure meter. For many years, reliable focal-plane shutters were very expensive and SLRs equipped with Compur or Prontor leaf shutters were strong competitors.Small and Barringer, pp. 50–60, 160 As FP shutters improved, their faster available speeds won out in the late 1960s and leaf shutter 35 mm SLRs disappeared around 1976.Lea, "Mamiya 528 AL" p. 139 1953 Metz/Kilfitt Mecaflex (West Germany): first (and only) square format 35 mm SLR. Took up to fifty exposures of 24×24 mm frames on 135 film. A compact Prontor leaf shutter design with bayonet mount interchangeable lenses.Wade, Collector's Guide. pp. 44–47 135 film's standard 24×36 mm frame size is inefficient. Its 3:2 aspect ratio is too wide, recording only 59% of a required 43.3 mm diameter lens image circle. This makes lenses for the format overly large for the image area. A square 24×24 mm frame maximizes coverage at 64% of a smaller 33.9 mm image circle. The Mecaflex's designer, Heinz Kilfitt, also designed the Robot (Germany) of 1934, the first 24×24 mm 35 mm (not 135 type) camera. Both failed to disturb the entrenched rectangular format and the 3:2 ratio still dominates digital SLRs. Olympus' Four-Thirds System digital format of 2002 is the latest attempt at a narrower, albeit not