Zuiko

Zuiko is a brand of optical lenses made by Olympus Corporation that was used up to and into the Four Thirds system era. The name Zuiko means 'Holy Light', using a character from the Mizuho Optic Research Laboratory, where the lens was developed, and a character from Takachiho Corporation, which would eventually become the Olympus Corporation.
With the introduction of the Micro Four Thirds system in 2008, new lenses for that system started to be branded as M.Zuiko Digital.

Optical formula nomenclature

For lenses manufactured until approximately 1972, the number of optical elements of the lens, angle of view, and diaphragm operation could be distinguished by the markings engraved on the lens. The engraving dropped the number of elements with the advent of multicoating, which occurred during the production of OM system lenses. Ace, Pen-F, FTL, and early OM system lenses carry the letter prefix denoting the number of optical elements. Later OM system lenses omitted this prefix.

Prefix	# of elements	Optics	Aperture diaphragm	Angle of view
A.	1	Zuiko	Auto-	W
B.	2	Zuiko	Auto-	W
C.	3	Zuiko	Auto-	W
D.	4	Zuiko	Auto-	W
E.	5	Zuiko	Auto-	S
F.	6	Zuiko	Auto-	S
G.	7	Zuiko	none	S
H.	8	Zuiko	none	S
I.	9	Zuiko	none	T
J.	10	Zuiko	none	T
K.	11	Zuiko	none	T
L.	12	Zuiko	none	T

;Notes
For example, an "Olympus OM-SYSTEM G.Zuiko Auto-S 1:1.4 f=50mm" is a lens with a 'Standard' focal length and a maximum aperture of 1.4 featuring a seven-element construction and an automatic diaphragm, built for the OM-system. The use of 'standard' refers to the focal length compared to the diagonal dimension of the imager; in this case 50mm is approximately the diagonal dimension of the 35mm film frame. 'Wide-angle' lenses have focal length significantly shorter than the diagonal dimension, while 'Telephoto' lenses have focal length significantly greater than the diagonal dimension.

Fixed-lens cameras

Medium format cameras

The first 'Zuiko'-branded lens was a 75mm 4.5 lens fitted to the Semi-Olympus I of 1936. The Semi-Olympus used a Semi-Proud body, which took pictures in the 6×4.5 frame using medium format film.
The Olympus Flex I was a twin-lens reflex camera first sold in 1952.

Early 35mm cameras

In 1948, Olympus marketed the first 35mm camera in Japan, the Olympus 35 I. It was a viewfinder camera using a 24×32mm frame size fitted with a fixed 'Zuiko Coated' 40mm 3.5 lens; that same lens was also used on the subsequent 35 III, IV, and V. Starting with the IV series, the lens dropped 'Coated' in favor of 'F.C.', in both cases referring to the anti-reflective coating.
Using a chassis similar to the 35 V, Olympus also released the Olympus Wide in 1955, a viewfinder camera featuring the D.Zuiko-W 35mm 3.5 wide-angle lens. A version of the Wide using the same lens was produced in 1957 with an integral uncoupled meter, branded the Wide-E. The Wide-E was sold in the United States as the Sears Tower 54. In 1958, the Wide II viewfinder camera replaced the Wide with no change to the lens.
Olympus also began selling the Olympus 35 S rangefinder in 1955, alongside the Olympus 35 Vb viewfinder which had been launched that same year. The initial version of the 35 S used the same 'normal' lens as the preceding viewfinder cameras, now branded D.Zuiko 1:3.5 f=4.0 cm, but Olympus quickly released versions of the same body with faster non-interchangeable lenses, including an E.Zuiko 48mm 2.8 and a G.Zuiko 45mm 1.9. The slowest 35 S with the 40mm 3.5 lens was replaced by the 35 K in 1957. The 35 K was also sold by Sears as the Tower 56.
The first Olympus 35mm rangefinder camera with a wide-angle lens was the Wide-S of 1957. Lens speed was increased by almost two stops compared to the Wide and Wide-E with the H.Zuiko-W 35mm 2.0 fitted to the Wide-S. The Wide-S was also sold by Sears as the Tower 20.
The Olympus 35 S-II replaced the 35 S in 1957 using a body similar to the Wide-S with a choice of two lenses, a faster G.Zuiko 42mm 1.8 and a slower E.Zuiko 48mm 2.8 carried over from the 35 S. The faster lens was later replaced by a Zuiko 42mm 2.0. The 35 S-II was also marketed in the United States by Sears as the Tower 10 and the Tower 18.

Automated exposure 35mm cameras

Olympus released the Olympus-Auto electro-set and Auto-B electro-set shortly after the Ace interchangeable lens rangefinder, using styling largely borrowed from the Ace. Both of the Auto models had built-in exposure meters, and were distinguished by lens speed; the older Auto had the faster G.Zuiko 42mm 1.8 lens carried over from the 35 S-II and the Auto-B had a slower E.Zuiko 42mm 2.8 lens. Cosmetically, the Auto had a cover for the meter window, which was omitted on the Auto-B. The 'electro-set' designates the semi-automated exposure system; by setting the film speed on the camera body, match-needle metering is used to set aperture and shutter speed simultaneously. The aperture and shutter speed settings are coaxial with the lens and are geared to turn together when the shutter speed is changed; the aperture may be varied, but the shutter speed will change with aperture to maintain exposure. The Auto Eye of 1960 succeeded the older electro-set models and added full shutter-priority autoexposure using a non-interchangeable version of the D.Zuiko 45mm 2.8 from the Ace. The camera will not release the shutter if the correct exposure cannot be set based on the selected shutter speed. A slightly faster D.Zuiko 43mm 2.5 was used for its successor, the Auto Eye II, released in 1962.
Also in 1962, Olympus released the S Electro Set, which used the G.Zuiko 42mm 1.8 lens from the original Auto. An updated version designated SC was released in 1963; it retained the 'Olympus-S' top plate engraving using the same lens but switched the meter technology from selenium cell to cadmium sulfide. The successor of the Olympus-S twins was the first of the two-letter 35 xx models, released in 1965; the Olympus 35 LE used a slightly faster G.Zuiko 42mm 1.7 lens with similar double Gauss optical construction and prominently advertised the use of six transistors. A similarly styled 35 LC using the same lens was released in 1967, which dropped the autoexposure functions of the 35 LE. Like the older electro-set models, the 35 LC coupled the shutter speed and aperture rings so that once the exposure was set, changing the shutter speed would also automatically change the aperture.
Between 1968 and 1983, Olympus sold the Trip 35 camera. It was a scale/zone-focused camera based on the Pen EES which featured a D.Zuiko 40mm 2.8 Tessar-type lens, two automatically selected shutter speeds for aperture-priority autoexposure, or programmed autoexposure driven by the selenium cell meter. No batteries were required. It was marketed as a kit with a compact flash.
The 35 LE/LC were followed by the flagship fixed-lens 35 SP rangefinder of 1969, again using the G.Zuiko 42mm 1.7 lens. The 35 SP featured both manual and programmed automatic exposure modes, where the meter reading automatically set both aperture and shutter speed. A switch on the back of the 35 SP engaged the spot meter to override the default scene-average metering. An updated 35 SPN added a battery check in 1972, but otherwise kept the same features and lens as the 35 SP. The camera was restyled and was re-released as the 35 UC in 1973.
Meanwhile, Olympus released the 35 EC economy fixed-lens camera alongside the 35 SP in 1969; compared to the SP, the EC had a slower E.Zuiko 42mm 2.8 lens carried over from the Auto-B of 1959, but was also markedly smaller and lighter. The 35 EC offered programmed automatic exposure only and had no rangefinder. The 35 EC was replaced in 1971 by the 35 EC2, which added a battery check function. The updated 35 ECR of 1972 added a rangefinder to the 35 EC2 but again was limited to programmed autoexposure. In 1974, Olympus released the 35 ED, last of the 'economy' line, equipped with a slightly wider D.Zuiko 38mm 2.8 lens, rangefinder focusing, and programmed autoexposure only.
In 1970, Olympus marketed the 35 RC as a mid-range compromise; although it was approximately the same size as the 35 EC using the same E.Zuiko 42mm 2.8 lens, the 35 RC added more advanced features from the 35 SP including true rangefinder focusing and the option of either shutter-priority autoexposure or manual exposure control. The 35 DC of 1971 also offered rangefinder focusing of a faster F.Zuiko 40mm 1.7 lens, but was limited to programmed autoexposure only. The 35 DC was equipped with a backlight exposure compensation to increase exposure by 1.5 stops by depressing a button, a simpler solution than the spot meter of the 35 SP. Finally, in 1975, Olympus released the 35 RD, combining the faster F.Zuiko 40mm 1.7 lens from the 35 DC with the shutter-priority autoexposure or manual exposure controls of the older 35 RC. However, the 35 RD omitted the backlight compensation button of the 35 DC.