Yashica Electro 35

Yashica Electro 35
image by Achim Pfennig (Image rights)

Note: the branding "Electro" was also used by Yashica on a series of 35mm SLRs. This article describes the popular rangefinder model.

Introduction

In 1966 Yashica introduced the Electro 35, the first of a very successful line of automatic exposure 35mm rangefinder cameras with fixed Yashinon lenses. A black model was also sold as the Yashica Electro 35 Professional. The rangefinder is coupled to the focusing ring and the viewfinder is parallax corrected. The front ring of the lens be used to select A for aperture priority exposure, B for bulb or a arrow symbol for flash. The shutter has a stepless automatic shutter with speeds from 30 seconds to 1/500s. Metering is with a CdS cell and done by half depressing the shutter release button. This shutter release button also has a lock and a screw-in cable release socket.

Together with its rare sister camera Yashica Electro half (introduced already in 1965) it is a milestone in exposure automation technology. It was the first implementation of an electronically controlled shutter combined with aperture priority exposure automation. In fact, without the battery the shutter would only run at its fastest speed of 1/500s and a manual selection of the shutter speed was not foreseen. Only B (bulb) and X (flash, 1/30s) could be chosen manually. However, even this speeds were controlled electronically.

When the shutter speed for the aperture selected is lower than 1/30s, the viewfinder shows an orange arrow pointing left and an orange light is displayed on the top of the camera. Similarly, when the shutter speed would have to be faster than 1/500s the viewfinder shows a right pointing arrow and there is a red control light on the top. Either situation can often be solved by changing the aperture, but anyway the shutter will still fire. With the underexposed indication on, the photographer may consider using a tripod.

Black Electro 35 Professional
image by Gerard Vogels (Image rights)

Specifications

Yashica GS with accesory kit
Lens Shade, Wide angle and Tele
auxiliary lenses, and auxiliary viewfinder
image by Pablo Coronel (Image rights)

All models of Yashica Electro are fitted with the stepless Copal ELEC electronic blade shutter, with flash sync at all speeds. The PC sync contact is placed on the left side of the camera, probably for aesthetic reasons. The Electro, G, GT, and GS models have a cold accessory shoe. The GSN and GTN models have a hot shoe.
Camera dimensions: ca. 140x90x75 mm
Weight: 750g (w/o battery and film)

All models are fitted with a Yashinon 1.7 45mm lens (a coated Gauss-type 6 elements in 4 groups high end lens) with a 55mm filter thread. On the G and later models, the lens is branded as a Color Yashinon, although it was otherwise identical. The closest focusing distance is 0.8m. The camera has three exposure modes: auto, B and flash. The first Electro has an ISO/ASA range of 15 to 500; all subsequent models have an ISO/ASA range of 25 to 1000. An ASA/DIN conversion chart is pasted to the inside of the back door.

These cameras were designed to use Mercury PX23 battery, but operate perfectly with 4SR44/357 batteries with an adaptor that can be home made, or purchased from some vendors. A [3d printable model ] has been made available in Thingiverse.

	35	35 Pro	G	GT	GS	GTN	GSN
Introduction	1966	1966	1968	1969	1970	1973	1973
Colour	chrome	black	chrome	black	chrome	black	chrome
Shoe	cold					hot
ASA	10-400		12-500	12-500 (early) 25-1000 (late)	25-1000
Meter	CdS

An accessory kit was also available from Yashica, including auxiliary lenses (1.4 tele and 0.8 wide angle), with matching auxiliary viewfinder and a lens shade, packaged in a leather pouch and included an instruction sheet [1].

Electronics

Circuit diagram of Yashica Electro 35.
See text for more explanation. (Image rights)

The electronics is the true innovation and has been developed by Yashica in cooperation with Copal. The circuit diagram from the excellent repair manual^[1] shows all relevant parts and even explains the function. The thick lines correspond to wires laid in the camera, the rest of the circuit is housed on a compact circuit board behind the CdS element. In the early version of the camera, the transistors etc. were casted in an epoxy block, which in later versions was replaced by an IC (integrated circuit) element. Central elements are highlighted in color: The complex multiple switch combined with the release button rods (yellow), the electromagnet for shutter control (green). The central capacitor's C1 (red) charging speed depends on the measured light by the CdS element (blue).
The circuit can be divided into different parts, which fulfil the required functions. In the lower right corner of the diagram the battery test circuit with extra switch and a green lamp can easily be spotted. The other parts are interconnected by the central complex multiple switch (yellow) operated by the release button. If only pressed slightly, the light meter is activated and depending on brightness (CdS R2) and chosen aperture (R9 to R16) either the yellow lamp (under-exposure, turn aperture ring left) or the red lamp (over-exposure, turn aperture ring right). If no lamp is lighted the exposure is supposed to be correct. Pressing the release button further down, not only opens the shutter by sending current to the electromagnet but also starts charging the capacitor C1 until enough light is collected by the CdS-meter. In bright light this happens in fractions of a second, in the dark this might take up to 30 seconds or more. When C1 is fully charged, the circuit withdraw the juice from the magnet, which in turn closes the shutter again. On pages 59-64 of the repair manual^[1] this is explained in more detail.
It should be noted, that you can always fire the shutter regardless of any warning lamp lighted. Also, without a battery the shutter fires at 1/500 s. One interesting feature of the circuit is, that the film speed setting is implemented in a very analogue manner using an extra aperture in front of the CdS-cell. Later electronic cameras mostly use an extra set of resistors for this purpose or combine those with the aperture resistor stack.

Electronically controlled shutters and aperture priority automatic exposure setting became very popular after the Yashica Electro 35 appeared on the market. Focus was on the hyping SLR's, though. The first of this kind would not appear before 1968, almost three years after Yashica pioneered in this field successfully.