Contax RTS

35mm MF film SLR camera


Production details
System: Contax/Yashica (1975)
Imaging plane
Maximum format:35mm full frame
Mount and Flange focal distance:Contax/Yashica [45.5mm]
Imaging plane:36 × 24mm film
Model:Electronically controlled
Speeds:4 - 1/2000 + B
Exposure metering:Through-the-lens (TTL)
Exposure modes:Aperture-priority Auto
Physical characteristics

Manufacturer description

Lens Mount: Contax/Yashica Mount (three-claw bayonet mount) developed by mutual cooperation of Carl Zeiss, West Germany, and Yashica, Japan.

Lens: PLANAR T* f/1.4 50mm standard lens composed of 7 elements in 6 groups, interchangeable with a wide range of high performance Carl Zeiss lenses

Shutter: Electronic focal plane shutterof a unique design (primary and secondary shutter curtains uncap to provide starting from the identical position) • Electronic timing on both Auto and Manual • Shutter speeds continuously variable from LT (4 sec.) to 1/2000 sec. on Auto; 14 clickstop settings from 4 to 1/2000 sec. and B on Manual • X sync terminal

Shutter Release: Feather-touch magnetic release • Release socket for cable switch and off-hand controls

Exposure Control: Through-the-lens automatic exposure control with SPD sensor above the viewfinder eyepiece taking center-weighted light reading • Fully automatic exposure through lens aperture preselection (exposure readout on manual operation) • LED shutter speed display in viewfinder • EV range from EV -1 to 19 (F1.4 at ASA 100) • ASA range from 12 to 3200 • Provision for exposure compensation (scale calibrated from x4 to 1/4; in between settings feasible) • Operates on 6V silver oxide or alkaline battery (Eveready 544, Ucar 544, Mallory PX28, Alkaline Eveready 537 or equivalent)

Viewfinder: Through-the-lens reflex viewfinder shows up to 92% of the actual picture area • Magnification ratio: 0.87X • Pentaprism silver coated and deflection mirror multi-layer coated to ensure maximum brightness of the viewfinder field • Focusing screen interchangeable from the lens mount side

Viewfinder Display: 16-dot LED shutter speed display shows calibrated and in-between speeds • Green shutter speed pointer overlaps "A" setting on Auto and indicates shutter control dial setting on manual • Aperture display shows maximum aperture of the lens in use on the extreme right and f-stop in use in green figure • Exposure compensation tab appears when the exposure compensation pointer is set at any position other than "X1"

Film Advance: Film advance lever advances film through a single 140 degree stroke or several short ratchet action • Exposure counter resets automatically to start position when the back cover is opened

Film Rewind: Film rewind crank-handle with unique clutch action • White line on top of the knob rotates to indicate proper film advance

Camera back: Back cover opens when the film rewind knob is pulled all the way out • Camera back interchangeable with Data Back or 250 Film Back (for use with motor drive unit)

Other Features: Multiple exposure through depression of the film rewind release button • Mirror lock lever • LED battery checker display • Depth-of-field preview button • Direct X contact shoe with anti-shock provision • Motor drive coupling terminal and film advance coupler


The CONTAX RTS is a highly advanced electronic SLR system camera developed by mutual cooperation of Carl Zeiss, West Germany, and Yashica, Japan. It offers the advantage of the most sophisticated fully automatic through-the-lens exposure control. Designed under the theme of "Real Time" functional response and disposition of information, it provides such capability in alI fields of photography as could not possibility be expected of other 35mm SLR models. The New Bayonet Mount also a product of mutual cooperation between Carl Zeiss and Yashica - affords perfect coordination of the optical, mechanical and electronic systems. The exclusive "Real Time" features are:

1. "Real Time" LED Shutter Speed Display

By pressing the LED display button before or after film wind, the LED (light emitting diode) in the viewfinder will come on instantly to display the calibrated or in-between shutter speed ensuring correct exposure in relation with the preselected aperture.

2. "Real Time" Magnetic Release

Because this magnetic release trips the shutter through feather-touch fingertip action, camera shake at the critical moment of exposure is effectively prevented. Since, moreover, shutter tripping is accomplished through contact of an electric switch, all types of off-hand controls can be used directly. Correct exposure is obtained through "Real Time" light reading immediately before exposure.

3. "Real Time" 1/2000 sec. Maximum Shutter Speed

Because your CONTAX RTS features an electronic focal plane shutter with a unique design under which the primary and secondary curtains uncap to provide starting from the same position, precise shutter speeds can be obtained up to the maximum of 1/2000 sec.

4. "Real Time" Off-Hand Controls

Because the magnetic release functions strictly on electrical principle, various types of electrically operated off-hand controls can be used directly by merely plugging into the camera's release socket. The off-hand controls currently available include the Infrared Controller Set and Interval Timer.

5. "Real Time" Motor Drive System

The magnetic release does greatly more than just tripping the shutter. In the final stage of its function, it switches on the motor drive switch to provide precise synchronization with the motor drive unit. Of the two types of motor drive units, the Real Time Winder is a compact unit which can be regarded as standard equipment of your CONTAX RTS.

6. "Real Time" T* (T-Star) Carl Zeiss Lenses

The high performance and extra-high speed design of the Carl Zeiss lenses, featuring the T* (T-Star) multi-layer anti-reflection coating which minimizes harmful glass-to-air reflections and assures "Real Time" color reproduction and contrast permit the photographer to select comparatively high shutter speed even in subdued light situations, thus offering new possibilities in "Real Time" photography.

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35mm full frame

43.27 24 36
  • Dimensions: 36 × 24mm
  • Aspect ratio: 3:2
  • Diagonal: 43.27mm
  • Area: 864mm2

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Image stabilizer

A technology used for reducing or even eliminating the effects of camera shake. Gyro sensors inside the lens detect camera shake and pass the data to a microcomputer. Then an image stabilization group of elements controlled by the microcomputer moves inside the lens and compensates camera shake in order to keep the image static on the imaging sensor or film.

The technology allows to increase the shutter speed by several stops and shoot handheld in such lighting conditions and at such focal lengths where without image stabilizer you have to use tripod, decrease the shutter speed and/or increase the ISO setting which can lead to blurry and noisy images.

Original name

Lens name as indicated on the lens barrel (usually on the front ring). With lenses from film era, may vary slightly from batch to batch.


Format refers to the shape and size of film or image sensor.

35mm is the common name of the 36x24mm film format or image sensor format. It has an aspect ratio of 3:2, and a diagonal measurement of approximately 43mm. The name originates with the total width of the 135 film which was the primary medium of the format prior to the invention of the full frame digital SLR. Historically the 35mm format was sometimes called small format to distinguish it from the medium and large formats.

APS-C is an image sensor format approximately equivalent in size to the film negatives of 25.1x16.7mm with an aspect ratio of 3:2.

Medium format is a film format or image sensor format larger than 36x24mm (35mm) but smaller than 4x5in (large format).

Angle of view

Angle of view describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.

As the focal length changes, the angle of view also changes. The shorter the focal length (eg 18mm), the wider the angle of view. Conversely, the longer the focal length (eg 55mm), the smaller the angle of view.

A camera's angle of view depends not only on the lens, but also on the sensor. Imaging sensors are sometimes smaller than 35mm film frame, and this causes the lens to have a narrower angle of view than with 35mm film, by a certain factor for each sensor (called the crop factor).

This website does not use the angles of view provided by lens manufacturers, but calculates them automatically by the following formula: 114.6 * arctan (21.622 / CF * FL),


CF – crop-factor of a sensor,
FL – focal length of a lens.


A lens mount is an interface — mechanical and often also electrical — between a camera body and a lens.

A lens mount may be a screw-threaded type, a bayonet-type, or a breech-lock type. Modern camera lens mounts are of the bayonet type, because the bayonet mechanism precisely aligns mechanical and electrical features between lens and body, unlike screw-threaded mounts.

Lens mounts of competing manufacturers (Canon, Nikon, Pentax, Sony etc.) are always incompatible. In addition to the mechanical and electrical interface variations, the flange focal distance can also be different.

The flange focal distance (FFD) is the distance from the mechanical rear end surface of the lens mount to the focal plane.

Lens construction

Lens construction – a specific arrangement of elements and groups that make up the optical design, including type and size of elements, type of used materials etc.

Element - an individual piece of glass which makes up one component of a photographic lens. Photographic lenses are nearly always built up of multiple such elements.

Group – a cemented together pieces of glass which form a single unit or an individual piece of glass. The advantage is that there is no glass-air surfaces between cemented together pieces of glass, which reduces reflections.

Focal length

The focal length is the factor that determines the size of the image reproduced on the focal plane, picture angle which covers the area of the subject to be photographed, depth of field, etc.


The largest opening or stop at which a lens can be used is referred to as the speed of the lens. The larger the maximum aperture is, the faster the lens is considered to be. Lenses that offer a large maximum aperture are commonly referred to as fast lenses, and lenses with smaller maximum aperture are regarded as slow.

In low-light situations, having a wider maximum aperture means that you can shoot at a faster shutter speed or work at a lower ISO, or both.

Closest focusing distance

The minimum distance from the focal plane (film or sensor) to the subject where the lens is still able to focus.

Closest working distance

The distance from the front edge of the lens to the subject at the maximum magnification.

Magnification ratio

Determines how large the subject will appear in the final image. For example, a magnification ratio of 1:1 means that the image of the subject formed on the film or sensor will be the same size as the subject in real life. For this reason, a 1:1 ratio is often called "life-size".

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Manual focus override in autofocus mode

Allows to perform final focusing manually after the camera has locked the focus automatically. Note that you don't have to switch camera and/or lens to manual focus mode.

Electronic manual focus override is performed in the following way: half-press the shutter button, wait until the camera has finished the autofocusing and then focus manually without releasing the shutter button using the focusing ring.

Manual diaphragm

The diaphragm must be stopped down manually by rotating the detent aperture ring.

Preset diaphragm

The lens has two rings, one is for pre-setting, while the other is for normal diaphragm adjustment. The first ring must be set at the desired aperture, the second ring then should be fully opened for focusing, and turned back for stop down to the pre-set value.

Semi-automatic diaphragm

The lens features spring mechanism in the diaphragm, triggered by the shutter release, which stops down the diaphragm to the pre-set value. The spring needs to be reset manually after each exposure to re-open diaphragm to its maximum value.

Automatic diaphragm

The camera automatically closes the diaphragm down during the shutter operation. On completion of the exposure, the diaphragm re-opens to its maximum value.

Fixed diaphragm

The aperture setting is fixed at F/ on this lens, and cannot be adjusted.

Number of blades

As a general rule, the more blades that are used to create the aperture opening in the lens, the rounder the out-of-focus highlights will be.

Some lenses are designed with curved diaphragm blades, so the roundness of the aperture comes not from the number of blades, but from their shape. However, the fewer blades the diaphragm has, the more difficult it is to form a circle, regardless of rounded edges.

At maximum aperture, the opening will be circular regardless of the number of blades.


Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

Maximum diameter x Length

Excluding case or pouch, caps and other detachable accessories (lens hood, close-up adapter, tripod adapter etc.).

For lenses with collapsible design, the length is indicated for the working (retracted) state.

Weather sealing

A rubber material which is inserted in between each externally exposed part (manual focus and zoom rings, buttons, switch panels etc.) to ensure it is properly sealed against dust and moisture.

Lenses that accept front mounted filters typically do not have gaskets behind the filter mount. It is recommended to use a filter for complete weather resistance when desired.

Fluorine coating

Helps keep lenses clean by reducing the possibility of dust and dirt adhering to the lens and by facilitating cleaning should the need arise. Applied to the outer surface of the front and/or rear lens elements over multi-coatings.


Lens filters are accessories that can protect lenses from dirt and damage, enhance colors, minimize glare and reflections, and add creative effects to images.

Lens hood

A lens hood or lens shade is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare. Flare occurs when stray light strikes the front element of a lens and then bounces around within the lens. This stray light often comes from very bright light sources, such as the sun, bright studio lights, or a bright white background.

The geometry of the lens hood can vary from a plain cylindrical or conical section to a more complex shape, sometimes called a petal, tulip, or flower hood. This allows the lens hood to block stray light with the higher portions of the lens hood, while allowing more light into the corners of the image through the lowered portions of the hood.

Lens hoods are more prominent in long focus lenses because they have a smaller viewing angle than that of wide-angle lenses. For wide angle lenses, the length of the hood cannot be as long as those for telephoto lenses, as a longer hood would enter the wider field of view of the lens.

Lens hoods are often designed to fit onto the matching lens facing either forward, for normal use, or backwards, so that the hood may be stored with the lens without occupying much additional space. In addition, lens hoods can offer some degree of physical protection for the lens due to the hood extending farther than the lens itself.


Teleconverters increase the effective focal length of lenses. They also usually maintain the closest focusing distance of lenses, thus increasing the magnification significantly. A lens combined with a teleconverter is normally smaller, lighter and cheaper than a "direct" telephoto lens of the same focal length and speed.

Teleconverters are a convenient way of enhancing telephoto capability, but it comes at a cost − reduced maximum aperture. Also, since teleconverters magnify every detail in the image, they logically also magnify residual aberrations of the lens.

Lens caps

Scratched lens surfaces can spoil the definition and contrast of even the finest lenses. Lens covers are the best and most inexpensive protection available against dust, moisture and abrasion. Safeguard lens elements - both front and rear - whenever the lens is not in use.