Cosina CT-10

The Cosina CT-10 is a 35mm analog single-lens reflex (SLR) camera. It was sold in the 1980s. It was manufactured by the Cosina company in Japan. A functionally identical model was sold under the name Petri GX-2. There was also the Cosina CT-20, which came with an additional self-timer and backlight correction.

Lens

The Cosina CT-10 features a Pentax K bayonet mount, a widely used lens mount that allows compatibility with a wide variety of lenses from different manufacturers.

The specific flange focal length (flange focal length) is 45.44 mm.

The camera was often shipped with a standard lens, typically a 50mm prime lens such as the Cosina-S 50mm 1:1.8 pictured. Thanks to the K-mount, however, users can use lenses with different focal lengths and apertures, from wide-angle to telephoto lenses.

Focusing is done manually using the focusing ring on the lens. A centrally located split-image indicator surrounded by a microprism ring serves as a focus aid in the viewfinder. The image is in focus when the two halves of the split image are precisely aligned and the image in the microprism ring appears clear and no longer flickering.

A depth of field scale is usually present on the lenses, as is a distance scale. An infrared marker, usually a red line or dot, helps with focus adjustment for infrared photography.

The aperture and filter thread are properties of the lens used, not of the camera itself.

Changing lenses is done by pressing the lens release button on the camera body and turning the lens counterclockwise.

Exposure Settings

The Cosina CT-10’s exposure system is based on TTL (Through The Lens) metering with a silicon photodiode (SPC). The metering is center-weighted, meaning the central area of ​​the image field is given greater weight to ensure balanced exposure for most subjects.

The camera operates in aperture priority mode. The photographer selects the desired aperture using the lens’s aperture ring, and the camera’s electronics automatically determine and set the appropriate shutter speed.

The exposure metering range is from EV 2 to EV 19, measured at ASA 100 with a lens with a maximum aperture of f/1.4 to f/22.

The film speed is set manually using the film speed dial and ranges from ASA 25 to ASA 1600.

The shutter is a magnetically controlled, vertically moving metal-blade focal plane shutter with shutter speeds from 4 seconds to 1/1000 of a second, as well as a “B” (bulb) setting for long exposures, where the shutter remains open as long as the shutter button is pressed.

In the viewfinder, light-emitting diodes (LEDs) on the left side indicate the automatically selected shutter speed and the exposure situation.

A green LED indicates a range suitable for handheld shooting, typically from about 1/30 of a second to 1/1000 of a second.

A yellow LED warns of slower shutter speeds below 1/30 of a second, where the use of a tripod or flash is recommended to avoid camera shake.

A red LED indicates overexposure; In this case, a smaller aperture, i.e., a higher aperture value, should be selected.

Exposure compensation can be made manually by adjusting the ASA setting, for example, by setting it to ASA 25 when using ASA 100 film to achieve overexposure by two f-stops.

Flash System

The Cosina CT-10 is equipped with a standard hot shoe with a center contact. The flash sync speed is 1/100 second.

When using third-party flash units or manual flash units, the camera’s mode dial must be set to the “X” position, which sets the shutter speed to 1/100 second.

The camera has been optimized for use with the dedicated Cosina Speedlight Auto-160 and Auto-220 flash units. When one of these flash units is attached and turned on, and the camera’s mode switch is set to “AUTO,” the shutter speed is automatically synchronized to 1/100th of a second as soon as the flash unit signals that it’s ready to charge. This readiness is also indicated by a red “F” LED in the viewfinder.

The correct aperture for flash exposure must be set on the lens according to the instructions for the flash unit in use.

Additional Features

In addition to its core functions, the Cosina CT-10 offers several additional features. It has a connection for a mechanical cable release in the shutter release button, a standard 1/4-inch tripod thread on the bottom, and eyelets for attaching a camera strap.

A frame counter on the top shows the number of images taken and automatically resets to “S” (Start) when the back is opened. A film memo holder on the back serves as a reminder of the film type loaded.

Dimensions and Weight

The camera body of the Cosina CT-10 measures 133 mm (width) x 85 mm (height) x 48 mm (depth). The body alone, without lens and batteries, weighs 450 grams. These dimensions and weight make it a comparatively compact and lightweight SLR camera for its time.

Power Supply

The exposure metering system and viewfinder LEDs are powered by two 1.5-volt button cells. Compatible battery types are S-76 (eBay / Amazon*), A-76, G-13, or equivalent alkaline manganese (LR44) (eBay / Amazon*) or silver oxide (SR44) cells (eBay / Amazon*).

The batteries are inserted into a compartment on the bottom of the camera, which can be opened with a coin. The correct polarity is indicated on the inside of the battery compartment cover.

A battery check is integrated: When the mode switch is set to “AUTO” and the shutter button is lightly pressed, one of the LEDs in the viewfinder should light up, provided the batteries provide sufficient voltage. If no LED lights up, the batteries must be replaced.

It is recommended to remove the batteries approximately once a year or when the camera is not in use for an extended period to prevent leakage.

Film Recommendations for the Cosina CT-10

The Cosina CT-10 uses standard 35mm film (eBay / Amazon*). The camera supports films with sensitivities from ASA 25 to ASA 1600, which corresponds to ISO 25 to 1600.

There is no DX coding for automatic detection of film sensitivity; the ASA/ISO value must be set manually using the selection dial. The choice of film depends on the subject and lighting conditions.

Low-sensitivity films, such as ISO 25 to 100, are ideal for shooting in bright daylight, landscape photography, or when the highest level of detail and the finest grain are desired. They require longer exposure times or larger apertures in low light.

Medium-sensitivity films, such as ISO 200 to 400, are versatile for general photography in a variety of lighting conditions, portraits, travel, and snapshots, offering a good compromise between fine grain and light sensitivity.

For low-light photography, such as indoors or at dusk, for sports photography, to enable fast shutter speeds, or when a greater depth of field is needed in low light, high-sensitivity films from ISO 800 to 1600 are suitable, although grain becomes more visible here.

Quick Operation Guide

1. Inserting Batteries: Open the battery compartment on the bottom with a coin and insert two matching 1.5V batteries (e.g., LR44/SR44) with the correct polarity. Close the compartment.
2. Checking Batteries: Set the mode switch to “AUTO,” press the shutter button halfway, and check if an LED in the viewfinder lights up.
3. Loading Film: Pull the rewind knob up to open the back cover. Insert the film cartridge into the film chamber, pull the film tab up to the take-up spool, and thread it into the slot or under the spool clamp. Make sure the perforation engages the teeth of the advance wheel.
4. Film advance: Operate the film advance lever and the shutter release button several times until both rows of perforations engage securely. Close the back.
5. Advance film: Operate the film advance lever and the shutter release button until the frame counter reaches “1.” When cocking, the rewind knob should turn counterclockwise – a sign that the film is being advanced correctly.
6. Set the film speed: Set the ASA/ISO value of the loaded film using the film speed dial.
7. Select the shooting mode: Set the mode dial to “AUTO” for shutter priority, “X” for flash photography (1/100s), or “B” for long exposures.
8. Select the aperture: Set the desired aperture using the lens aperture ring.
9. Focus: Look through the viewfinder and turn the lens focus ring until the subject appears sharp in the split image/microprism field.
10. Check the exposure: Press the shutter button halfway and watch the LED indicator in the viewfinder. Adjust the aperture if necessary.
11. Release: Press the shutter button all the way down to take the photo.
12. Rewind the film: After the last shot, press the film rewind button on the bottom of the camera. Unfold the crank on the rewind button and turn it clockwise until you feel less resistance. Open the back and remove the film cartridge.