Petri GX-3

The Petri GX-3 is a SLR camera. It was introduced by Petri in the 1980s. It is the successor to the Petri GX-2. It was produced in a Cosina factory in Japan. Cosina also offered it as the Cosina CT-20.

The biggest differences from the Petri GX-2 are the built-in self-timer and exposure compensation for backlit shots.

Lens Mount and Focusing

A key feature of the Petri GX-3 is its interchangeable lens mount, which gives the user the flexibility to optimally adapt the lens to the respective shooting situation and the desired image quality.

The camera is equipped with the widely used Pentax K bayonet, making it compatible with a wide range of lenses from different manufacturers and with different focal lengths – from wide-angle to normal to telephoto lenses. This opened up extensive creative possibilities for the photographer.

This classic 35mm camera does not have an autofocus function. Instead, focusing on the subject is done entirely manually by turning the focusing ring on the lens, which requires deliberate and precise composition and is often supported by adjustment aids such as a split-image indicator and a microprism ring in the viewfinder.

Exposure Metering and Control

For precise determination of the correct exposure settings, the Petri GX-3 features a reliable light meter. This is designed for use with 35mm film with a sensitivity range of ISO 25 to ISO 1600.

Exposure metering on this SLR camera is typically done “Through The Lens” (TTL), i.e., directly through the attached lens. This ensures high accuracy, as the light actually falling on the subject is captured.

The camera operates in aperture priority mode: the photographer can freely select the desired aperture on the lens, for example, to creatively influence the depth of field. The camera’s electronics then automatically determine the correct shutter speed and set it independently. The selected shutter speed is usually indicated to the photographer via an LED display in the viewfinder.

Shutter functions, flash, and other features

The 35mm camera features a bulb mode (B setting), which is essential for shots with very long exposure times, such as those required in night or astrophotography. In this setting, the shutter remains open as long as the shutter button is held down.

To expand the lighting options, especially in unfavorable lighting conditions or for creative lighting, an external flash unit can be connected and triggered via the standardized hot shoe connector on the top of the camera.

For maximum stability and blur-free shots, especially with longer exposure times, the Petri GX-3 is equipped with a thread on the bottom of the housing for attaching it to a tripod.

The camera also offers a connection for a mechanical cable release to minimize camera shake when pressing the shutter button. Another important feature that sets it apart from simpler models is the integrated self-timer, which allows the photographer to become part of the subject with a delay of typically a few seconds or to completely avoid camera shake by pressing the shutter button.

Dimensions, Weight, and Power Supply

According to the available specifications, the Petri GX-3 weighs approximately 450 grams without lens and batteries and measures 13.3 cm wide, 8.5 cm high, and 4.8 cm deep. These measurements make it a comparatively compact and lightweight SLR camera for its time. Power for the light meter and the camera’s electronic functions is provided by two S76 button cells (often equivalent to LR44 or SR44 batteries), which are inserted into a compartment on the bottom of the camera.

Films for the Petri GX-3

The Petri GX-3 uses standard 35mm film, as stated in the instruction manual and specifications. This film format is still readily available today and is developed by numerous labs worldwide.

Recommendations for this camera include the Fujifilm Superia 400* for colorful, everyday shots with good flexibility. For black-and-white enthusiasts, the Ilford XP2 Super* is a good choice, as it has the advantage of being able to be developed using the standardized C-41 color negative process, making it easier to find a lab.

It is common practice and the industry standard to process color negative films using the C-41 development process. The C-41 process is internationally standardized and is offered by the vast majority of professional photo labs, ensuring trouble-free film development.

The 35mm camera exposes an area of ​​24 mm x 36 mm on the film. After each shot, the film in the camera must be manually wound to the next frame, as there is no automatic film advance mechanism. This is usually done via a quick-release lever.

Production of the Petri GX-3 was discontinued many years ago. Today, it is available exclusively on the used market, where it is prized by collectors and enthusiasts of analog photography. The value of a used camera is largely determined by its condition, functionality, and any accessories it may have.