Petri PX7

The Petri PX7 is a compact 35mm viewfinder camera, designed for straightforward operation. It was produced in the 1980s by the Japanese company Cosina. Cosina offered a similar model under the name “Cosina CX7”.

Lens and Focusing

At the heart of the PX7 is a fixed lens, meaning you cannot swap it for other focal lengths. The lens is clearly labeled “Petri f/3.5 33mm”. This indicates a focal length of 33mm, which provides a moderately wide-angle perspective – slightly wider than the classic 50mm “standard” lens, making it versatile for general snapshots, landscapes, and group photos.

The maximum aperture is f/3.5, which is reasonably bright for daylight conditions or use with flash, though less suited for very low light shooting without flash assistance.

Focusing is handled automatically. The autofocus system takes the guesswork out of achieving sharp images, allowing the user to simply point the camera at the subject and shoot.

However, the lens has limitations in close-up capability; its closest focusing distance is 1.2 meters (120 cm). This means it’s not designed for macro photography of very small objects but is adequate for subjects like portraits or objects at a moderate distance.

Exposure and Film Sensitivity

The camera incorporates a built-in exposure meter to measure the ambient light. It’s designed to work correctly with films within an ISO sensitivity range of 64 to 400. This range covers common film speeds suitable for sunny days (ISO 100/200) up to slightly more overcast conditions or faster action (ISO 400).

The Petri PX7 features an automatic exposure mode. This system intelligently adjusts both the aperture and shutter speed based on the light meter’s reading, ensuring a balanced exposure without requiring manual input from the photographer. This automation makes it exceptionally user-friendly, especially for beginners.

Built-in Flash

For situations where ambient light is insufficient, such as indoors or during twilight, the PX7 includes a built-in electronic flash. This provides necessary illumination to capture photos in low-light scenarios.

The manufacturer specifies the effective flash range as 1,2 to 6 meters (likely based on ISO 100 film). Subjects closer than 1,2m may appear overexposed, while those beyond 6 m might be too dark when relying solely on the flash.

As with most compact cameras, the close proximity of the flash to the lens might increase the chance of red-eye in portraits.

Physical Characteristics and Power

In terms of handling, the Petri PX7 is relatively portable. It has a weight of approximately 280 grams and dimensions of 11.7 x 7.2 x 4.3 cm, making it easy to slip into a bag or carry around for extended periods.

Its construction is likely typical of consumer cameras from its time, featuring a predominantly plastic body. Powering the camera’s electronics, including the autofocus, light meter, and flash, requires two standard AAA batteries (eBay / Amazon*), which are inexpensive and widely available.

Films and Image Format for the Petri PX7

To capture photographs, the Petri PX7 requires standard 35mm film (135 format). Fortunately, despite the rise of digital photography, 35mm film is still readily available from various manufacturers and processing services remain common.

You can load the PX7 with either color or black and white film. For example:

• Color: Fujifilm Superia 400* is a popular choice, offering good versatility with its ISO 400 rating.
• Black and White: Ilford HP5* is a classic high-speed black and white film, also rated at ISO 400.

Color negative films like the Fujifilm example are developed using the ubiquitous C-41 process. Nearly all photo labs offering 35mm film development utilize this standard process. Black and white films, like the Ilford HP5, require specific black and white chemical processing, which is offered by specialist labs or can be undertaken by enthusiasts at home.

Each picture taken with the Petri PX7 produces a negative measuring 24mm x 36mm, the standard “full-frame” size for 35mm photography. On a typical roll labeled “36 exposures” (e.g., 135-36), you can expect to capture approximately 36 photos.

The film transport mechanism in the camera requires manual winding; after taking each shot, the user must typically advance the film to the next frame using a thumbwheel. Similarly, rewinding the film back into the canister at the end of the roll is usually a manual process.

Availability and Value

The Petri PX7 is no longer manufactured. As a vintage camera, it can be found on the second-hand market, appearing on online auction sites, classifieds, or occasionally in thrift stores or camera fairs. The price for a used copy varies considerably depending on its cosmetic condition, operational status (ensure the autofocus, flash, and meter are working), and whether it comes with any original packaging or accessories. It represents an affordable entry point into the world of analog point-and-shoot photography.