PETRI FLEX 7

Name: Petri Flex 7
Brand: Petri

The Petri Flex 7 is a 35mm single-lens reflex (SLR) camera introduced in 1964 by Kuribayashi Shashin Kōgyō (later known as Petri Camera Co., Ltd.). Its 1/2000-second shutter speed stands out in Petri's SLR lineup. That was rare among Japanese SLRs of the mid-1960s. Petri aimed it at serious amateur and semi-professional photographers.

Overview

The Flex 7 came out while Japanese SLR design was changing fast, and makers were trying to compete with the growing dominance of Nikon, Canon, and Pentax. Petri was known for compact 35mm rangefinders and subminiature cameras. It entered the SLR market with a series of Flex models beginning in the late 1950s. The Flex 7, launched in 1964, was the top of that line, with advanced engineering and high-speed capability for performance-minded users.

Petri targeted advanced amateurs and photojournalists. The Flex 7 had a vertically traveling focal-plane shutter capable of 1/2000 sec - the fastest shutter speed on any Japanese 35mm SLR at its launch, matching the optional high-speed unit for the contemporaneous Nikon F. It used a fixed pentaprism with a ground-glass focusing screen. Through-the-lens (TTL) viewing came with a split-image rangefinder spot in the center for more accurate manual focusing. Lenses mounted on Petri's proprietary 48mm screw mount (often called the "Petri 48mm thread mount"), which supported automatic diaphragm functionality.

The Flex 7 stayed fully mechanical, with no built-in light meter. That put it in the same category as early Pentax Spotmatic prototypes and the Nikon F without metered prisms. The lack of metering reflected cost constraints and the camera's design philosophy: a rugged, high-performance tool for users who relied on external meters or experience. Production ran until 1969, when Petri shifted toward simpler, more cost-effective models as competition grew from Japanese SLRs with integrated metering and faster lens systems.

Specifications

Specification	Value
Type	35mm Single-Lens Reflex (SLR)
Film Format	35mm (135 cartridge)
Years Produced	1964–1969
Lens Mount	Petri 48mm screw mount (with automatic diaphragm linkage)
Shutter	Focal-plane, cloth-curtain; speeds 1 sec – 1/2000 sec + B; X-sync at 1/60 sec
Metering	None (unmetered)
Exposure Modes	Manual only
Viewfinder	Fixed pentaprism with ground-glass screen and central split-image rangefinder
Dimensions	Approx. 145 × 95 × 55 mm; Weight: ~680 g (body only, no lens)

Key Features

1/2000 sec shutter speed: One of the first Japanese SLRs to offer this high-speed capability, enabling sharp action photography in bright light.
Petri 48mm screw mount: Supported a range of Petri and third-party lenses with automatic diaphragm coupling.
Mechanical reliability: Fully mechanical operation with no batteries required, suitable for use in extreme conditions.
X-sync at 1/60 sec: Flash synchronization compatible with electronic flashes and bulbs.
Interchangeable focusing screens: Optional screens available for different shooting applications (e.g., microprism, grid).

Historical Context

The Petri Flex 7 was introduced at a critical juncture in the evolution of the 35mm SLR. By 1964, the SLR had begun to supplant rangefinders as the preferred format for serious photographers, driven by the success of the Asahi Pentax and Nikon F. Petri, aiming to establish credibility in this competitive segment, leveraged its experience in precision mechanics to deliver a technically impressive model. The 1/2000 sec shutter was a headline feature, achieved through a vertically traveling dual-curtain mechanism—a design that reduced shutter lag and allowed higher speeds than the more common horizontal shutters of the era.

Competitors at the time included the Nikkorex F (1962), Canonflex R (1960), and early Minolta SR-T models. Most of these topped out at 1/1000 sec. The Flex 7's speed advantage was short-lived, as electronic shutters and improved mechanical designs soon made 1/2000 sec more common. Market reception was limited by the lack of built-in metering and a relatively small lens ecosystem compared to Pentax's M42 or Nikon's F-mount systems. The Flex 7 stayed a niche product, appreciated by technicians and speed enthusiasts but overshadowed by more versatile offerings.

Collectibility & Value

Today the Petri Flex 7 is sought after by vintage camera collectors, particularly those interested in mechanical engineering milestones and rare high-speed SLRs. It combines a 1/2000 sec shutter with all-mechanical operation. Units in working condition typically sell for $150 - $300 USD, depending on lens inclusion, cosmetic state, and shutter functionality.

When purchasing a Flex 7, collectors should verify shutter operation across all speeds, especially at the extremes (1 sec and 1/2000 sec), as cloth shutters from this era are prone to stick or tear. The automatic diaphragm linkage should also be tested with a compatible lens. Common issues include light seals degradation, prism haze, and lubricant hardening in the film advance mechanism. Original Petri lenses—such as the Color Petri 55mm f/1.8 or 135mm f/3.5—are rare and add significant value. Complete sets with original case and manuals command premium prices.

Similar Cameras

Nikon F (1959) with High Speed Motor Drive (1/2000 sec option)
Pentax Spotmatic (1964) – M42 mount, TTL metering
Canon FX (1964) – Canon’s first unmetered SLR
Yashica Pentamatic (1959) – Early Japanese SLR with pentaprism
Fujica ST 705 (1968) – Later model with 1/2000 sec and metering

Repair & Maintenance

The Petri Flex 7 needs no batteries and operates entirely mechanically. That makes it reliable in long-term storage, but the precision shutter and film transport mechanisms need careful maintenance. The cloth focal-plane shutter is susceptible to wear, particularly at high speeds, and a technician experienced with vintage Japanese SLRs should service it. Common issues include slow shutter speeds from dried lubricants and inconsistent curtain travel. The film advance lever can bind if the internal gears are gummed with old oil. Light seals should be replaced to prevent light leaks and fogging. Parts are rare, so repairability is moderate - many components are serviceable, but replacement shutters or viewfinders are not readily available. Regular use and cleaning are recommended to keep the camera functional.