PENTAX ME-F

The Pentax ME-F came out in 1981 as Pentax's first camera with automatic focusing. It kept the compact look of the ME series and paired manual focus lenses with an autofocus system that depended on a dedicated motorized lens. That was a big step for Pentax.

Overview

The Pentax ME-F was released in October 1981 by Asahi Optical Co. It was the successor to the popular Pentax ME and ME Super, and it was aimed at enthusiast photographers who wanted advanced automation in a compact, well-engineered 35mm SLR. It sat between the entry-level ME Super and the more professional LX in Pentax's lineup. It offered aperture-priority autoexposure plus autofocus - but only with a single, specially designed lens.

The ME-F used a hybrid approach to autofocus. The body held the AF sensor and processing circuitry, and the focusing motor sat inside the lens. That made it one of the first SLRs with a lens-integrated autofocus motor. The catch was that it required the proprietary SMC Pentax AF 35-70mm f/2.8 lens, the only autofocus lens ever produced for the system. It predated the fully integrated autofocus systems that would dominate the late 1980s.

The ME-F was a technological testbed rather than a commercial success. Its complex design, high cost and limited lens compatibility held back sales. It did lay the groundwork for Pentax's later autofocus efforts, including the Pentax SFX (SF1 in North America) of 1987, which had in-body autofocus drive and broader lens support.

Specifications

Specification	Value
Type	35mm Single-Lens Reflex (SLR)
Film Format	35mm (135 film), full-frame (24 x 36mm)
Years Produced	1981–1984
Lens Mount	Pentax K-mount (with electrical contacts for AF)
Shutter	Vertical-travel, focal-plane shutter; speeds from 4 sec to 1/1000 sec, plus Bulb (B), and flash sync at 1/60 sec
Metering	TTL open-aperture center-weighted averaging metering with silicon photodiode (SPD) sensor
Exposure Modes	Aperture-priority autoexposure, manual exposure (set via lens aperture ring), stop-down metering for off-brand lenses
Viewfinder	Fixed pentaprism with interchangeable focusing screens; standard screen includes microprism collar and split-image rangefinder; 92% coverage, 0.95x magnification (with 50mm f/1.4 at infinity)
Dimensions	135 × 81 × 50 mm (5.3 × 3.2 × 2.0 in); weight approximately 580 g (20.5 oz) body only (with battery)

Key Features

World’s First TTL Phase-Detection AF in an SLR (via lens motor): The ME-F featured an integrated autofocus system using a phase-detection sensor in the camera body, with focusing driven by a motor in the SMC Pentax AF 35–70mm f/2.8 lens—the first such implementation in a production SLR.
Aperture-Priority Automation with Manual Override: Allowed photographers to set the aperture on the lens while the camera automatically selected the correct shutter speed; manual exposure possible via stop-down metering.
Dedicated AF Lens with Integrated Motor: The SMC Pentax AF 35–70mm f/2.8 included a built-in DC motor, battery compartment, and AF/MF switch, making it the only lens capable of autofocus on the ME-F.
Compact, Lightweight Chassis: Built on the proven ME Super platform, the ME-F retained a compact metal-and-polycarbonate body ideal for travel and street photography.
LED Exposure Display in Viewfinder: Used a three-segment LED (under, correct, over) to indicate exposure status, a hallmark of Pentax’s electronic SLRs of the era.

Historical Context

The early 1980s were a busy time for SLR technology, with makers racing to get practical autofocus working. Konica's C35 AF (1977) and Polaroid's SX-70 Sonar (1978) had already shown autofocus in rangefinder and instant cameras, but SLRs lagged because of their mechanical complexity. The Pentax ME-F arrived just months before Nikon's manual-focus FM2 and before Minolta's Maxxum 7000 (1985), which brought in-body AF drive and integrated lens motors.

The ME-F ran into trouble right away. The sole AF lens was expensive and heavy, and it focused slowly and noisily, which reflected the limits of early motor and battery technology. Canon and Nikon were still refining manual-focus systems, while Minolta was secretly developing a fully electronic mount. The ME-F had no ecosystem around it. Market reception was lukewarm; enthusiasts appreciated the engineering, but most consumers found it impractical. Production ceased by 1984, with .

Collectibility & Value

Today the Pentax ME-F is a sought-after collector's item, valued as Pentax's first autofocus camera and for its rarity. Complete sets with the SMC Pentax AF 35-70mm f/2.8 lens typically sell for $400 to $800 depending on condition, and fully functional autofocus systems are the most prized. Production was limited and the lens's motor and circuitry are fragile, so a working ME-F is increasingly hard to find.

Check the lens's battery compartment first, since it is prone to corrosion from old PX27 batteries. Test the autofocus mechanism, which often seizes or loses calibration, and verify the camera's silver oxide battery (SR44 or equivalent). The ME-F uses a single 6V 4LR44 battery for camera functions and a separate 6V PX27 for the lens motor. Both are now obsolete and need adapters or modern equivalents. Common issues include degraded rubber seals, shutter timing inaccuracies and worn mirror dampers.

Similar Cameras

Minolta Maxxum 7000 (1985) – The first fully integrated autofocus SLR with in-body motor drive and electronic mount.
Nikon F3AF (1983) – A variant of the F3 with autofocus capability using two specialized lenses containing focus motors.
Canon A-1 (1978) – Featured advanced automation including shutter-priority and program modes, though manual focus only.
Olympus OM-2N (1980) – Competitor in the compact SLR segment with aperture-priority and TTL flash.
Yashica FX-3 (1982) – Budget-friendly aperture-priority SLR with similar size and targeting similar users.

Repair & Maintenance

The Pentax ME-F uses a 6V 4SR44 battery (or equivalent) for camera functions. The 4LR44 is alkaline and not recommended because of voltage drop and leakage risk; the original specification calls for 4SR44 (silver oxide). The SMC Pentax AF 35-70mm f/2.8 lens needs a separate 6V PX27 battery to power the focusing motor. That battery is now obsolete, though modern equivalents like the Wein Cell (zinc-air) or 4SR44 can be used with caution. Battery leakage is common, particularly in the lens compartment, and leads to corrosion on contacts and circuit boards.

The autofocus system is prone to failure from motor wear, dried lubricants or degraded wiring in the lens's flexible ribbon cables. Shutter reliability is generally good but may need CLA (clean, lubricate, adjust) service after decades of dormancy. The camera's electronics are relatively simple by modern standards, but replacement parts are scarce. Repair is feasible for experienced technicians familiar with vintage Pentax systems. Full restoration, especially of the AF lens, can be costly and time-intensive. Regular use, proper storage and removing the batteries when the camera is not in use are essential for long-term preservation.