PENTAX MX

Name: Pentax MX
Brand: Pentax

The Pentax MX is a compact, fully mechanical 35mm film SLR introduced in 1976 as a professional-grade manual focus camera. It was small, light and built to last. Photojournalists and enthusiasts who wanted something lighter than the big professional SLRs took to it.

Overview

Asahi Optical Co. (later Pentax) introduced the MX in 1976 as a compact, high-precision mechanical SLR for professionals and advanced amateurs. Electronic automation was becoming common by then, but many professionals still wanted fully mechanical operation for reliability in extreme conditions. The MX sat between the larger Pentax LX (released in 1980) and the consumer-oriented Pentax K1000. The shutter is mechanically controlled and needs no battery for basic operation - the built-in light meter is the only thing that does.

The MX was small and light, especially next to contemporaries like the Nikon F2 or Canon F-1. It still carried a full set of professional features: a high-quality pentaprism viewfinder with interchangeable focusing screens, a vertical-travel cloth focal-plane shutter, and a brass chassis inside a magnesium alloy body shell. It took the full range of Pentax K-mount lenses (with mechanical aperture coupling), so a wide array of optics fit.

The MX stayed in production until 1985, longer than many expected, thanks to its loyal user base and mechanical reliability. It is often regarded as one of the last compact mechanical professional SLRs before the industry moved decisively to electronic automation and autofocus.

Specifications

Specification	Value
Type	35mm Mechanical SLR
Film Format	35mm (135)
Years Produced	1976–1985
Lens Mount	Pentax K-mount (mechanical aperture coupling)
Shutter	Vertical-travel cloth focal-plane; speeds from 1 sec to 1/1000 sec, plus B (Bulb)
Metering	TTL open-aperture CdS metering (center-weighted)
Exposure Modes	Manual only
Viewfinder	Interchangeable focusing screens; fixed pentaprism with 0.92× magnification, 100% coverage
Dimensions	136 × 82 × 47 mm (5.35 × 3.23 × 1.85 in); ~590 g (body only, without battery)

Key Features

Fully mechanical operation: Shutter functions without batteries; only the light meter requires power (1× 1.35V mercury battery, originally PX625, later replaced by Wein Cell or adapters for modern 1.5V alternatives).
Compact and lightweight professional build: At just under 600 g, it was one of the smallest professional SLRs of its era, ideal for travel and photojournalism.
Precision vertical-travel shutter: Offers reliable speeds from 1 sec to 1/1000 sec with excellent flash synchronization at 1/60 sec.
Interchangeable focusing screens: Allows customization for different shooting needs (e.g., split-image, microprism, grid).
100% viewfinder coverage with 0.92× magnification: Unusual for its size, providing accurate composition and critical focusing.

Historical Context

The MX arrived while Japanese SLR makers were rapidly adding electronics to their cameras. Nikon (F2, 1971; later F3 in 1980) and Canon (F-1, 1971; New F-1 in 1981) were building large, modular professional bodies. Pentax went the other way with the MX, stressing compactness and mechanical simplicity without giving up build quality or optical performance.

The MX was developed in part to answer demand for a smaller, more portable alternative to the bulky flagship models. The earlier Pentax ME and MV influenced its design, but the MX was mechanically superior, with no electronic dependency for shutter operation. It was also released before the Pentax LX, which became Pentax’s true flagship. The MX took a position as a "mini-professional" camera, popular with photojournalists, street photographers, and travelers.

Despite having no automation, the MX received strong critical acclaim for its precision engineering and reliability. Notable photographers used it in the 1970s and 1980s, particularly where durability and manual control were paramount. It ran for nine years, even as electronic cameras gained dominance.

Collectibility & Value

Today the Pentax MX is a sought-after collectible among film photography enthusiasts, particularly those who like mechanical cameras and minimalist design. Used prices typically run from $150 to $350 USD, depending on condition, shutter functionality, and viewfinder clarity. Fully functional units with clean viewfinders and accurate metering (when adapted to modern batteries) command higher prices.

When buying an MX, check shutter accuracy at slow speeds, mirror movement smoothness, and the viewfinder prism for fungus or haze. The original CdS meter used a 1.35V mercury battery (PX625), which is no longer manufactured. Most users now run zinc-air replacements (e.g., Wein Cell) or voltage adapters, because 1.5V alkaline batteries can cause overexposure due to higher voltage.

The MX is relatively rare compared to mass-market models like the K1000, but not exceptionally scarce. Its reputation for quality keeps demand steady. Original boxes, manuals, and accessories (such as the DE-2 viewfinder magnifier or interchangeable screens) increase collectible value.

Similar Cameras

Nikon FM (1977) – Compact mechanical SLR with similar professional aspirations, aluminum chassis, and excellent build quality.
Canon FTb (1971) – Rugged mechanical SLR with full manual control and TTL metering; heavier but widely used.
Olympus OM-1 (1972) – Even smaller than the MX, the OM-1 pioneered compact SLR design with a high-quality viewfinder.
Minolta SRT-101 (1966–1972) – Known for robust build and advanced metering for its time; slightly older but comparable in use.
Pentax LX (1980) – Pentax’s flagship professional SLR, larger and more modular, but sharing engineering philosophy.

Repair & Maintenance

The Pentax MX uses a single 1.35V mercury battery (PX625) for its TTL CdS light meter. Mercury batteries are obsolete, so users commonly substitute Wein Cell zinc-air batteries (1.35V) or use adapters with 1.5V alkaline batteries (e.g., PX625A). The alkaline route may need exposure compensation of -⅓ to -½ stop to account for the higher voltage.

The mechanical shutter is highly reliable, but after decades of use it may need CLA (Clean, Lubricate, Adjust) service, especially if stored improperly. Common problems are sticky shutter curtains at slow speeds (1-1/30 sec) and degraded light seals, which should be replaced to prevent light leaks. The mirror damping system can also degrade, leading to loud or uneven mirror movement.

Repair parts are still available through specialized camera technicians, though the MX is not as widely serviced as the Nikon FM or Canon AE-1. Its mechanical simplicity and modular design mean experienced technicians can often restore it to full functionality. Regular use and proper storage (cool, dry environment) help maintain long-term reliability.