Topcon Unirex

Introduction: The Unirex at a Glance

Among SLR film cameras, Topcon's Unirex counts as a genuine curiosity. Tokyo Kogaku produced it between 1969 and 1973 as a 35mm single-lens reflex that measures light through the lens, and its lenses attach with a bayonet. The example photographed here carries a UV Topcor 35mm f/3.5.

The interesting part is not visible from the front. The Unirex places a leaf shutter in the body, directly behind the lens mount, and that single choice shapes the whole design.

Working with a film SLR changes your pace. You choose a speed, judge the light, compose and press once, aware that each frame has a cost.

Design Roots and Historical Background

A leaf shutter where you would not expect one

A leaf shutter works like an iris: thin blades swing open from the centre and close again, instead of a curtain sweeping across the film. The Unirex achieves this with a Seikosha SVL unit inside the body, behind the lens position.

The practical result is that the lens carries no shutter at all. Every Topcor UV lens is therefore a complete, swappable unit.

Two versions and a successor

Buyers could choose between two variants. The standard Unirex meters either a small spot or the whole scene, whereas the Unirex EE dropped the spot option. A black finish was offered for each of them as well as the usual one.

Next in line came the Topcon IC-1 Auto. Sources give its launch as either 1973 or 1974, so the exact year is uncertain. It switched to a focal plane shutter. One rumour links that change to Seiko ending production of the SVL leaf shutter, although nothing confirms it.

Key Technical Highlights

Shutter and exposure

The body-mounted shutter offers times from one second to 1/500 second, together with a B setting and a self-timer. You can expose entirely by hand, or choose a time yourself and let the camera select the aperture. Between 1/15 and 1/500 second the automatic mode is available.

Sensitivity can be dialled in from ASA 25 up to ASA 1600.

Metering and viewfinder

Light is measured through the lens with the aperture wide open. A pair of CdS cells flank the viewfinder area, while a third sensor positioned behind the mirror handles spot readings, which isolate a small part of the scene.

For focusing, the screen is a Fresnel type with a microprism dot in the middle, ringed by a finer focusing zone. The finder magnification is 0.75x.

Mount, power and size

Lenses fit the UV Topcon bayonet, which can lock in place with Topcor UV optics. Power comes from a single 1.35V PX625 mercury cell, and a WeinCELL MRB625 zinc-air cell is named as a stand-in. The body measures 141 x 93 x 59 mm.

• Shutter: Seikosha SVL, 1 s to 1/500 s, plus B and self-timer
• Sensitivity: ASA 25 up to ASA 1600
• Viewfinder: Fresnel screen, microprism dot, 0.75x magnification
• Dimensions: 141 x 93 x 59 mm (width x height x depth)

Modern-Day Use in 2026

Where the Unirex excels

This camera appeals to photographers who want an SLR with its own character: a clear focusing aid, automatic or manual control, and a shutter arrangement few other reflexes share.

Use it for:

• Street and travel photography with a wide-angle view
• Slow, deliberate film practice with manual exposure
• Building a small collection of unusual SLR designs

Practical shooting tips

• Set the film speed to match the roll you loaded, and recheck it whenever you change film.
• Pick spot metering for a face against a bright background, and the averaging mode for ordinary scenes.
• Choose automatic mode when the light changes quickly, and go manual for times slower than 1/15 second.
• Brace the camera or use a tripod for slow speeds.

Buying and Maintenance Guide

What to check before buying used

Work through this checklist when you inspect a camera:

• Fire the shutter at every speed and listen for uneven or sticky sounds, especially at the slow settings.
• Look through the lens for haze, fungus, dust or scratches.
• Open the back and inspect the light seals and the film chamber for crumbling foam.
• Check the battery compartment for corrosion or green deposits.
• Compare the meter readings with a handheld meter or a phone app.

Power and batteries

The Unirex was designed around a 1.35V PX625 mercury cell. The WeinCELL MRB625 zinc-air cell is named as a replacement with matching voltage.

• Remove the battery when the camera will sit unused for a long time.
• Check the meter against a known source after fitting a new cell.

Basic care and accessories

A few photography accessories make ownership easier:

• A padded bag or case to protect the body and lens from knocks.
• Front and rear lens caps, kept on whenever you are not shooting.
• A microfibre cloth and a blower for dust on the lens.
• A small tripod for slow shutter speeds.

What to pay

On European marketplaces such as eBay, working examples are typically listed around €70–€155.

Conclusion: A Quiet Oddball

Topcon's Unirex is a 35mm SLR whose leaf shutter sits in the body, leaving every lens as one swappable piece. Add through-the-lens metering with a spot option and automatic or manual exposure, and you get a camera that is a pleasure to figure out.

It suits someone who enjoys mechanical details and does not mind inspecting an older camera with care.

Ready to explore cameras like the Unirex? Browse our selection of SLR film cameras and the wider range of analog cameras at DutchThrift.com.

Sources: original Topcon Unirex instruction manual (scans in English and German); Topcon Unirex on camera-wiki.org, text licensed under GFDL 1.3; price range based on eBay listings of complete working cameras.