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A true system camera allows users to continue to use their system units when new camera model appears. To maintain full interchangeability among all OM System units, the exterior design of the OM-3 and OM-4 is fundamentally the same as the OM-1 and OM-2.

Fitting a host of new features - the powerful microcomputer required for Multi Spot Metering, the LCD viewfinder display mechanism, the dioptric adjustment mechanism, showerproofing material, etc - into the tiny camera body is a challenging task.

Another problem is where to position the new spot metering controls: the Multi Spot Button, Highlight Button, Shadow Button, Memory lever and Clear Lever. This is one of the toughest challenges of the whole design project, because the essence of the Multi Spot Metering concept is predicated on quick, simple operation.

These controls are grouped around the shutter release. They differ in shape, size, position and height for easy recognition and effortless operation. The pentaprism section is redesigned to fit with the overall more modern, attractive appearance.

The reason the OM-3(4) is just a fraction larger than the OM-1(2) has nothing to do with the Multi Spot Metering function, or with the many other refinements incorporated. The extra millimeter is taken up by a layer of shower resistant sealings.

This rubber or foam-plastic gaskets make the camera considerably more resistant to inclement weather and impact.

Shower resistant sealings

Part of the OM-3Ti and OM-4Ti body is constructed of tough and lightweight titanium.

The exceptional strength of titanium makes it extremely difficult to process. A deep pressing process is employed, which is one of the most difficult of press technologies.

Olympus engineers spend several years of research in perfecting the press process. The result is a super tough titanium shell with the same accuracy and smoothness as the brass shell used in the original OM-3 and OM-4.



OM4 shutter mechanism


In OM-4, a completely redesigned block-type shutter is used. The new shutter mechanism features some 50 improvements over the original design. It is designed to assure easy assembly and more uniform quality, running, drive and control functions.

It has a low-shock full horizontal focal plane shutter which provides an accurate and constant 1/2000 sec shutter speed. The increased spring tension on the shutter curtains could result in a greater tendency for the curtains to bounce back at the end of their travel. An improved curtain-brake system is employed to prevent this.

Two electromagnets are used to control the exposure times; one is used to trip the camera, another to arrest the closing curtain.

In the mechanical 1/60sec and B settings, a cam shifts the camera-tripping duties from the electromagnet to mechanical pressure from the user's finger. The difference in the shutter button's action in either mode is very small.

A mechanical shutter mechanism is used in OM-3. One of the difficulties in developing the OM-3 is to achieve an accurate 1/2000sec shutter speed, especially in low temperature.


OM3 shutter mechanism



OM3 winding mechanism



OM3Ti shutter mechanism




The finder display is the secret that makes Multi Spot Metering manageable. A negative type large-size LCD is used.

The LCD display is located in front of the pentaprism. Light coming from the scene passes through a diffusing strip above the camera's front nameplate. It is then directed through the LCD panel by a molded plastic prism. The light path runs along the front of the prism to its base, passing through a condenser lens and parallel prisms to reach the viewfinder.

Under dark conditions, a miniature incandescent lamp is used to illuminate the LCD.

The viewfinder features a continuous dioptric adjustment from -3 to +1.

A flat cover glass on the outside protects the two-element ocular inside. The two elements both move during the ocular focusing action. The positive lens moves more than the negative one. It is all done within just a bit more space than a conventional, nonfocusing ocular. Roller bearings assure smooth, continuous dioptric adjustment.


Parts of the flexible circuit are coated with a vapor-barrier substance to prevent shorting out in high humidity. Switches and other electrical contact points are gold-plated or treated against oxidation.











OM-3 Test Report
OM-4 Test Report
OM-3, OM-4 Catalog

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Last updated on 28 January, 2004
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