The Exa Mirror/Shutter

Exa cameras were less-expensive versions of Exaktas that mostly took the same lenses and other accessories. (Exa is half of Exakta.)

I bought my Exa in a small antique store in Buffalo, Wyoming, in 2008. The dealer said he had used it in high school, and that it was a gift from his sister. I doubt if she bought it new, because from its serial number, 229249, it’s very old, dating from 1952 or 1953. If you’re interested in learning more about Exas and Exaktas, use Google to find several excellent and remarkably complete web sites.

Surely the strangest feature of the Exa is its shutter. It’s neither a focal-plane shutter nor a leaf shutter. Instead, it’s in the mirror box. The swinging mirror forms part of it, and another lower part forms the other part. McKeown’s Price Guide to Antique & Classic Cameras calls it a metal sector shutter.

I’ve read descriptions of this shutter on various Exa web sites, none of which are very clear about how it actually works. Some descriptions are wrong; others are just vague. So, I decided to take a look at mine and make some close-up photos. (For which I used a Nikon D700 with a Tamron 90mm macro. Lighting was from two SB-600 and SB-800 Speedlights angled to fire directly into the mirror box from the back and triggered wirelessly by the D700 in what Nikon calls commander mode. I like looking at and handling old cameras, not actually using them.)

When you wind the Exa to return the mirror so you can frame your next shot, the mirror moves very slowly, so I was able to get some shots of the mirror in-progress. I used the bulb setting (on the Exa, not the Nikon) to get shots of the shutter all the way open.

Once the shutter is wound, here’s how things start out:

The upper (mirror) and lower sectors are held together by a lip at the end of the upper sector for a light-tight seal. Here’s the photo, taken from the open back of the camera:

When the shutter opens, the mirror flips up, just as in most SLRs, but the lower sector stays down so the film can be exposed:

After the exposure (1/50 sec., say), the lower sector slides up to once again join the mirror (now raised) to seal off the light:

As you wind the film and reset the shutter, you can see the mirror moving back down, pushing the lower sector down as it goes. Notice how the two stay together to keep the film from being fogged.

The Exa combination mirror/shutter was a clever design that probably helped Ihagee keep costs down, but it had one horrible disadvantage: The fastest shutter speed was only 1/150 sec. The earliest Exas actually went to 1/250, but this was soon reduced, probably because of too many mechanical problems.