The Rolleiflex Automat is a professional twin lens reflex camera from 1949. It makes square 6x6cm negatives on 120 film. HOWEVER, if used with a "Rolleikin" kit, you can adapt the Rolleiflex Automat to use 35mm film. This is how I used the camera, mostly because I had just shot a roll with the very similar Minolta Autocord 6x6 TLR, and wanted a more unique experience.
The Rolleikin kit comes in a cute little box with all the parts you need to turn your camera into a 35mm shooting machine:
Yep, some assembly is required, but it's pretty intuitive. I only had to look up instructions once or twice. The most noticeable piece is the interchangeable back, which sports a 35mm frame counter. There's a little 35mm film-plane adapter that must be stuck into the film chamber, and various metal twiddly bits that must replace the 120 reels to allow 35mm film to advance and rewind properly. Once everything is installed, the mechanism works well.
The most obvious difference when shooting 35mm film with the Rolleiflex is field of view. With 120 film, the Rollei's 75mm lens provides a standard, even slightly-wide viewing angle. Since 35mm film is much smaller than 120, that 75mm lens gets cropped and turns into a short-telephoto, which totally switches up how the camera can be used. With the Rolleikin installed, the Rolleiflex is turned into a portrait machine. To help compose with the tighter field of view, the Rolleikin comes with a little mask you can slide on top of the focusing screen:
Since 35mm film is transported vertically with the Rolleikin, all photographs must be composed vertically. This was fine for me, since I pretty much only used the camera to make portraits (plus, vertical compositions > horizontal compositions). I found working under the restrictions of the Rolleikin to be a fun diversion. I mean, when's the last time you used a camera with a fixed telephoto lens? I enjoyed myself.
So enough about the Rolleikin, what about the Rolleiflex Automat itself?
Well, it's a fine twins lens reflex for its time. This K4/50 model is the second Rolleiflex to utilize the twin aperture and shutter speed dials set to the right and left of the lenses, which work beautifully. It's really easy to adjust and view aperture (f/3.5 ~ f/22) and shutter speed ( 1/500 ~ 1 sec). One small annoyance is how the 1/500th speed MUST be selected before the shutter is cocked. But hey, at least it's there. Most leaf shutters of the time maxed out at 1/300 or 1/400. The shutter release is lockable, and has a thread for cable releases.
The shutter is cocked and the film is advanced by turning a crank on the side of the camera. The film advance mechanism automatically stops on each frame. Double exposures and NOT possible, unfortunately. This camera comes from an age when multiple exposures were mostly only thought of as mistakes.
A major downside of this camera is its focusing screen. Ugh. It's extremely dim and dull, with no focusing assists (it has a plain matte screen with grid lines). Even under bright light, finding exact focus is extremely difficult and frustrating. With newer cameras, subjects POP into focus on the screen, but not so with this older model of Rolleiflex. While using the camera, I would continuously crank the focus back and forth, back and forth, and then ultimately just take an educated guess. A lot of shots turned out a bit soft, as a result.
Okay, so only after shooting a complete roll with this camera did I learn its strangest feature. On the back of the focusing hood is a magnifying glass, and if you flip down the hood's sportsfinder, there's a mirror on the underside of it. You can look through the magnifying glass, into the mirror, and actually view the focusing screen at eye-level. It's super cool, until you realize the eye-level view is inverted (upside-down), and heavily cropped. In the end, it's useless, but still a neat little party trick.
Below are some photos I made with the Rolleiflex Automat and Rolleikin adapter. I used TMax 400 35mm film.