Twin-lens reflex camera

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The front of a Kinaflex twin-lens reflex camera. The focus rings of the two lenses are coupled with gears around their circumference in this simple design.

Sketch of an early-20th-century twin-lens reflex camera

The classic Rolleiflex TLR

1957 Kodak Duaflex IV, an inexpensive fixed-focus TLR

A twin-lens reflex camera (TLR) is a type of camera with two objective lenses of the same focal length. One of the lenses is the photographic objective (the lens that takes the picture), while the other is used for the waist-level viewfinder system. In addition to the objective, the viewfinder consists of a 45-degree mirror (the reason for the word reflex in the name), a matte focusing screen at the top of the camera, and a pop-up hood surrounding it. The two objectives are connected, so that the focus shown on the focusing screen will be exactly the same as on the film. However, many inexpensive TLRs are fixed-focus models. Most TLRs use leaf shutters with shutter speeds up to 1/500th sec with a B setting.

Features

Higher-end TLRs may have a pop-up magnifying glass to assist the user in focusing the camera. In addition, many have a "sports finder" consisting of a square hole punched in the back of the pop-up hood, and a knock-out in the front. Photographers can sight through these instead of using the matte screen. This is especially useful in tracking moving subjects such as animals or race cars, since the image on the matte screen is reversed left-to-right. It is nearly impossible to judge composition with such an arrangement, however.

Mamiya's C-Series, introduced in the 1960s, the C-3, C-2, C-33, C-22 and the Mamiya C330 and Mamiya C220 along with their predecessor the Mamiyaflex,^[1] are the only conventional TLR cameras to feature truly interchangeable lenses.^[2] The Mamiya TLRs also employ bellows focusing, making extreme closeups possible.

Rollei Rolleiflex model TLRs have an additional feature for the "sports finder" that allows precise focusing. When the hinged front hood knock-out is moved to the sports finder position a secondary mirror swings down over the view screen to reflect the image to a secondary magnifier on the back of the hood, just below the direct view cutout. This permits precise focusing while using the sports finder feature. The magnified central image is reversed both top-to-bottom and left-to-right.

Advantages

• A primary advantage of the TLR is in its mechanical simplicity as compared to the more common single-lens reflex cameras. The SLR must employ some method of blocking light from reaching the film during focusing, either with a focal plane shutter (most common) or with the reflex mirror itself. Both methods add significant noise to the camera's operation, as well as significant bulk and weight. Most TLRs use a leaf shutter in the lens. The only mechanical noise during exposure is from the shutter leaves opening and closing. Most TLRs are also significantly lighter in weight than a medium format SLR.

• TLRs are different from single-lens reflex cameras (SLR) in several respects. First, unlike virtually all SLRs, TLRs provide a continuous image on the finder screen. The view does not black out during exposure.

• since a mirror need not be moved out of the way the picture can be taken much closer to the time the exposure is actuated by the photographer. This reduced shutter lag is especially advantageous for certain action shots such seen in sports or dance.

• TLRs are also ideal for "candid camera" shots where an eye-level camera would be conspicuous. A TLR can be hung on a neck strap and the shutter fired by cable release.

• Models with leaf shutters within the lens rather than focal-plane shutters can synchronize with flash at higher speeds than can SLRs. The combination of these features are especially advantageous when taking a posed action shot (as, for example, of a martial artist executing a kick or jump) in combination with high intensity electronic flash to freeze the action.

• Owing to the availability of medium-format cameras and the ease of image composition, the TLR is also preferred by many portrait studios for static poses.

• Another advantage of the TLR design can be seen when long exposures are required. During exposure, an SLR's mirror must be retracted, blacking out the image in the viewfinder. A TLR's mirror is fixed and the taking lens remains open throughout the exposure, letting the photographer examine the image while the exposure is in progress. This can ease the creation of special lighting or transparency effects.

Disadvantages

• Few TLR cameras offer interchangeable lenses and none offer the advantages of a zoom lens.
• Because the photographer views through one lens but takes the photograph through another, parallax error makes the photograph different from the view on the screen. This difference is negligible when the subject is far away, but is critical for nearby subjects. Parallax compensation may be performed by the photographer in adjustment of the sight line while compensating for the framing chage, or for highly repeatable accuracy in tabletop photography (in which the subject might be within a foot (30 cm) of the camera), devices are available that move the camera upwards so that the taking lens goes to the exact position that the viewing lens occupied.
• It is not possible to preview depth of field as one can with most SLRs, since the TLR's viewing lens has no diaphragm.

Film formats

The typical TLR is medium format, using 120 roll film with square 6×6 cm images. Presently, the Chinese Seagull Camera and the German Rollei are in production, but in the past, many manufacturers made them. The Ciro-flex produced by Ciro Cameras Inc. rose dramatically in popularity due in large part to the inability to obtain the German Rollei TLRs during World War II. The Ciro-flex was widely accessible, inexpensive, and produced high quality images.^[3] Models with the Mamiya, Minolta and Yashica brands are common on the used-camera market, and many other companies made TLRs that are now classics. The Mamiya C series TLRs had interchangeable lenses, allowing focal lengths from 55mm (wide angle) to 250mm (telephoto) to be used. The bellows focusing of these models also allowed extreme closeups to be taken, something difficult or impossible with most TLRs. The simple, sturdy construction of many TLRs means they have tended to endure the years well. Many low-end cameras used cheap shutters however, and the slow speeds on these often stick or are inaccurate.

There were smaller TLR models, using 127 roll film with square 4×4 cm images, most famous the "Baby" Rolleiflex and the Yashica 44. The TLR design was also popular in the 1950s for inexpensive fixed focus cameras such as the Kodak Duaflex and Argus 75. Though most used medium format film, a few 35mm TLRs were made, the Contaflex TLR being the most elaborate, with interchangeable lenses and removable backs.

The smallest TLR camera is the Swiss-made Tessina, using perforated 35mm film forming images of 14×21 mm.

Notes

1. ^ Www.Tlr-Cameras.Com/Mamiya
2. ^ However, the (6×6 cm) Koniflex (from Konica) is a conventional TLR that has a supplementary tele lens, and the (6×7 cm) Koni-Omegaflex (Konica again) can be used as a TLR with an optional finder and has interchangeable lenses.
3. ^ Mike Roskin, "Occam's Ciroflex," Camera Shopper, May, 1995, 38.

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