Twin-lens reflex Twin-lens reflex cameracamera

Twin-lens reflex cameraTwin-lens reflex camera A A twin-lens reflex cameratwin-lens reflex camera ( (TLRTLR) is a type of ) is a type of cameracamera with with

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

FeaturesFeatures

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

AdvantagesAdvantages

A primary advantage of the TLR is in A primary advantage of the TLR is in its mechanical simplicity as its mechanical simplicity as compared to the more common compared to the more common single-lens reflex cameras. The SLR single-lens reflex cameras. The SLR must employ some method of must employ some method of blocking light from reaching the film blocking light from reaching the film during focusing, either with a during focusing, either with a focal plane shutterfocal plane shutter (most common) (most common) or with the reflex mirror itself.or with the reflex mirror itself.

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

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

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

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

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

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

DisadvantagesDisadvantages

Few TLR cameras offer Few TLR cameras offer interchangeable lenses and none interchangeable lenses and none offer the advantages of a zoom lens. offer the advantages of a zoom lens.

Because the photographer views through one Because the photographer views through one lens but takes the photograph through another, lens but takes the photograph through another, parallax error makes the photograph different parallax error makes the photograph different from the view on the screen. This difference is from the view on the screen. This difference is negligible when the subject is far away, but is negligible when the subject is far away, but is critical for nearby subjects. Parallax critical for nearby subjects. Parallax compensation may be performed by the compensation may be performed by the photographer in adjustment of the sight line while photographer in adjustment of the sight line while compensating for the framing chage, or for highly compensating for the framing chage, or for highly repeatable accuracy in tabletop photography (in repeatable accuracy in tabletop photography (in which the subject might be within a foot (30 cm) which the subject might be within a foot (30 cm) of the camera), devices are available that move of the camera), devices are available that move the camera upwards so that the taking lens goes the camera upwards so that the taking lens goes to the exact position that the viewing lens to the exact position that the viewing lens occupied. occupied.

It is not possible to preview depth of It is not possible to preview depth of field as one can with most SLRs, field as one can with most SLRs, since the TLR's viewing lens has no since the TLR's viewing lens has no diaphragm. diaphragm.