The camera binocular reflex (TLR) has a higher goal for reflex viewfinder and another lower for the shooting. The case is made of two separate bedrooms. The upper chamber has a mirror reflecting the image on a large frosted glass put in the shade for framing. Aiming is done with the camera at chest height and the image is reflected upside down in the left-right direction. The focus is on the frosted sometimes with a retractable magnifier for more precise adjustments. Because of two separate bedrooms, the image will not disappear at the onset as in the SLR. Both objectives are grouped and placed on the same plate of development so that it is simultaneous. A parallax error existed initially but was later corrected by a tilting system of sight of the optical related to the development.

The first LRT plates dating from 1885 but it’s mostly from 1939 that the LRT film achieved success with the contribution of modernity Rolleiflex of the German firm Franke & Heidecke.

The TLR camera was making square format views in 6 X 6 cm and rarely in 4 X 4 cm rollfilm. One of the undeniable advantages of this format is its size that requires smaller enlargements and thus a greater fineness of grain in favor of the quality of the print. The competitors of this time were the 35 mm rangefinder (eg Leica and Contax) but from a different, more expensive format. TLRs were built until the late 60. Reporters and serious amateurs used this type of aircraft until the '50s, a period that corresponds to the arrival of the monocular reflex (SLR). Some brands will even develop the benefits of SLR in favor of the film 120/220 as used in TLR...

'TWIN LENS REFLEX' cameras (93)