Give me wings to fly..... Digital photoshoot of a flying oldtimer

Most SLR cameras permit upright and laterally correct viewing through use of a pentaprism situated in the optical path between the reflex mirror and viewfinder. Light is reflected by a movable mirror upwards into the pentaprism where it is reflected several times until it aligns with the viewfinder. When the shutter is released, the mirror moves out of the light path and the light shines directly onto the film, or in the case of a DSLR, the CCD or CMOS imaging sensor.

Digital photoshoot of a flying oldtimer

Prior to the development of SLR, all cameras with viewfinders had two optical light paths: one path through the lens to the film, and another path positioned above ( TLR or twin- lense reflex) or to the side ( rangefinder). Because the viewfinder and the film lens cannot share the same optical path, the viewing lens is aimed to intersect with the film lens at a fixed point somewhere in front of the camera. This is not problematic for pictures taken at a middle or longer distance but parallax causes framing errors in close-up shots. Moreover, focusing the lens of a non-reflex camera when it is opened to wider apertures (such as in low light or while using low-speed film) is not easy.

A flying "dinosaur" - digital photoshoot of the russian Antonov

The single-lens reflex (SLR) camera uses an semi-automatic moving mirror system which permits the photographer to sometimes see exactly what will be captured by the film or digital imaging system, as opposed to pre-SLR cameras where the view through the viewfinder could be significantly different from what was captured on film.