photography gear 3 - the single reflex camera

a single lens camera (slr) is basically a camera that uses a system that captures the light through a mirror and a prism that directs the light to the viewfinder. the mirror is at a 45% angle, allowing it to direct the light vertically toward the prism but when the photographer presses the shutter release, the mirror flips upward to let the light go directly to hit the film. the term 'reflex' comes from the reflection of the mirror system used to redirect the light. it was an ingenuous invention that allowed the photographer to view exactly the image that is passing through the lens and is captured on film.

the pentaprism situated on the roof of the camera sits on the optical path between the mirror and the viewfinder. it reflects the light several times to make up for the initial inversion caused by the lens. if you would look at the image directly through the lens, it would appear upside down.

the path of light in a single lens reflex camera

the single lens reflex is further development form the earlier cameras that used to have two light paths. one for the viewfinder and one that goes straight through the lens to hit the film. since the camera had two lenses they were referred to as twin-lens reflex (tlr). the major drawback of those cameras, in addition to bulk was, that since you have two light paths, they were not sharing the same optical path. though that wasn't too noticeable on medium and long range, at a short distance, parallax used to cause some framing errors, especially in close-up photography.

long before digital, we used to shoot film. pictured here is the pentax k1000, a middle range camera from the now defunct asahi pentax who was a major player in the photography industry