With an automatic, instant return mirror, the viewfinder blackout time might be as short as th second.

Well-integrated focal-plane shutter, instant return mirror and pentaprism design.

Well-integrated, durable and reliable design without instant return mirror, but with excellent auto-diaphragm interchangeable lenses and large accessory system.

In 1958, Minolta introduced its SR-2 single lens reflex (SLR) 35mm camera which was equipped with a bayonet mount and instant return mirror.

The F combined every SLR technological advance available in 1959 (automatic diaphragm lenses, instant return mirror and eyelevel pentaprism viewfinder) into one package.

Asahiflex IIB (Japan; called Sears Tower 23 in USA): first SLR with reliable instant return mirror.

Mechanical camera-to-lens linkages can link auto-diaphragm lenses and instant return mirror, focal-plane shutter SLRs, but electronic autofocus required additional electronic data exchange between camera and lens.

Gamma Duflex (Hungary): first instant return mirror SLR, first metal focal-plane shutter SLR, first internal semi-automatic lens diaphragm SLR.

Digital photography did not alter the basic focal-plane shutter, instant return mirror, pentaprism, auto-diaphragm lens, TTL meter, autoexposure and autofocus formula of SLR camera design developed over the previous century - except, of course, it is filmless.

In 1960 the Model B had a name change and became the Edixa-Mat Flex Model B, the word Reflex being shortened to Flex, and it featured shutter speeds from 1/25 to 1/1000 of a second, the instant return mirror, automatic aperture actuation and interchangeable viewfinders.

Although today live view has limitations (unintelligibility in bright sunlight, image lag with moving subjects, rapid battery drain, etc.), its perfection, plus an electronic shutter, would make the bulky and expensive precision mechanisms and optics of a focal-plane shutter, instant return mirror and pentaprism unnecessary and allow the camera to be a completely electronic device.