Why doesn t the back screen on my EOS digital camera display a live video preview?
Unlike point and shoot digital cameras, Canon EOS digital cameras are SLRs, which means they use mirrors. The image sensor is situated behind the mirror, so no light reaches the image sensor normally but is instead deflected up into the viewfinder. When a picture is taken the mirror flips up out of the way, blacking out the viewfinder and letting light reach the image sensor. Using this design means there is traditionally no way to have live image previews on the rear screen of the camera and have a working optical viewfinder at the same time, since the mirror is normally down and blocking the light path to the image sensor. Canon (and other makers of digital SLRs) have historically designed their cameras this way since digital SLRs are meant to appeal to the same sorts of people who bought film SLRs and want their digital cameras to work the same basic way as film cameras. There are also technical reasons why live image previews are tricky with digital SLRs.
Your camera is an older or lower-end EOS digital camera, which lacks support for Live View video. Unlike point and shoot digital cameras, Canon EOS digital cameras are SLRs, which means they use mirrors. The image sensor is situated behind the mirror, so no light reaches the image sensor normally but is instead deflected up into the viewfinder. When a picture is taken the mirror flips up out of the way, blacking out the viewfinder and letting light reach the image sensor. Using this design means there is traditionally no way to have live image previews on the rear screen of the camera and have a working optical viewfinder at the same time, since the mirror is normally down and blocking the light path to the image sensor. Accordingly, Live View cameras have a video mode which flips up the mirror and feeds live video to the rear LCD. This means, of course, that the viewfinder is blacked out when Live View is on. It also means that the camera has to be able to transfer a massive amount of
