DSLR camera live view

The main reason why DSLR camera could not live view  is a complex internal system within the camera. DSLR cameras use a mirror  that prevents the entry of images to the sensor BEFORE the photo was taken. So the charge of measuring light and the focus is specific modules that are under the mirror, while we see an image through the prism over there in the mirror When the shutter button is pressed, the mirror up momentarily so that the sensor receives the image and record it, while the module and the prism turns experiencing a blackout So the live-view at that time did indeed seem impossible because the sensor is blocked by the mirror
 Even when the auto focus video recording equipment also can be made quickly and have never imagined before.The advantage of live-view with a transparent mirror is a DSLR camera can perform a live-view (displays an image that will be photographed or recorded video through the LCD screen) while the camera still rely on phase detection autofocus system with AF module. This is very practical, with no need to use two sensors, but still able to avoid the use of contrast detection auto focus time-based live-view is slow as all the working principles of conventional live-view.