Live-view on digital SLR cameras currently already becoming more common, in contrast to three or four years ago in which none of the DSLR camera that can display picture to be taken on the LCD screen (call it a preview or a live-view). At that time DSLR users only get a peek at the image through the optical viewfinder and it is commonplace since the days of film cameras. The problem is, many people new to the camera since the digital age by looking at the image directly through the LCD screen and wondered why an expensive digital SLR cameras just can not live-view.
The main reason why DSLR camera could not live-view (at the time) is the complexity of internal systems within the camera. DSLR cameras use a mirror (mirror) that prevents the entry of the image to the sensor BEFORE the photos were taken. So, in charge of measuring light (metering) and sets the focus is specific modules that are under the mirror, while we see an image through a prism that is in top mirror (see illustration above – the yellow is the mirror). When the shutter button is pressed, the mirror momentarily lifted the sensor receives the image and record it, while the module and the prism turns experiencing blackout (due to obstructed mirror). So the live-view at that time did indeed seem impossible because the sensor is blocked by the mirror.
The concept of live-view is simple (and conventional) and then introduced by the camera manufacturers like Canon and Nikon DSLR with a mirror BEFORE lifting techniques photos were taken. This means that the image of the lens directly into the sensor is blocked by a mirror so that it can be instantly displayed on the LCD screen. But the consequences of this technique is the closing of the metering module and the module as a live-view AF. Yet the greatness of the DSLR camera is on a fast auto focus (based on phase detection) and if the AF module is closed does it mean when a live-view we lose the ability to fast AF. In return, auto focus when the live-view contrast detection system uses a slow, not unlike like the AF system on a non DSLR camera, even as the camera phone.
Different breakthrough brought by Olympus (E-330) and Sony (A300/350 and A500/550), which offers a dual sensor system. The first sensor is the main sensor to record images, while the second sensor is a special live-view sensor (see illustration above). The aim is to phase detection-based auto focus can still be used when the live-view. To activate the live-view, the available levers that change the position of sliding mirror such that the direction of the image from the lens of live-view sensor. Users can switch from live-view mode into normal mode (shooting through the viewfinder) and vice versa with ease, simply move the lever earlier.
Lack of a system like this is a live-view sensor as an additional sensor displays only about 90% coverage, it is very less even still less than the optical viewfinder coverage. Because of the size and quality of additional sensors is not as good as its main sensor, then some important things can not be done during a live-view, such as assistance to an enlarged image to focus manually, without the overlay graph (histogram or grid), and can not even preview their work stabilizernya sensors installed in the main. Not to mention the cost of production increased because of using two sensors simultaneously.
Increasingly bright future of hope when Sony once again rumored to be making a breakthrough, revolutionary live-view DSLR pellix presenting the plan that supposedly will be named Alpha A55 and A33. What is DSLR pellix (pellicle mirror)? This term is no other states use a mirror (mirror) of a semi-transparent (translucent) so that at the same time, images can be forwarded from the lens directly on the sensors and modules at a time can be reflected to the metering and AF modules. The only thing missing from DSLR pellix is a prism, so the viewfinder for the camera of this type uses an electronic viewfinder camera like EVIL (Electronic Viewfinder Lenses interchangeable) or mirrorless camera. Semi-transparent mirror is actually not new considering this kind of mirror is used also in the world of intelligence (spies) as in Hollywood movies.
Advantages live-view with a mirror that is transparent is a DSLR camera can perform a live-view (displaying the image that is photographed or recorded video over the LCD screen) while the camera auto focus system still relies on phase detection by AF module. It 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. Even the auto focus while recording video are also still can be made quickly and have never imagined before.
