Traditional DSLRs rely on the mirror located in front of the sensor to reflect light to the focusing screen and from there to the viewfinder. The mirror used is 100% reflective (meaning it’s opaque). When the shutter button is pressed, the mirror flips up and the actual exposure is made; during the exposure, as the mirror is flipped up there is no light being reflected back towards the focusing screen or the auto focus sensors. As a result the viewfinder blacks out and auto focus sensor also stop receiving any information during that time.
Secondly the mirror which is located so close to the sensor inside the camera body causes vibrations when it moves up and down. This could cause a similar effect like that of camera shake and cause pictures to look shaky or blurry.
Thirdly if this mechanism is altogether eliminated the camera’s operation would become much simpler and faster and the physical size of the camera (depth) could also cut down considerably.
Translucent mirror technology
Recently Sony, another pretty big player in the digital imaging world has come up with a revolutionary new product called ‘translucent mirror technology’. Instead of a flapping mirror they now employ a translucent mirror which is a fixed one. What it does is to reflect approximately 1/3rd of the light to the phase detection auto focus sensor and let the rest 2/3rd of light to pass on to the image sensor.
Advantages of Translucent Mirror Technology
The advantages of this system over conventional mirror system are many.
The camera’s viewfinder does not go black during an exposure meaning you get to see exactly what you are shooting.
Similarly the camera’s auto focus sensor receives 100% of the information, without any blackouts, which is extremely helpful in situations that require continuous focusing.
Lack of a flapping mirror means less vibration enabling you to handhold at even slower shutter speeds than traditional DSLR cameras.
As there is less mechanical parts to think of cameras using translucent mirror technology is capable of achieving Faster frame rates than their mirrored counterparts.
Disadvantages of Translucent Mirror Technology
Now let’s discuss what could be the downside of such a system.
The major concern photographers raise is; the efficiency of such a camera system rests on the quality or resolution of the LCD screen inside of the electronic viewfinder.
The performance of this technology under low light, wet and dusty circumstances could be assessed only in actual field-work.