What’s to Come: Translucent Mirror Technology

Since the release of the Canon 5D Mark II back in August 2005, there has been a dramatic shift in ideologies when it comes to selecting camera packages for a given project.  However, with the introduction of video in these low cost/low impact cameras, people have been able to capture a stunning image, without breaking the bank.  Recently, Sony reintroduced a technology using a Translucent Mirror to capture the digital image (first introduced by Canon in the 60′s).

How it Works:

In essence, a portion of the light from the lens filters through the mirror component and hits the imaging sensor at the back, which records the picture. At the same time, the mirror would reflect another part of the light upward to another sensor for phase detection autofocus (AF).

Why this is Cool

Since there are no moving mirror components in the dSLR’s, there is no blackout time. This lets users view the scene and anticipate what might happen for the next shot. This is good for sports photographers who may miss an important moment while the mirror moves up and blocks the view.

Press Release

According to Sony, the translucent mirror helps to reduce the size and weight of the camera. This is because the conventional optical pentaprism used in dSLR’s has been replaced by an electronic viewfinder.

• Continuous phase-detection autofocus even during video, live view or continuous shooting mode
• Lack of camera shake due to mirror movement
• No viewfinder blackout while taking photograph
• Shorter shutter lag
• Exposure, White Balance, and other settings can be easily and directly verified on the electronic viewfinder (and thus tweaked) before taking a picture.
• More compact body

Downfalls

One distinct disadvantage of using such a mirror is that the view through the optical viewfinder is dimmer than an SLR using a traditional mirror system.

• Lack of optical viewfinder – Digital Viewfinder…
• Less light reaching sensor, due to portion of the light being reflected to phase-detection auto-focus array
• Refresh rate limited by the time it takes the sensor to form an image; in low light this causes severe stuttering of the viewfinder image when panning
• No real-time viewfinder update at high shooting rates, the viewfinder shows the last picture taken instead of where the camera is actually pointed; mostly a concern with fast-moving subjects.
• The EVF has far less dynamic range than the sensor, so the EVF does not properly show what will be captured.
• Over a period of time, the mirror surfaces can become soiled. As a result of this the mirror scatters the light rays and degrades the recorded image.

Until we see that camera, it is hard to tell if the new technology will fix the downfalls of dSLR’s but we sure hope it does!  Although the images do look stunning from dSLR’s, if used in the wrong hands, can produce some very nasty imagery (moire, aliasing, etc).

What this Means for dSLR’s

Sony’s use of Pellicle mirrors in these two dSLRs is a sign that the company is serious about the dSLR business and is ready to take on bigger players like Canon and Nikon. It may also mean the firm could be preparing for a professional dSLR using this mirror, too.