Tuesday, September 11, 2012


While looking at cameras on the web yesterday, I came across a blatantly false claim by Sony.  They wrote about the Sony Alpha DSLR camera:

"This changes everything.
Shoot with unprecedented speed and precision thanks to Sony's revolutionary Translucent Mirror Technology™. While traditional DSLRs depend on a reflex mirror to flip up and down with every shot, Sony's award-winning technology changes all that with its fixed-position, translucent mirror design…"

That statement is definitely false.  The first camera incorporating such a design was the Canon Pellix.  The Pellix was first marketed in 1965. It was Canon's first 35mm Focal-Plane Shutter SLR Camera with TTL metering.  It was also the first commercial production SLR that incorporated a fixed pellicle mirror. It employed a super-thin, semi-transparent film only 20/1000 mm thick that was used as a fixed mirror.

The Leica connection to all of this is the fact that the Leica Visofelx III was also available with a pellicle mirror.  This was a special modification by Norman Goldberg.  Goldberg is perhaps best known, in the Leica world, as the creator of the Camcraft N-5 electric motor drive for the Leica M2 and MP. However, also to his credit were several other inventions for Leicas and other cameras. The clip he designed to permit wearing an M Leica on the belt was widely used.  He also offered a modification of the Visoflex reflex housing, involving either a prism or a pellicle mirror.

Pellicle mirrors never reached any nominal success; the main reason being that part of the incoming light is permanently diverted to the viewfinder, effectively lowering the speed of the lens in use.  In addition, these mirrors are quite delicate and very difficult to clean.  Cleaning, on the other hand, is important because any dust, smudges or other dirt would adversely affect image quality since the mirror is in the lightpath from the lens to the film or sensor.

In view of this is seems strange that Sony would even market a camera of this type and it is equally strange that they have to accompany it with obviously false claims.


  1. Conventional flip up and down mirrors in SLR and DSLR cameras have proven to be quite reliable. It seems silly for a company to make use of a pellicle mirror these days and then accompany their advertising with false statements.

  2. One of the main reasons for Canon to introduce the pellicle mirror in 1965 was to eliminate vibrations from the mirror flipping up. To this day, many companies use a spring loaded mirror which, when released, simply slaps into a small piece of foam rubber for dampening. That indeed introduces a fair amount of vibrations. These are of no consequence with everyday photography. But high magnification photos, as in close ups and long telephoto work is definitely influenced by that. Leica solved this problem with the introduction of the original Leicaflex by incorporating a cam drive for the mirror. The mirror movement was activated by a cam that initially accelerated the mirror but then slowed it down to the point that it settled with virtually no movement at its uppermost position. That very much eliminated any vibrations. There is a simple vibration teat one can conduct. Set the camera on a level surface and then place a nickel on the camera sitting on its edge. Place it as close to the prism housing as possible because that is closest to the mirror. Then release the camera with a cable or electronic release. The majority of SLR/DSLR cameras will have enough vibrations to tip the nickel off its edge.

  3. I think that the ever improving quality of electronic finders will make conventional DSLR mirrors obsolete in the not too distant future.

  4. I tried your nickel vibration test with my cameras. You are right, the nickel fell over each time I fired the camera. I have no Leica R cameras for comparison, but my old Nikon F failed miserably as did a friends Canon FTb.