While looking at cameras on
the web, I came across a blatantly false claim by Sony. They wrote about the Sony Alpha SLT cameras:
"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…"
The Sony SLT mirror
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 beam splitter or a pellicle mirror. These too preceded Sony for a long time.
Leica camera with pellicle mirror Visoflex and Camcraft N-5 electric motor.
Please note the missing release lever and mirror action adjustment knob on the right side of the Visoflex
Please note the missing release lever and mirror action adjustment knob on the right side of the Visoflex
Pellicle mirrors never
reached any nominal success; the main reason being that part of the incoming
light is permanently diverted to the viewfinder, or in the Sony SLT cameras
where part of the light is reflected to the phase detection autofocus system. This effectively lowers 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 light
path 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.
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Reader Ketil Are Haugsand wrote: - remembering the Pellix well - with the noisy clack (!) of any mirror in the sixties and seventies, we had great expectations, in principle.. but, agh.. how fast it disappeared!
ReplyDeleteDark viewfinder and reduced speed - well, exactly!
I realize that Sony offers continuous auto focus with this system. But it seems too much of a price to pay for little, if any, gain. After all, other autofocus systems seem not to have any problems, so why give up viewfinder brightness and lens speed?
ReplyDeleteConventional 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.
ReplyDeleteOne 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.
ReplyDeleteI think that the ever improving quality of electronic finders will make conventional DSLR mirrors obsolete in the not too distant future.
ReplyDeleteYes, indeed. Mirrorless cameras have arrived and appear to be here to stay.
Delete