Archived posting to the Leica Users Group, 1997/07/27
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On 27 Jul 97 at 0:11, Joe Berenbaum wrote:
> But why doesn't it prevent light from reaching the film in the SL as it is?
> Probably, it moves out of the way when the shutter is fired. Maybe its
> linked to the main mirror and they both move together. If so, then adapting
> a real SL might be impossible- not that I think anyone is seriously
> suggesting that. With a pellicle mirror SLR camera such as the EOS RT, when
> you fire the shutter, the mirror stays put, but the metering sensor or
> secondary mirror- I think it's a mirror, moves out of the way. There is even
Yep, the secondary mirror folds down to the bottom of the mirror
box. In a normal SLR it folds up against the primary mirror.
Btw light losses through mirrors:
A normal SLR with secondary mirror has a reflection/transmission
split of 66/33 (film receives 100% when the mirror is up of course),
a pellicle mirror has a split of 33/66.
This means that only one stop (66/33 = 2x = 1 stop) is lost to the
prism, not 1.4 stop (100/33 = 3x = 1.4 stop).
The mirror in the 1n RS is also much brighter than in the normal 1n
(and also more expensive), so the effect in the viewfinder is hardly
noticeable....but I believe it is harder to focus manually....it can
be retrofitted with other, normal screens.
> >By the time we get to relocating the cell from the bottom of the
> >body into the prism, I'd guess we're up to the price of an R9.
>
> The "R9 Stealth SLR" (as I will now call it ;-}) is a good idea; it could
> have a stationary pellicle mirror and a moving meter mirror and be only a
> little louder than the M6, as the RT is. The RT is quite a camera, and
> (apparently) a lot quieter than the EOS 1N RS. It certainly is in the same
> league as the M6- I've taken hand-held shots with an RT and the subject (a
> friend, five or six feet across the room) wasn't aware that I took a whole
> roll of film, she thought I only took one or two shots. It's not exactly
> silent, but it makes a rather dull sound that isn't very noticeable.
Note that the main difference in sound between the old RT and the
current 1n RS is film transport. The RT also has an option to delay
film transport until after you lift your finger from the release
button, the RS does not (normally!).
Yet Canon has added 19 additional CF options to the 1n, one of
which provides this same transport-delay function (regardless of 1n
or 1n RS). This CF option (only 1 out of 19 can be added) is rather
expensive though, as the update must be done by Canon Service.
PS: for those interested in an overview of these 19 extra CF options,
check my homepage:
http://www.a1.nl/phomepag/markerink/mainpage.htm
- --
Bye,
Willem-Jan Markerink
The desire to understand
is sometimes far less intelligent than
the inability to understand
<w.j.markerink@a1.nl>
[note: 'a-one' & 'en-el'!]