Non-mechanical shutters

Has any progress been made on this kind of thing yet? Something like
on/off
opaque LCD windows that could be used as shutters instead of metal
ones?
-Rich

In article .com,
Rich wrote:
Has any progress been made on this kind of thing yet? Something like
on/off
opaque LCD windows that could be used as shutters instead of metal
ones?

What about the Pockel's cell? That has been around for a *long*
time, and it is probably less likely to introduce problems at the fine
image resolution level than a LCD shutter.

But any electro-optical shutter has one disadvantage: It can't
protect the focal plane sensor when it is powered off and the camera is
rested on a table or whatever, and the sun moves into the file of view.

For that matter -- what is to protect the e-o shutter *itself*
from such damage?

Nikon, at least (and probably many others) uses a mechanical
shutter in front of an electro-optical (which I *think* is simply
electronically disabling the storage cells in the sensor until the
actual moment of exposure, and re-disabling them while the image is
shifted out through the amplifiers and such.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

I've been meaning to ask about this ...

When selecting *EXTREMELY* short exposure times (say 1/4000) is this really
all being done mechanically? I'm having trouble believing that something
mechanical can operate that fast, lat alone let in an even amount of light
during that time.

Am I missing something here?

Cockpit Colin wrote:
I've been meaning to ask about this ...

When selecting *EXTREMELY* short exposure times (say 1/4000) is this
really all being done mechanically? I'm having trouble believing that
something mechanical can operate that fast, lat alone let in an even
amount of light during that time.

Am I missing something here?

With film SLRs and some dSLRs the shutter curtains move at a
fixed speed above a particular shutter speed (often about 1/250th).
At lower shutter speeds the front curtain opens and the rear
curtain follows some time later. At higher speeds both curtains
move together with a gap between them. The size of the gap sets
the exposure time. With some dSLRs an electronic shutter takes
over at the higher speeds.

Re-reading that, I haven't explained it very well. Googling "focal
plane shutter" should turn up a better description.

-Mike

Mike Warren wrote:
Re-reading that, I haven't explained it very well. Googling "focal
plane shutter" should turn up a better description.

Yes it does. Here's the first match.

http://www.mir.com.my/rb/photography...ch/focalplane/

-Mike

In message ,
"Cockpit Colin" wrote:

I've been meaning to ask about this ...

When selecting *EXTREMELY* short exposure times (say 1/4000) is this really
all being done mechanically? I'm having trouble believing that something
mechanical can operate that fast, lat alone let in an even amount of light
during that time.

Am I missing something here?

The total exposure time is much longer than 1/4000; the shutter opens as
a slit at the higher speeds, and moves across the frame. Each pixel is
only exposed for 1/4000s, but different pixels are exposed at different
times as the slit moves across the frame.
--


John P Sheehy

"Martin Trautmann" wrote in message
...
1/20000 could
be expected nowadays, while no one needs such times ;-)

I do. I'm trying to capture one of lifes must elusive moments - my daughters
room in a tidy state, followed closely by one of mother and daughter not
arguing!

On Mon, 22 Aug 2005 10:41:40 -0700, Rich wrote:

Has any progress been made on this kind of thing yet? Something like
on/off
opaque LCD windows that could be used as shutters instead of metal
ones?

These have been around, since the late 40's or 50's. IIRC, they were
called quantum shutters, had no moving parts, were optically triggered,
and were originally developed to photograph the above ground nuclear bomb
tests in Nevada.

I think Harold Edgerton, an MIT physicist, was involved in their
development. (FWIW, Edgerton is the father of the high speed electronic
flash that we take so much for granted today.) He, along with two other
scientists, formed the company EG&G (the "E" is Edgerton), to design
and build cameras and shutters to take extremely short duration
(millionths of a second) exposures of nuclear detonations or anything
that happens really fast.

Stefan

In article , wrote:
In message ,
"Cockpit Colin" wrote:

I've been meaning to ask about this ...

When selecting *EXTREMELY* short exposure times (say 1/4000) is this really
all being done mechanically? I'm having trouble believing that something
mechanical can operate that fast, lat alone let in an even amount of light
during that time.

Am I missing something here?

The total exposure time is much longer than 1/4000; the shutter opens as
a slit at the higher speeds, and moves across the frame. Each pixel is
only exposed for 1/4000s, but different pixels are exposed at different
times as the slit moves across the frame.

As already mentioned elsewhere in this thread -- it depends on
the camera with digital cameras (which is what we should be discussing
in this newsgroup). Some may have a purely mechanical shutter, while
others have a mechanical shutter which opens, and then the
electro-optical one at the sensor determines the actual exposure time.

Back in the film cameras, it was always a traveling slit above
certain shutter speeds (which was the maximum shutter speed which could
be used with electronic flash).

Some shutters traveled horizontally, while others traveled
vertically. (I know that my Miranda F used rubberized cloth as shutters
which traveled horizontally. The Zeiss Contax has an all-metal shutter
which resembles a roll-top desk which travels vertically. I believe
that the Nikon-F had a horizontally traveling shutter, while the
lower-budget Nikon of the same period had a vertically-traveling all
metal shutter, the "Copal Square", IIRC.

Depending on the kind of shutter travel and the situation, this
could result in interesting effects.

Take a photo out the window of a very fast traveling car while
passing a power pole with the Contax, and you will wind up with a tilted
pole -- along with anything else of appreciable vertical dimension.

Take a photo out the window of a very fast traveling car with
the Miranda, while passing one going in the other direction, and you
will get one of two possible effects.

In the US, you will get a stretched-out image of the car, as its
image is traveling in the same direction as the shutter curtain slot.

In the UK, you will be shooting out the other window, and the
image will be compressed compared to the background (which will be
somewhat compressed, but not as much.)

Of course -- all these effects only are visible when the shutter
speed is quite high. Say, at a minimum, 4 times the highest shutter
speed for electronic flash sync.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
Stefan Patric wrote:
On Mon, 22 Aug 2005 10:41:40 -0700, Rich wrote:

Has any progress been made on this kind of thing yet? Something like
on/off
opaque LCD windows that could be used as shutters instead of metal
ones?

These have been around, since the late 40's or 50's. IIRC, they were
called quantum shutters, had no moving parts, were optically triggered,
and were originally developed to photograph the above ground nuclear bomb
tests in Nevada.

I think Harold Edgerton, an MIT physicist, was involved in their
development. (FWIW, Edgerton is the father of the high speed electronic
flash that we take so much for granted today.) He, along with two other
scientists, formed the company EG&G (the "E" is Edgerton),

FWIW -- the other two were Germsheusen and Greer. (I'm not sure
of the spelling of the first 'G'. :-)

to design
and build cameras and shutters to take extremely short duration
(millionths of a second) exposures of nuclear detonations or anything
that happens really fast.

I think that was the Pockel's cell -- with the primary
disadvantage for our use that it was rather thick.

IIRC, it was a pair of crossed polarizers, with a birefringent
crystal between them. A high voltage applied to the crystal rotated the
plane of polarization, thus "opening" the shutter. As it had no moving
parts, it could be switched in a very short time -- purely up to the
electronics design.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---