Focal Plane Shutters

On Sun, 27 Aug 2006 08:28:08 -0700, "Frank ess"
wrote:

JohnR66 wrote:
wrote in message
ups.com...


snip


Another common attribute of focal plane shutters is the creation of
a
"leaning into motion" when the shutter slit traveled vertically.
Early pictures of racing cars were good examples. This became
almost an icon of speed, and even comic strip illustrators drew
fast
moving objects tilted. Wheels went from round to ovals tilted in
direction of motion. This effect was magnified by the slow speed of
the film in those days. In daylight photograhy with a vertically
moving focal plane, the distortion is still there but is so small
as
to be unnoticable with today's films.

The effect was pronounced because of the relative slow speed of the
traveling slit. Modern multi bladed focal plane shutters are
relatively fast with some syncing with flash units at 1/250th or
more
of a second (full open).
John

I figured the vertical-slot shutter in my film SLR of the early 80s
should be able to show that leaning-wheel phenomenon, if oriented
portrait style at slow shutter speeds. Spent a nice roll of Kodachrome
25 without demonstrating the effect. If I could find the slides, maybe
my eye would work better on a scanned example, and I could see
something. Otherwise, a disappointing attempt.
The old Houghton Butcher Ensign reflex camera I owned during the
1940s had the xposure controlled by both the slit being adjustable,
and the spring tension on the shutter release also being adjustable.
Attained an astonishing 1/250th second!

See the Olympus E10/20 - Mechanical aperture but electronic shutter.
Sequence - "Shutter" open, 1/2 press to lock distance and aperture, Full
press to CLOSE "Shutter" and process image and flush imager, "Shutter
open to max aperture (or preset).



Gary Eickmeier asked:

But the real question is, does digital permit the possibility of
electronic shutters that work entirely differently from either type of
mechanical shutter? Don't some amateur cameras work by exposing
electronically? Grabbing the data over a reduced period of time? Does
that cause shutter lag, in order to flush the sensor before letting it
fill back up again for the exposure? Any camera engineers out there?

EO wrote:

See the Olympus E10/20 - Mechanical aperture but electronic shutter.
Sequence - "Shutter" open, 1/2 press to lock distance and aperture, Full
press to CLOSE "Shutter" and process image and flush imager, "Shutter
open to max aperture (or preset).

OK I have an E20, and I thought it was purely a leaf shutter situation.
It only goes up to 1/640th of a second, and it flash syncs at any speed.

Let's see... it has the possibility of live preview, and the viewfinder
image comes thru a prism ahead of the imager... that means it has to be
wide open during viewing, then when you press the shutter it has to
close down to shooting aperture and expose the imager. I suppose it
could be either closing down completely before exposure, or just closing
to shooting aperture and exposing electronically. All I know for certain
is that there is very little shutter lag, and the shutter is silent.

Gary Eickmeier

On Sun, 27 Aug 2006 20:56:32 -0400, Bill wrote:

The Nikon D50 has a mechanical shutter that only reaches 1/90 then the
electronic "shutter" of the CCD takes over for higher speeds.

The Nikon D70 has a mechanical shutter that only reaches 1/250 then the
CCD takes over.

The Nikon D80 has a fully mechanical shutter that reaches up to 1/4000.

Flash sync is 1/500 for the D50 and D70, and 1/200 for the D80. But the
D50/D70 models cheat by using the CCD "shutter" to get this high, which
can introduce some nasty image artifacts.

High speed flash sync is possible on all models up to their rated top
speeds 1/4000 or 1/8000 using compatible flash units.

Thanks for that information.

EO wrote:

Gary - It closes and then calculates the exposure (electronic). Remember
the only time the viewfinder is blanked is immediately after you full
press the shutter and then it immediately opens up again. Note that at
slow shutter speeds (1/2 sec or longer) the finder is blanked longer -
shorter speeds you don't notice it.

Ed


Gary Eickmeier wrote:

I suppose it could be either closing down completely before exposure, or
just closing to shooting aperture and exposing electronically.

Gary - It closes and then calculates the exposure (electronic).
Remember the only time the viewfinder is blanked is immediately after
you full press the shutter and then it immediately opens up again. Note
that at slow shutter speeds (1/2 sec or longer) the finder is blanked
longer - shorter speeds you don't notice it.

Ed


Gary Eickmeier wrote:

I suppose it could be either closing down completely before exposure, or
just closing to shooting aperture and exposing electronically.

On Mon, 28 Aug 2006 14:25:22 -0800, EO wrote:

Gary - It closes and then calculates the exposure (electronic).
Remember the only time the viewfinder is blanked is immediately after
you full press the shutter and then it immediately opens up again. Note
that at slow shutter speeds (1/2 sec or longer) the finder is blanked
longer - shorter speeds you don't notice it.

Ed


Gary Eickmeier wrote:

I suppose it could be either closing down completely before exposure, or
just closing to shooting aperture and exposing electronically.
I don't suppose many people remember the slr before the introduction of
the instant return mirror, that was one of the reasons I bought a Miranda
D when it became available (around 1960 IIRC). After slrs that stayed
blank after exposure it was an enormous advance that doesn't sound very
good when just written down but was a revolution in use.

--
Neil
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