Focal Plane Shutters
Gary Eickmeier
shutter speed, the flash sync speed, the shutter begins performing its
exposure time by just passing a slit across the focal plane, as opposed
to a leaf shutter, which opens and closes for that specific period of
time. For example, at 1/1000th the shutter may traverse the focal plane
at the usual speed, say 1/200th, but be only 1/5 of the frame wide while
doing it.
So my question is, is that really stopping the action in the same way
that a leaf shutter is doing? If you shot a hummingbird with a focal
plane shutter, would it stop the wings or would we just see 1/200th of a
second of them? Is a focal plane shutter really as fast as it is marked?
Gary Eickmeier
David J. Littleboy
Yes and no<g>.
The exposure at any one point on the film/sensor really is 1/1000, and it'll
stop motion at that point just as a leaf shutter would (of course, leaf
shutters usually only go up to 1/500, but that's a minor detail).
But, if the motion extends for a larger area, the film will record what's
happening at different times at different places on the film. The standard
demonstration of this is shooting a propeller plane head on while the
propeller is operating; you get a surrealistically twisted propeller.
David J. Littleboy
Tokyo, Japan
Bob Salomon
"David J. Littleboy" <dav...@gol.com> wrote:
> leaf
> shutters usually only go up to 1/500, but that's a minor detail).
Except Rollei versions that go to a true 1/1000.
--
To reply no_ HPMarketing Corp.
Gary Eickmeier
Jim Townsend wrote:
> Focal plane shutters can introduce distortion. As you say, the
> slit takes much longer to move than actual exposure time.
>
> Here's a link to a site where a fellow did some test shots of
> a high speed object. (A wheel on a Dremel tool). You can
> see the results.
>
> http://webs.lanset.com/rcochran/flash/hss.html
Good example. Proves my point, that focal plane shutter speeds are not
really that fast. The "high speed sync" mode of some cameras is nothing
more than the flash going off many hundreds of times per second for the
duration of the traverse of the shutter. It does not produce an action
stopping exposure any more than a daylight exposure.
I still want to see a photo of a hummingbird with a focal plane shutter
at various speeds.
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?
Gary Eickmeier
stau...@usfamily.net
David J. Littleboy wrote:
>
> > So my question is, is that really stopping the action in the same way that
> > a leaf shutter is doing? If you shot a hummingbird with a focal plane
> > shutter, would it stop the wings or would we just see 1/200th of a second
> > of them? Is a focal plane shutter really as fast as it is marked?
>
> Yes and no<g>.
>
>
> happening at different times at different places on the film. The standard
> demonstration of this is shooting a propeller plane head on while the
> propeller is operating; you get a surrealistically twisted propeller.
>
> David J. Littleboy
> Tokyo, Japan
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.
Neil Ellwood
That was usually vertical focal plane shutters as in a couple of the old
exactas.
--
Neil
Delete l to reply
JohnR66
news:1156688264....@h48g2000cwc.googlegroups.com...
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
George K
an electronic shutter for higher speeds.
Frank ess
> <stau...@usfamily.net> wrote in message
> news:1156688264....@h48g2000cwc.googlegroups.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.
--
Frank ess
ASAAR
>> 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.
If you camera could trip the shutter at several different shutter
speeds with the lens removed you'd see immediately what the problem
was. There's only a moving slit at the highest speeds. I noticed
this back in the early 60's, but don't recall if I was looking at a
Nikon F's titanium shutter, or a cloth shutter on either a Leica
(unlikely) or a Zorki (more likely). I don't know how many noticed
this (since nobody commented) but one of the recent Nikon D80
announcements mentioned that instead of using a combination
electronic and focal plane shutter, it will employ only a vertically
moving mechanical focal plane shutter. It also doesn't synch. with
flashes at speeds as high as some other Nikon bodies allow.
irwell
wrote:
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!
EO
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:
Gary Eickmeier
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
ASAAR
> 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
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
Tuli
Neil Ellwood
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.