Focal Plane Shutters

All DSLRs have focal plane shutters. As we all know, at a certain
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

"Gary Eickmeier" wrote:
All DSLRs have focal plane shutters. As we all know, at a certain 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?

Yes and nog.

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

In article ,
"David J. Littleboy" 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.

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

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 nog.


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

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.

On Sun, 27 Aug 2006 07:17:44 -0700, stauffer wrote:


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 nog.


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

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.
That was usually vertical focal plane shutters as in a couple of the old
exactas.
--
Neil
Delete l to reply

wrote in message
ups.com...

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 nog.


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

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

Some DSLRs use both focal plain curtain for speeds less than 1/1000 and
an electronic shutter for higher speeds.

Gary Eickmeier wrote:
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

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.

--
Frank ess

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

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.