"David Nebenzahl" <nobody@[EMAIL PROTECTED]
> wrote in message
news:47cb51f0$0$15624$822641b3@[EMAIL PROTECTED]
> On 3/2/2008 3:35 PM Richard Knoppow spake thus:
>
>> The usual reason for rejecting the Speed Graphic is
>> weight, the Crown is lighter and has a shallower box.
>> However I do find the focal plane shutter to be useful
>> especially for barrel type lenses. Also, Crown Graphics,
>> originally the economy model, are often more expensive
>> than the Speed Graphic on the used market.
>> Either will give you a taste for LF although they
>> have very limited movements and limited bellows draw.
>> Graphic cameras were intended to be hand held and offer a
>> way of getting a large negative for situations where a
>> tripod can not be used.
>
> (Like that famous picture of Jack Ruby shooting Oswald,
> where at least one handheld Graflex is visible.)
>
> Since we're on the subject, yes, I should have mentioned
> about the barrel lenses, though these are more rare than
> lenses with shutters.
>
> Questions:
>
> 1. I didn't know that Crowns go for more than Speeds. Is
> this because people like the former better, or for other
> reasons (see question #2)?
>
> 2. Do Speed Graphics typically have working focal-plane
> shutters? I would have thought that because of the
> complexity of this mechanism, it might be likely to fail
> in cameras of this age. (I've never even seen a Speed
> Graphic up close and personal.)
I don't know what prices are like now but a few years
ago Crown Graphics were going for more than Speed Graphics.
One has to check the shutter, maybe even to make sure
its still there (some idiots like to remove them). Actually,
the Graflex shutter mechanism is very simple and not easily
broken. The shutter curtain in the later cameras appears to
be made of some synthetic with quite long life. Usually they
need only to be lubricated.
I don't remember if the Graflex site has a diagram of
the shutter. If so it will make things obvious.
The first shutter used by Folmer & Schwing on the
Graflex SLR was a self capping shutter but it proved too
elaborate and not reliable so, within some very short time,
they came up with the simplified shutter used forever after.
This consists of a rubberized cloth curtain with five slits
of varying length on it. The curtain runs between two spring
loaded rollers, quite similar to the rollers used for window
shades. The lower roller has a spring which can be adjusted
by winding it. This changes the travel time of the shutter.
The upper roller has a fixed spring with enough tension to
maintain the curtain taught. The speed is set by winding the
curtain up to the upper roller to the slit desired. The
spring on the lower roller is wound to the desired tension.
There is a chart on the camera showing the shutter speeds
resulting from each combination of slit width and spring
tension. There is enough blank space between each slit and
the next to cap the film. When the shutter is tripped the
curtain winds down one slit and stops. You must then put the
dark slide back in the holder because when the shutter is
wound up again it pulls the slit back over the focal plane.
If you trip the shutter a second time without winding it
back the _next_ slit will go over the film.
Because the curtain accelerates as it travels the speeds
are not constant from top to bottom. The amount of change
varies with the tension and slit size being greatest for the
highest speeds where it can be nearly 2:1 over the travel.
At one time F&S advertized this as an advantage for Graflex
cameras because it would darken the sky in a landscape. The
last of these shutters, the one used on 4x5 Pacemaker Speed
Graphics, had a flywheel to control the speeds on the low
range which resulted in considerably more uniform exposure.
The _effective_ speed of a focal plane shutter is a
function of the distance between the shutter slit and the
film and the focal length of the lens. Actually the angle of
the cone of light emitted by the lens so it varies with the
focus. In the Graflex/Speed Graphic shutter the efficiency
is not very high so there is considerable variation plus the
higher speeds can not be directly measured with a shutter
tester. The speeds will read low. The speed can be read more
accurately by adjusting the intensity of the light at the
tester so that its just one stop more than the point at
which the tester stops counting. One then reads the light at
the half intensity points. For Speed Graphics the measured
speed of the highest speed, 1/1000 second will be only about
1/800th if this method is not used. I've found several SGs
where the shutter tension adjustment had been wound very
tight to get the top speed to read 1/1000 on a total open
time tester. This, of course, will throw off all the speeds.
The shutter in the Pacemaker Speed Graphic and the
Super-D Graflex are pretty accurate, most of the 25 speeds
listed on the charts for other Graphic and Graflex cameras
have a good deal of wishful thinking in them.
Like 35mm rangefinder cameras its possible to burn a
hole in the focal plane shutter by pointing the camera at
the sun with the shutter wound.
Note also that careful adjustment of the stops for the
shutter is necessary to avoid shutter bounce at the end of
travel. This can lead to a strip of double exposure at the
bottom of the negative. It is a more difficult problem in
Graflex cameras with rotating backs because of the about 20%
longer shutter travel needed to cover the film lengthwise.
Once a Graphic or Graflex FP shutter is set up and lubed
correctly it won't need attention for many years.
There have been more elaborate FP shutters on 4x5
cameras. One is the shutter found on some Busch Pressman
cameras. These, I think were intended to meet the military
spec for the Speed Graphic. These are self-capping shutters
cut out the light when they are re-wound) and have more
accurate and uniform speeds. I've never seen a drawing of
the mechanism and have, in fact, only ever seen one camera
with this shutter. They were advertized along around the mid
1950's. The other elaborate shutter is the one used on the
ICA, later Zeiss-Ikon Mirroflex. This is a gear train
regulated shutter with some resemblance to the shutter in
the Contax camera. Also self-capping and quite accurate. The
main problem with these is rubber rot necessitating
replacement of the shutter curtains.
I am quite sure this is much more than anyone ever
wanted to know about these shutters.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]
|
