DEAR RICHARD ET ALIA,
Well, I sit corrected! I thought I recalled that the Grafmatic holders
held 8 sheets but you are right! They hold 6. They work perfectly in my Speed
Graphic. It is nice to have fewer holders and less weight when back packing.
CHEERS!
BOB
On April 3, 2019 at 10:58 PM `Richard Knoppow <dickburk@xxxxxxxxxxxxx
mailto:dickburk@xxxxxxxxxxxxx ;> wrote:
Graflex accessories are described at the Graflex.org site.
The Grafmatic is a holder which contains six sheets of
conventional sheet film, each in a septum. The septa (?) are made
of thin sheet metal with the sides folder over to form channels
which hold the film. The are in a case which looks like a thick
sheet film holder with a handle on the side. When the handle is
pulled out and pushed back in the septum at the front is moved
around to the back and a fresh one comes to the front. When all
are used the mechanism locks.
The Grafmatic is intended for use in the Graflok back. It
generally will not fit a standard sheet film back because it is
too thick. Also, it should be locked in because the motion of
changing films tends to pull it out. I have several and have used
them but prefer standard holders. It is important that the septa
be straight, no kinks or bends and the edges should be lubricated
with wax. If they are hard to move they will jam or become bent.
Filters are interesting. The idea that putting a filter in
back of the lens is a bit of a myth but one that is often
repeated. A filter should be located where the light going
through it is as collimated as possible. That means for a lens
with a fairly distant object it should be on the front or distant
side of the lens. The idea is that the closer to parallel the
light rays going through it are the less effect it has on the
aberration of the image. A plane parallel glass will produce both
spherical aberration and chromatic aberration if the light going
through it is not parallel and on axis. This is due to the
deviation of the light rays going through surfaces that are not
perpendicular to the rays. Of course, the thickness is also
important; the thinner the filter the less it produces
aberrations. If a filter is used behind the lens, where the light
rays are at an angle, a thin gelatin filter _must_ be used. On
the front of a lens focused, say on infinity, the thickness and
index of refraction has little effect.
It surprises some people that a plane flat sheet can produce
aberrations. In fact, there are lenses that use such plane
surfaces as part of the correction.
A glass plate will also produce internal reflections (flare)
if not treated. A gelatin filter also produces all these effects
but because it is usually very thin and usually has in index
close to air, the effects are very small.
In general a filter should be used on the side of the lens
with the least convergence or divergence of the light rays. It
should also be as thin as possible and have an index of
refraction as close to air as possible.
On 4/3/2019 7:33 PM, Zack Widup wrote:
> > Grafmatic is a type of film holder. I never used one but I've
seen them around.WB6KBL
Fred Picker said the preferred type of filter to use with a view
camera is a gelatin sheet placed behind the lens. He outlined a
sort of "Z" shaped piece of metal strip with one end mounted on
the lens board with a small screw. That steel strapping strip
they used to use to hold crates shut during shipping was the
ideal stuff to use. The other end sticks out beyond the lens but
outside the range of the lens (it doesn't block the view). Wrap a
layer of electrical tape around it to prevent scratching the filter.
Then get a small magnet with a piece of electrical tape around it
or a piece of rubber flexible refrigerator magnet. Use the magnet
to hold the filter sheet in place in back of the lens.
I've been using these for many years (decades). I'm very careful
with my filters and none have a scratch on them.
I also carry a handful of trash bags with me to put over the
camera in case it starts raining. I''v had good luck with not
getting my wooden camera wet.
You can use whatever you want for the lens board as long as it's
sturdy.. Aluminum just happens to be easy to work with. I like
the 6061 alloys.
Zack
> dickburk@xxxxxxxxxxxxx mailto:dickburk@xxxxxxxxxxxxx
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