Copal Press shutter: No aperture scale!!

[Niels Alpert]

Hi.

Thanks for reading my post.

Recently bought a used 4x5 lens. It's a Schneider Symmar S in a Copal
Press number 0 shutter. The trouble I'm having is due to the fact that
there are no f stop markings on the shutter. Why the manufacturer should
do that, I have no idea. I could calculate the stops myself with a spot
meter and some patience, but I would rather contact Copal directly, if
that's possible, and ask if they could provide me with the proper
aperture scale for this shutter. There is a tiny metal plate over which
a tiny indicator needle moves when you adjust the aperture. This plate,
I presume, ordinarily has the aperture scale, but for some reason, on
this shutter, that plate is simply black.

Do any of you out there have any experience with unmarked shutters like
this? What is the easiest solution?

Thanks in advance for any help you can offer.

Jason

[Bob Salomon]

Whenever you buy a new shutter it has no calibrated aperture scale. The
calibrated scales are sold by the lens manufacturer rather than by the
shutter manufacturer.

This is because a lens has to be calibrated so the aperture scales are
accurate and the shutter manufacturer has no idea as to the max/min aperture
of your lens and the number of possible scales can be astronomical.

You can also have any good camera repairman calibrate the scales for you or
you can do it your self by metering through your groundglass (after
determining the light loss from your groundglass/fresnel screen).

No manufacturer did anything in this case. Someone remounted the lens in a
new shutter.

HP Marketing Corp. U.S. distributor for Amazon, Braun, Gepe, Giottos, GO
Light, Heliopan, HP Combi Plan T, Kaiser fototechnik, KoPho cases, Linhof,
Pro Release, Rimowa, Rodenstock,Sirostar 2000

----------

[peter]

Hi,
the shutters always will be deliverd with an empty
scale and will be engraved by the lens company.
Possible the shutter from your lens is not the
original one.
Ask Schneider you can have a scale.
Peter

Niels Alpert <nie...@loop.com> schrieb im Beitrag
<35CEB1...@loop.com>...

[skgrimes]

The reason that the iris scale on your shutter is blank is that different
lenses require different iris scales. Original iris scales are supplied by
the *lens manufacturer* not the shutter manufacturer (Copal)

In cases where it is inconvenient to obtain a scale from the lens
manufacturer, such as obsolete lenses or odd installation I can supply any
engraved iris scale needed -- no exceptions. I need both the lens and the
new shutter, and/or the old shutter/barrel on hand to do this.

My web-site has more details and pictures of iris scale engraving. SKG

--
--- S.K. Grimes -- Feinmechanik ----

--Machine work for photographers
--Lenses fitted to shutters, iris scales engraved
http://www.skgrimes.com
(updated 8-5-98)

Niels Alpert wrote in message <35CEB1...@loop.com>...

[David L. DuPuy]

Niels Alpert wrote in message <35CEB1...@loop.com>...
>Hi.

>Recently bought a used 4x5 lens. It's a Schneider Symmar S in a Copal
>Press number 0 shutter. The trouble I'm having is due to the fact that

>there are no f stop markings on the shutter. > < snip >

As a rough indication of f-stop, you might use a millimeter scale and simply
measure the aperture size. The definition of f-stop is that of

focal ratio = (lens focal length) /
(aperture diameter)

The focal length is fixed, and the effective diameter (and hence the f-stop)
changes as one closes down the aperture. Hence, a 50mm (focal length) f/2
lens should have a one-inch aperture when wide open. If you experiment
yourself, it won't have the look of engraved f-stops, but there is some
satisfaction in understanding what you've got.

(for email, remove the 'XXX') David

[Frank Filippone]

Thanks David for the info, but I don't get the equation you listed....
Is this how it works?

Aperture Diameter = Focal Length / Fstop

In the example given..... Aperture Diameter = 50MM / F2 = 25 MM or 1 inch

If I had a 450 MM lens with maximum Aperture of F12.5 ( anyone note a Fuji
450-C Here?)
Then the aperture would be 450MM/12.5 = 36MM ( about 1.5 inches )

If I close down to F45, the aperture size would be 450MM/45 = 10 MM

Now do I have it straight?
--
Please do not auto-respond. Please respond to address below.

Frank Filippone
red...@worldnet.att.net

[Richard Knoppow]

"Frank Filippone" <red...@worldnet.att.net> wrote:

Hi Frank, The aperture diameter will be affected by the
magnification of the lens elements. Its easy to measure its effective
size. Simply set up a point sourc (like an illuminated pin hole) at a
long distance from the lens, 20 feet is enough for this lens. Place a
sheet of paper or ground glass over the front of the lens, with the
light source at the back. The diameter of the illuminated circle of
light will be the effective diameter of the stop. Find its size when
the lens is wide open, then devide this size for smaller stops. Set
the diaphragm by measuring it on the screen and mark whatever you are
making the stop scale out of. You can pretty much assume that the
clear diameter of the illuminated circle with the diaphragm wide open
is the marked maximum f/stop.
You can also do this by autocolimating. Put the lens on a camera.
Place a small flashlight against the back near the center. Place a
mirror over the front of the lens (first surface is best but a shaving
mirror will work OK). Focus the lens until a sharp image of the light
spot on the ground glass is produced near where the flashlight is.
The lens will then be effectively focussed for infinity. Using the
same flashlight against the ground glass as the light source for
measuring the diaphragm diameter. This is effectively the same as a
light at infinity.
---
Richard Knoppow
Los Angeles, Ca.
dick...@ix.netcom.com