Compiled by Q.-Tuan Luong for the Large Format Page

General information

LF lenses come two ways, ready mounted in a shuter and in barrels with a diaphragm but no shutter. The barrel mounted ones are intended to be used with an external, usually rear mounted shutter. This can be anything from a lens cap (or derby hat in the wet plate days) to the quite complicated Sinar shutter. The most commonly used rear shutter is the one made by Packard, a simple air operated shutter with single speed (aroung 1/20 sec.) and time. Some of these come with a synch contact. These work nicely for strobe on the studio. When a lens comes already in a shutter you get whatever the manufacturer offered at the time the thing was built. Samaller lense typically are in German made Compur shutters, probably the most widely used high quality shutter ever made. Larger lenses will come in Compound or Ilex shutters. Newer lenses come in Copal shutters, which are essentially a Japanese version of the Compur with, perhaps, some improvements. It is really not a matter or choice except that the shutter should be in good condition. Its possible to remount old lenses in new shutters but its expensive (the shutters are expensive) and isn't worth doing unless the lens is something exceptional. Richard Knoppow

If you want to learn a lot about shutters (but NOT ENOUGH to fix one), try to find a copy of L.P.Clerc's "Photography Theory And Practice", Focal Press, 1973 edition. Chapter XVII is all about Shutters (pages 236-271 of that edition). Jean-David Beyer

Linhof invented the shutter in the last century. He split with Deckel and started to make cameras only. Deckel sold the shutter business to Zeiss many decades ago. They put it in the Prontor factory. Deckel went bankrupt in 1995. BobS

Some older shutters

Richard Knoppow

A partial listing of shutters you will encounter on old lenses:

How they work

There are pretty good illustrations in some of the older photography handbooks so a trip to the library is indicated. In general, most leaf shutters are completly mechanical. There have been some designs using electric motors to drive the blades but they have never caught on perhaps because of the need for batteries. The typical shutter is driven by a spring motor. Both helical springs (like a screen door spring) and spiral springs (like a clock spring) have been widely used. Some large shutters also use wire coiled springs. The shutter blades are approximately triangularly shaped. One apex can rotate on a fixed pin connected to the body of the shutter, an opposite apex is connected to a pin on a roatating blade ring. As the ring rotates it moves the blades together or apart. The blade ring is driven by the spring motor. With single action shutters which must be cocked, the cocking action winds or tensions the drive spring. When the shutter is released the spring operates a lever which drives the shutter blades open, it then continues to move a lever which bears on a retarding mechanism. In most shutters made since about 1920, this retarder consists of a clock-work escapement. This retarder keeps the shutter open for a specified time, while it operates and then releases the drive lever so that the main spring can drive the blades closed again. The idea is to open and close the blades as quickly as possible to maximize the efficiency of the shutter. The retarder is adjustable, that's what the speed setting dial does, usually by means of a cam of some sort which limits the distance the retarder is in control of the release lever. Some older types of shutters have an air brake instead of the clock-work. The Dekel Compound is one of these. Compounds were made for at least sixty years and are surprizingly accurate. Some shutters, particularly inexpensive ones, and some very large ones, (Ilex Universal) are "double action" or self-cocking. That means the shutter fires each time the release is pushed whith out having to cock it with a separate lever. This limits the strength of the motor somewhat so that double-action shutters do not have high top speeds. The release lever does the cocking at you operate it to make the exposure. Just as a double action revolver takes a much harder trigger pull than a single action, the double action shutter requires much more force to trip because you are also winding it. As shutters age the speeds often become slower. The slower speeds slow down because of gumming of the lubricant in the retarder clock-work, cleaning will bring them back. At higher speeds the trouble can also be dirt generally increasing the friction, or a drive spring which has become fatigued with use, or both. Often a proper cleaning wil bring the higher speeds back. Shutters must be very clean to operate properly. Also the correct lubricants must be used where lubrication is called for. Typically, very light watch oil is used on retarders and very light MolyKote grease used on sliding parts. Some shutters (Ilex and some others) are intended to run without lubricant and will have irregular speeds if lubricated. The highest speeds of most shutters are calibrated with the assumption that the iris will be wide open. That means the shutter is operating at minimum efficiency. Typically, the actual total open time, as measured by a speed meter will be 15% to 30% slower than the marked speed. The speed spec for late model Synchro Compur shutters require that the top speed of 1/500 measure something like 1/350 to be in spec. Slower speeds are usually more accurate. There have been many designs of leaf shutters over the years. Some older ones had double leafs which rotated completely around and then rotated back the other way the next time the shutter was tripped (Wollensak Optimo). Some shutters use the same leafs for both diaphragm and shutter, opening only to the specified f/stopm (Bausch & Lomb Volute). This arrangement is used in some modern automatic exposure control cameras. But most between-the-lens shutters operate as described above. The best illustrations I know of are all in rather old books. Check for C.B. Neblette's _Handbook of Photography_ or the even older Henney and Dudley book of the same name. Your library should be able to get them through inter library loan if they don't have them. A couple of pictures will make things much clearer.

Table of older aperture systems

Scanned by David Stein

Packard Shutters

by Richard Knoppow

Packard shutters go back to the 1890's. Most of them are air operated, the shutter being operated by an air cylinder on the back of the shutter and actuated by squeezing an air-bulb connected by a rubber hose. Three versions of Packards were made: The first has only "bulb" exposure, i.e. stays open until you close it, the second has a pin that selects between bulb and instantaneous ( about 1/20sec) exposure and the third kind has two bulbs, one for B and one for I. Some shutters of the last two kinds have contacts for syncronizing flash. I have occasionally seen other versions with a solenoid instead of the air cylindar for driving the shutter.

The Packard can be mounted either in back or in front of the lens. The most typical use is to mount the shutter on the back of a lens board with the air hose brought out through either a hole or a fitting going through to the front. The shutter is held in place with four wood screws, very simple. Some Packard shutters offer either bulb or instantaneous exposure controlled by a pin which projects through the front of the lens board. when the pin is pulled out, the shutter is opened by squeezing the bulb and stays open until the blades are sucked back with the same bulb. In instantaneous the pin is pushed in. When the bulb is squeezed a toggle arrangement pushes against the pin and the shutter opens and closes with the same squeeze. Maximum shutter speed is dependant on how hard you squeeze but practically is about 1/20th sec, also dependant on the size of the shutter. Packard shutters can also be mounted on the front of a lens by means of a baffle and clamp. None are sold commercially but the design will be obvious when looking at a shutter. The electric shutters have more consistant speed but are more expensive.

Packard shutters are limited in what they can do but are very much cheaper than a standard shutter and the cost of re-mounting a lens. For a great many purposes they work just fine. Its possible to mount a Packard on lens board which is fitted to take lenses in smaller boards or with an iris-diaphragm lens holder. That way any number of lenses can be used on same shutter. Packard shutters can be made in very large sizes and are often the only practical way to have a shutter for some lenses (e.g. the 16" Kodak Portrait lens). The largest stock unit has a clearance of 7". Packard shutters are still made. They are avaiable from:

Professional Photographic Products Inc.
117 Vine Street P.O.Box 0169
Hammonton, NJ, 08037-0169
Packard is still in business. The number is 800 257 8541

[R. Miller: see also Equinox Photographic They used to stock them, but as of 10/2005 seldom have them. ]

They will send you a free catalogue which includes replacement parts for old shutters. Typical prices are along these lines No.6 (T&I)shutter 3" opening, $102 without synch,$137 with synch. Used packards are getting hard to find. I used to buy them for $10 or $20 for non-synch ones. Its pretty easy to makeshift a synch using a microswitch mounted on the back of the lens board and actuated by the air cylinder.

By Dion Johnson

Packard shutters are self cocking. Generally, they have two operation modes - B and I. The I "instantaneous" setting causes the shutter to both open and close with one squeeze of the bulb. The speed varies on how hard you squeeze the bulb, how flexible is your rubber tubing, and how big is the shutter. It's difficult to get enough consistency to feel confident of exposing your color transparency film with one of these. The B vs I operation is usually accomplished by inserting a approx .060" pin into the mechanism, which causes the final part of the travel of the piston to close the shutter. In original configuration, this little pin mounts in a small bushing and has stops when it slides in and out of the hole. Typically, the air hose, and this pin extend out to the front of the lensboard. They come in many sizes from about 3x3" up to 6x6", maybe more. They are very easy to clean and refurbish, and tend to give long service. They respond well to graphite and silicone. Usually, the Packard shutter has black felt on its front surface, and mounts to the back of your camera's front standard with 4 screws, just smaller than the bellows frame. Some Packard shutters have flash sync... it's very easy to add this with a momentary microswitch if you are handy. Just mount the microswitch inside the Packard metal housing so it is tripped when the shutter is wide open. It's feasible to mount a Packard shutter in front of your lens... you need a slip-on flat plate to hold the shutter, something like an overgrown Cokin filter adapter. Of course, if you are going to mount something in front, why not go ahead and get a more modern, real shutter and stick it on there.

Sizes are given as follows for models 5 (time only) and 6 (time
and instantaneous):
opening diameter               overall dimensions
1.5"                           3.25x3.25"
1.75"                          3.5x3.5"
2"                             4x4
2.25                           4.5x4.5
2.5                            4.75x4.75
2.75                           5x5
3                              5.75x5.75
3.25                           6x6
3.5                            6.5x6.5

Modern shutters: Copals, Compurs and Prontors

by Bob Salomon

As to the difference between a Copal and a Compur shutter: Compur has 1/3rd step click stops on the aperture, Copal has none. Compur has a stop at the end of the aperture scale, Copal does not. Compur can add an aperture setting device to allow setting the aperture from behind the camera. Compur does not. The Compur may have a faster top speed depending on the shutter size. As to pricing the Compur is more than 2x the price of the Copal so, in some sizes, it may double the price of a lens. Also available for current lenses are the Rollei Linear Motor shutter for view camera lenses, the Horseman ISS shutter, the Noblex shutter and the Sinar shutter. The most common ones are the Copal, Compur and the Prontor Professional.

Copal 0 = 1 sec. to 1/500, no aperture click stops, no remote aperture control
Copal 1 = 1 sec. to 1/400, no aperture click stops, no remote aperture control
Copal 3 = 1 sec. to 1/125, no aperture click stops, no remote aperture control

Compur 0 = 1 sec. to 1/500, 1/2 stop aperture click stops, no remote aperture control
Compur 1 = 1 sec. to 1/500, 1/3 stop aperture click stops, remote aperture control available
Compur 3 = 1 sec. to 1/250, 1/3 stop aperture click stops, remote aperture control
(Remote control units for the aperture allow swtting the aperture from behind the lens).

Prontor Professional 01S = 1 sec. to 1/250, disengageable 1/3 stop aperture click stops, remote aperture control, remote shutter control
Prontor Professional 1S = 1 sec. to 1/250, disengageable 1/3 stop aperture click stops, remote aperture control, remote shutter control
Prontor Professional 3S = 1 sec. to 1/125, disengageable 1/3 stop aperture click stops, remote aperture control, remote shutter control
(On the Prontor professional, with its accessory remotes, aperture and shutter speed can be set from behind the camera, the shutter can be opened to taking aperture to check DOF, open aperture for focusing and closed down to taking aperture with shutter closed for firing the shutter. The cable release can be attached directly to the remote control unit.)

Today the thread size for the lens cells of all 0, 01, 1, 3 shutters from Copal, Compur, Prontor, Noble, Horseman, Rollei and Seiko are identical as are the thread sizes to attach them to the lens boards. Old shutters from various manufacturers varied the sizes but today they are standardized as are the lens cell thread sizes.

by Jean-Christophe Barnoud

dimensions in mm                     Copal 0            Copal 1      Copal 3
1/board mounting thread               M32.5x0.5        M39x0.75       M61.0x0.75
2/flange ring diameter                 34.6                 41.6      64.0
3/board hole diameter                  34.8                 41.8      64.2
4/front lens cell thread               M29.5x0.5        M40.0x0.75   M56.0x0.75
5/rear lens cell thread                M29.5x0.5        M36.0x0.75   M56.0x0.75
6/front to rear cells flange          20.0 +-0.025     20.0+-0.025   28.6+-0.025
(M32.5x0.5 means : diameter 32.5mm, length of one thread 0.5mm = 2 threads per
mm = roughly 50 tpi, angle 60 degrees)
This refers specifically to Copals. Post WWII Compurs are the same except for tolerances concerning the front to rear lens cell flanges distance (anyhow measured shutters show that practical manufacturing tolerances are much smaller than specs). Prontor shutters are also the same except that there is a "01" size which is an hybrid of "0" lens cells and "1" flange mount. Finally I left over all exotic sizes as "00", "2", "4" and "5" as those came (as prewar "0", "1" and "3" shutters) in a variety of thickness, diameters and threads.

Well, I have not conducted tests on those Prontor shutters so I could not tell you if they are more precise than the Copals. They seem quite well made though. What is sure however is that they offer some unusual features like :

You can also buy a nice system with a command box and two cable releases to automate all this but the price is a bit extreme ...

Prontor-Werk Alfred Gauthier GmbH is a company of the Zeiss Group. They make shutters, accessories and cable releases for photographic or industrial use under the brand Prontor as well as shutters and accessories under the brand Compur. The current address in Germany is:

Prontor Werk Alfred Gauthier GmbH
      Gauthierstr. 56
      75323 Bad Wildbad
      Tel.: Int + 49-7081 7811
      fax. (49) 7-081-781467

On 27 September 1996 they sent a catalog:

This brochure lists 7 models of Compur shutters as currently available :
Compur 0 (ref 1 800 504) 1s to 1/500 + B, 1/2 f stop clicks, no remote
control of aperture
Compur 1 (ref 1 145 098) 1s to 1!500 + B, 1/3 f stop clicks, optional
remote control of aperture
Compur 3 (ref 1 146 203) 1s to 1/200 +B , 1/3 f stop clicks, optional
remote control of aperture
Compur electronic m0 (ref 1 018 009) 32s to 1/125 + T
Compur electronic m1 (ref 1 141 009) 32s to 1/125 + T
Compur electronic m3 (ref 1 142 002) 32s to 1/60 + T
Compur electronic m5 (ref 1 143 004) 32s to 1/30 + T

There are also 5 models of Prontor shutters (excluding behind the lens
shutters) :
Prontor press 0 (ref 1 012 006) 1s to 1/125 + B+T
Prontor press 1 (ref 1 112 008) 1s to 1/125 + B+T
Prontor professional 01s (ref 1 190 434) 1s to 1/250 + B (beware size 0 for
lens cells, size 1 for flange)
Prontor professional 1s (ref 1 190 345) 1s to 1/250 + B
Prontor professional 3 (ref 1 190 205) 1s to 1/125 +B

Interestingly, I also have the same (same reference, same date) with the mention :
Exclusive USA Representative GEISS-AMERICA, INC.

Comments on the Prontor by Tuan

Update: The Prontor Professional was discountinued in 2001.

With a self-cocking shutter, when you are making multiple exposures, you might be able to avoid touching the camera (that's assuming you use same f-stop and speed), resulting in a better chance to get a perfect registration. This is often done in architectural photography for instance, in order to mix lights. Another advantage of having a self-cocking shutter is when you have these odd exposures of 2 or 3 seconds, where it is somewhat difficult to time with good repeatability. you can just do several times 1 second.

The use of the remote control is optional. Otherwise, the Prontor needs two ordinary cable releases. Those cable releases need to be equiped with the ability to lock them at a position, otherwise critical functions are difficult to perform. One is used like on any other shutter. The other is used to switch between the different shutter modes: open full aperture, open real aperture, closed. This is similar to the switch on the Copal, except that the Copal provides only open/closed.

I used to have a Prontor on my 110. I liked the ability to time precisely and repetitively 2-3 second exposures, as well as the possibility to switch instantly between having the lens opened at full aperture, opened and stopped down, and closed ready for shooting.

However, I think those advantages are outweighted by the drawbacks:

In conclusion, I found that while the Prontor was very nice to operate, it was not simple and reliable enough for use in the field. As my Prontor became rusted, I eventually got my 110 remounted in a Copal.

The timing test of a Copal #1 by Jean-David Beyer shows that mechanical shutters are very accurate:

Indicated       Correct         1       2       3       4       5      6       7       Average
1               1               0.92522 0.92269 0.92419 0.92401 0.92558 0.92678 0.92518 0.924807
   1/2             1/2          0.50192 0.50174 0.49964 0.50206 0.50244 0.50041 0.50054 0.501250
   1/4             1/4          0.25826 0.25545 0.25450 0.25204 0.25384 0.25420 0.25276 0.254436
   1/8             1/8          0.12839 0.12814 0.12966 0.12763 0.12745 0.12718 0.12765 0.128014
   1/15            1/16         0.06786 0.06863 0.06758 0.06796 0.06811 0.06868 0.06873 0.068221
   1/30            1/32         0.03382 0.03383 0.03401 0.03485 0.03404 0.03500 0.03338 0.034133
   1/60            1/64         0.01520 0.01455 0.01468 0.01483 0.01478 0.01484 0.01476 0.014806
   1/125           1/128        0.00754 0.00763 0.00746 0.00739 0.00761 0.00747 0.00762 0.007531
   1/250           1/256        0.00369 0.00381 0.00379 0.00387 0.00385 0.00381 0.00384 0.003809
   1/400           1/409        0.00269 0.00276 0.00274 0.00266 0.00274 0.00276 0.00271 0.002723

1,2,3,4,5,6,7 are the measurements (in the order measured at each speed).
This should allow you to compare their average speeds and get an idea
of the variations.

More info