re-shuttering lenses

It is often cheaper, quicker and easier to stick an old lens with a defective shutter into a new (or at least, recycled) shutter than it is to have the existing shutter repaired. It's very easy, because shutters are amazingly standardized (albeit in a range of sizes) but there is slightly more to it than just pulling the cells off one shutter and sticking them onto another. The main things to watch out for are lens cell spacing and aperture calibration.

On the other hand, we'd be remiss if we didn't mention www.lens2shutter.com, acknowledged experts in professional re-shuttering.

shutters

The sizes normally encountered are 00 (very small), 0 (small standard), 1 (large standard), 2 (obsolete and almost impossible to get repaired nowadays), 3 (the largest common size), 4 and 5 (very big and very rare). Overwhelmingly the most common are 0 and 1; nowadays, only a few big lenses use 3.

 

compur 00

 

compound 4

Shutter sizes

The shutter on the left is a Synchro-Compur 00; on the right a Compound we believe to be a No. 4. Both are mounted on identical-sized Linhof Technika lens panels. We had to make up a flange (the bright metal ring) to fit the 00 because we did not have any panels with a small enough hole. The No. 4, on the other hand, is the biggest shutter that can be fitted to this panel.

Most of the figures given below are taken from various shutters in our possession but are only indicative as there have been variations over the decades. Bear in mind that many retaining rings are stepped, so you need a bigger hole than minimum; typically about 2-3mm bigger.

Asterisked figures are from other sources. Our measurements and different web-sites do not always agree. For example, the thickness of a no. 3 is variously reported as 26.75 and 28.64mm. It way well be that standardization is limited: measuring a given shutter is the only realistic possibility.

Size

Minimum lens panel hole size

Thickness

Lens cell thread diameter

Maximum clear aperture

Remarks

00

25mm

16mm

22.5mm

16.5mm

No way of holding the shutter open during focusing: must use 'B' and a locking cable release

0

33mm

20mm

29.5mm

22mm

For most modern lenses up to about 135mm

1

39mm

20mm

40mm F/36mm R

29mm

For most modern lenses 150-360mm

2

63mm

25mm

44.5mm

35mm

Obsolete, hard to repair and not fully standardized

3

not known

around 27mm*

56mm*

34-35mm*

Used on very big or very long modern lenses such as the Schneider XXL series

4

76mm

around 40mm*

67mm

45-50mm

Seldom encountered

5

not known

Around 60mm*

83-86mm*

65mm

Very rare indeed

shutter makes, sizes, reliability and accuracy

There have been countless leaf shutters over the years, from Compur, Prontor, Copal, Seikosha, Ilex, Kodak and many more. Most tend to match the above sizes fairly closely, though variations of a millimetre or two in any dimension are nothing unusual. And some seem to be unique.

In our experience over 40 years, the most reliable seem to be old Compurs and Compounds (Compounds are pneumatically governed, Compurs, mechanically) from before the mid-60s. These seem to survive complete neglect for decades. If they need cleaning, this will usually put them back in good order for decades more. Prontors, later Compurs, Copals and Seikoshas may need cleaning more often (every decade or two) but are still astonishingly reliable. Other shutters tend to gum up faster, unless they are very simple, preferably with only a limited range of speeds.

It's almost always the slow speeds that gum up first, though they can often be brought back by sluicing out with trichloroethane or a similarly aggressive solvent (be careful, and remove the lens cells first) or even by simple exercise.

Maximum speeds on all leaf shutters are normally optimistic: reckon that 1/500 is likely to be at best 1/350 and quite possibly closer to 1/250, while 1/250 is often 1/200 or so. From 1/15 to 1/125 will usually be pretty good, then 1/8 to 1 second may be more or less sluggish. With mechanical (not pneumatic) shutters you can usually hear the bad ones, though, with a sort of hiccuping buzz instead of a smooth whirr. Just occasionally (especially with Compounds and other air-governed shutters) the slow speeds may be fast instead of slow.

 

 

compound dagor

Goerz Dagor in Compound shutter

Compounds are incredibly reliable as long as they are clean. The tube at the top is the pneumatic damper: the shutter speed setting dial is in front of it, hence the term 'dialset'.

After cocking the shutter (the big lever on the right) wait five seconds for the air pressure to equalize before firing (small lever top left, next to cable release socket). The shutter does not need to be cocked for 'B' (Brief/Bulb) or 'T' (Time, sometimes 'Z' for 'Zeit')), only for 'I' (Instantaneous -- sometimes 'M' for Moment). I-B-T (or M/B/Z) are set via the little nub just above the diaphragm scale.

 

 

copal press

Copal Press No. 1

You can clearly see the scallops here, with the locking screw at the bottom. This may or may not be an official way of changing the shutter thickness, but it works. 'Press' shutters do not need cocking; the penalty is a lower top speed, typically (as here) just 1/125 second.

lens cell spacing

Obviously, the thickness of the shutter determines how far apart the lens cells are held. To achieve the right separation, the usual choices are shims or by changing the thickness shutter body. The former may have been lost with old lenses in which case your only hopes are finding a lens that has never been apart (or at least, which has been put back together again properly) or finding the correct separation from the manufacturers' data sheets (often on the web) or elsewhere.

The easiest way to ensure correct spacing is via the overall front-to-back dimensions of the lens, which is usually given to 1/100mm (and is likely to be a round-ish sort of number anyway. Working to 1/50mm (0.02mm) should be more than enough to ensure that your re-shuttered lens is at the right separation.

 

changing the thickness of the shutter

On the Copal-Press illustrated on the left there are 12 notches or scallops on the ring concentric with the front cell mount. Undo the screw, and the scalloped ring can be unscrewed somewhat. It is not clear whether this is a deliberate feature to allow fine-tuning of the thickness, from a minimum of 20mm up to a maximum of more than 20.5mm, or a by-product of the design.

aperture calibration

If the shutters are identical, with one in working order and the other not, it is easiest to transfer the diaphragm plate from one to the other. If they are not absolutely identical (e.g. two Compur-Rapids) you need to check the size of the diaphragm at each stop, and if need be, engrave a new diaphragm scale. This need not be outstandingly elegant (see the illustration above) and can be done with a Dremel tool and and engraving bit. You may be able to remove an existing, marked aperture scale; turn it over; and engrave the blank side. As you can see from the picture above and below, they are normally held on with two screws.

Note that older shutters often have non-linear scales, i.e. the apertures are widely spaced at the full-aperture end but get closer and closer together at the small-aperture end, while later shutters are more likely to have equidistantly scaled aperture markings. The crudely-engraved Copal above is equidistant; the Compound below, non-linear, so f/6.8 and f/8 (1/2 stop) are further apart than f/45 and f/64.

Of course, if you don't mind the delay and expense, you can probably find a repairer who will do this for you, at which point it should look prettier but you might as well have had the old shutter repaired...

compound dagor scale

the locating pin

Most new shutters are provided with a little locating pin beside the rear threaded portion, a couple of millimetres from the thread. This is to stop them rotating in the panel. Many photographers remove these and throw them away, relying on the friction of the locking collar to hold the lens in place. This also allows the lens to be 'screwed in' without using a lens spanner. If at all possible, though, the pin should be left in place. Use a small ward file to cut a locating slot, if drilling is too much hassle (as it usually is).

re-shuttering 'up' and 'down'

It is often possible to put a lens into a larger shutter than was originally used: you need a pair of adapter rings, each with a female thread for the lens cell and a male thread for the shutter. If you have to pay full commercial rates for this, it rarely makes sense, but if you can do the necessary lathe-work yourself or if you have a kind friend with a lathe, it may be a good idea.

Re-shuttering into a smaller shutter often requires more work and you are quite likely to lose the maximum aperture: anything from 1/3 stop to 1 stop, though of course a lot depends on the focal length and design (to say nothing of the precise location of the diaphragm). It should be possible to re-shutter our 270/5.5 Tele-Xenar from its broken dial-set Compur No. 2 (illustrated on the left) into a Copal No. 1, for example, but the maximum aperture attainable would be about f/6 or f/6.3, so a Compur 3 would be better. But we don't have a Compur 3 and we do have a Copal 1.

 

compur dialset

 

barrel ross

 

 

shuttering barrel lenses

Armed with the correct overall length of the barrel lens and the thickness of the shutter body, and assuming you can unscrew the lens cells from either end of the barrel, you should have a pretty good idea of whether you can put a barrel lens into a given shutter or not.

Even if the lens is very compact, like the 73/8 inch Ross illustrated (it is little more than an inch, 25mm across) it may be possible to fit it into quite a big shutter by sinking each cell well back so that it only just clears the shutter blades and diaphragm ring. Sorting out the diaphragm is another matter: note the non-linear aperture scale from f/16 to f/64.

putting lenses in front of (or behind) shutters

This can work perfectly well as long as the lens does not cover too wide an angle, in which case mechanical vignetting by the shutter is the problem. Even this may not be a problem of you can get the front or back surface of the lens close enough to the shutter, and if the shutter is big enough. Shutter efficiency is reduced, it is true, but this is unlikely to be a problem at the longer speeds that are usual with old LF lenses, and besides, it is easy to compensate for. Our 14 inch (356mm) Taylor Hobson Cooke Apotal has been used in front of the enormous Compound illustrated since we acquired it decades ago, and the standard shutter on our 21 inch (533mm) Ross f/7.7 is a Thornton-Pickard, again as illustrated. But TPs are another story...

 

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© 2006 Roger W. Hicks