Aunt Em

AUNT EM'S PROBLEM PAGE

Aunt Em is here to try to provide answers to the questions that experts generally take for granted, leaving the novice floundering because basic building blocks of understanding are missing.

Aunt Em is always glad to be corrected or to get extra info from smart Alecs.

Q. As you dissected a André Debrie 16mm-projector I hope you can answer a question which has kept me busy since someone told me: "I don't know if it is a good idea that you bought that old projector from a woman who had never used it. Oil has certainly clotted in the thin pipes of the oiling system." And indeed it seems it has. How can I change the oil? In spite of the fact this pre-war model of a projector looks awfully solid I am a little afraid to break something crucial. I hope you can to help me.

A. Please bear in mind that my only experience is with the grey D16 model.
I would be very surprised to find that oil has solidified as you suggest. Do you have any particular evidence for this?
What I did find was that thin oil will not work in this machine. The oil is circulated by a fairly basic mechanical pump and it needs quite thick oil - car engine oil sort of thing - to function. I assume you know about the oil flow adjuster at the top.
You will have seen the drain plug at the bottom of the lower oil reservoir. You can drain the oil quite simply through here. If there is a serious problem of clogging, you may be able to use a specialist car product designed to flush an engine. This may be preferable to dismantling, but I wouldn't worry too much about taking the machine to bits - it was
specifically designed on a modular basis so complete assemblies could be easily replaced. You could try mixing thick oil with something like WD40 to flush the system through, but if it's too thin, it won't go round. I think the whole front section will come off if you remove the screws on the perimeter of the round section - just take the usual care not to lose
anything. You will need to do this if you decide to open up the lower oil reservoir - one of the two screws holding it on is only accessible if you remove the front section. Please think carefully before doing this - there are oil seals top and bottom of the reservoir which you would have to make watertight (and oil-tight) again. Also, if you are afraid of breaking
anything, the glass of the reservoir is one of the most breakable parts. Best left alone. You can remove the oil tube running from top to bottom quite simply just by undoing the two nuts - these again form oil-tight joints, but should I think go back OK as I think they rely on compression rather than seals. I think the first thing to do is drain whatever oil is in there and try some thick oil. However, if it is really true that oil was never added, there may be mechanical damage. This machine is designed to run with a constant flow of oil and if this wasn't done, either from lack of oil or failure to adjust to
keep the flow going, it could ultimately seize up.

Q. A Specto question. Other than a mistimed shutter can you think of what may cause a ghosting to appear on mainly intertitles. Is this something that could be caused by the claw?

A. I suspect ghosting is there on pix too, it's just more noticeable on titles. I can't think of a cause other than shutter/claw timing, tho' I am not sure of how this is adjusted on a Specto - must look sometime!

Part of the problem may be the old story of how to get enough light to the screen. Specto used the "grasshopper" type claw mech, where the claw makes two strokes per frame, but only engages the film on one. This means a faster claw action and so a faster pulldown and so more light thru to screen.

This however is achieved by reducing the size of the shutter blades, and sometimes they went a bit too far. Somewhere buried in the Premier Pathescope 28mm instructions (see website) is a reference that suggests the intermittent (already slower than a claw, anyway) actually starts to move before the shutter fully obscures the image and vice versa after, and even claims this as a good thing!

I suspect, too, that ghosting , as with flicker, becomes more noticeable as you increase the light output and change to the whiter light of tungsten halogen.

All of that said, you should not get ghosting with a Specto and it seems to need some adjustment. If all else fails, you could even try making the shutter blades fractionally bigger.

Another thought that has just come to me is whether, with non-optical framing, prints that require maximum adjustment of the framing one way or the other might actually throw the claw/shutter alignment fractionally out of whack. This sort of thing makes my brain hurt; it will take me some time to think this one thru and figure it out.

Q. I recently acquired a very nice Heurtier HSM (or is it a Panoralux?) multi gauge projector. The machine is in exceptionally good condition and appears to have had little use, however it has been unused for many years. The result was the gear box speed changeover was seized in the 24FPS position. After clearing out the old gearbox grease and generous use of Plus Gas on the seized components I eventually got the seized components freed off and the speed changeover now works as it should.

I am puzzled by the following; set up for 16mm, the machine can be turned over with the inching knob fairly easily; set up for 9.5mm and 8mm the machine becomes quite tight to turn over although it starts and runs OK with the motor. Is this normal?

The instruction book indicates a lever on the sound optics to adjust for the narrower track on 9.5mm. This lever is not fitted to this machine. (I think I could see a similar machine on one of your web photographs i.e. without the changeover lever) Any comments on this?

Do you have a circuit diagram of the amplifier and exciter lamp supply?

A. As far as I can make out, the only difference in the Panoralux is that it has a Debrie-size lens mount, not the smaller type as in the silent Heurtier and my very dirty optical-only machine. Bit concerned about the difference on inching between 16mm and the other two. Could be that it has mainly been used for 16, but even so - I assume you have oiled the claw? I have a very little used machine that is very stiff altogether. But if it runs without weird noises.......

All three of my machines have the 9.5/16 adjuster - it can be seen very clearly on my website in the picture of the stand-alone Panoralux, back of sound tube near exciter cover. I assume you have the same daft exciter lamp (tho' my double-band machine had been converted even before I got it). I have found a spare on French ebay, but they are like hen's teeth. No diagrams, I'm afraid - I wonder if anyone has them?

Q. My machine appears to have the smaller lens mount so must be the HSM model. On your converted exciter machine has a "Elf" type lamp been used for the job? I attach a couple of pictures of my machine which show the absence of the scanning slit changeover lever. Any ideas why this should be omitted? May have to take the optics off and narrow the slit to 9.5mm size as this is what I will be mainly using the projector for.

A. I can think of only one answer, as it's obviously meant to be that way. I have heard it said that in the old days, cinema projectionists would narrow the sound slit so that the beam only picked up the least worn part of the track. I suspect Heurtier may have found that, if the set-up had enough power to produce a good volume from a 9.5 track, why bother with expanding it for 16? The corollary, of course, is that it was mere penny-pinching and they left it 16mm size, not caring what happened to 9.5. I assume since you are considering the extreme step of dismantling, you have already tried the 9.5 sound and found a problem, which would tend to favour the less favourable of these two possibilities. The lamp conversion on my double band used a slightly smaller bulb, 24v 10w, small bayonet with 2 pins, with 2412 U and Bay 15 on the box. I've not come across them, but I've got a small stock so haven't looked. It might not work for you anyway; at the same time as the lamp, the photocell was changed, too, to a solar cell/diode, which might give higher (or lower) gain than the original.

Did you note the bit in Multi-Gauge about using a reversing prism and running the 9.5 film the wrong way round? I find it very difficult to get a tenable loop at all with that twist, and it must put a considerable strain on the film. A square piece of wood the size of the 9.5 sound aperture placed in it and twisted turned the mask thru 180 degrees for this.

Q. I have finally got all the facilities on the Heurtier running OK with the exception of the sound on 9.5mm optical. I removed the sound optical system with a view to masking it down to 9.5mm width but found it to be a sealed unit and I was reluctant to try to open it up. (The masking down has to be made close to the mechanical slit inside the unit) so I refitted it to the projector unaltered. The problem is, with the 16mm slit width the 9.5mm track is scanned plus the area either side of the track resulting in heavy background noise.

A. Are you sure the masking needs to be done inside? I know Tony Reypert used external masking on at least some of his Buckingham 9.5 conversions, to deal with exactly the same problem. Worth a try, I would say. I can't see any reason why it wouldn't be at least as good, at the bottom at least, as inside.

One of my Rurals has got a thing at the top of the sound lens tube that you rotate. It has eccentric masking so that more or less of the sound tube is covered. I did think of doing this sort of thing myself for something, some time ago, although at the bottom rather than the top, but I have forgotten what!

As for it being a sealed unit, if by that you mean that the screws have some sort of seal over their heads, I wouldn't let it worry you. You can't do much to a Heurtier without breaking some of these, and it's not as tho' you might need to make a claim under warranty and need to prove you haven't done unauthorised fiddling.

Q. I have a question about the Pathé Baby motor. I recently acquired one from Buckingham films, and it works fine on the 115 v 60Hz here in the USA. But I am somewhat concerned about it's safety as the internal wiring looks pretty bad and the connections to the mains terminals look pretty dangerous. I am considering taking it apart and attempting a rewiring job. Would you advise this or not, and how difficult a job is it? Any pitfalls to watch out for, or any recommendations?

A. First off, make sure you have a really good earth connection, and use what we call an RCD (Residual Current Detector, I think), which trips out if something's wrong.

Second , be careful, and remember to be careful always, which is the hard bit. Try to get the mindset that NEVER takes a chance.

These two should keep you pretty safe. As to the wiring, the bit that matters most is where the wires disappear inside the motor casing. If these break, and being old and brittle they might, you have a problem. Leave them alone as far as possible, and don't let them get bent if at all possible. If you have this problem, we need a more detailed look, ( it's fix-able often, but tricksy) but I'll assume for now you don't.

Anything downstream of the above you can replace with impunity, but watch out for the resistance for the speed control. These wires, too, can be very fragile, and altho' you may be able to replace with a modern device (eg a light dimmer), it's a lot of hassle and a shame to have to do it. The contact on some can get stuck to the wires and break them; the stuff the wires are bedded in tends to disintegrate and maybe let the wires move - the first step towards failure - and you may get corrosion on the contact, causing extra friction and poor conductivity.

Things I find especially useful in this context are heat-shrink plastic sleeving, which can add strength and support as well as insulating, tho' it's a bit inflexible, and some insulating rubber solution I got from a supplier of car restoration stuff. You can get it into all sorts of corners where you can't wrap tape, which doesn't really last anyway. This could be useful where the wires go into the motor casing. It is also possible to get the resin-impregnated sleeving used in the old days, if you want to do a pukka restoration.

I have a number of old Pathé Vox machines, which use a 3-pin input plug, two of which are the same, just connected together. Isn't the Baby motor similar? I have used one of the duplicates to provide an earth, but I have to put a label on the projectors I've converted as, if they were connected to an unmodified input, you'd get a live casing, not generally considered good practice (!)

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Q. I am trying to fit a 12v 100w dichroic mirror lamp to a Bolex (maybe 1 24v 200w would be better). I have made an adjustable bracket using a lampholder from an Elf 16mm machine. How do I position the lamp to get the best light? What are the criteria?

A. There is only one criterion - what it looks like on the screen. There are specific focal distances for such lamps (some are quoted in Lamp Data), but these are more use to manufacturers of projectors than to the amateur. The distance is apparently measured from the back of the mirror rather than from the filament for one thing, which makes it more difficult, but anyway, it does not address the issues of lateral and vertical location, which are just as important. There are variations in focal length, there are primary and secondary foci, there are differences relating to the size of the gate aperture you are trying to illuminate (unhelpful if you are attempting to deal with a multi-gauge machine, especially if 8mm is involved. The tri-gauge Bolex G3 had a special lens to deal with the offset of the 8mm aperture, but the lighting has obviously to be a compromise when there is a 3- or 4-fold difference in aperture).

So at the end of the day there is no practical alternative to good old trial and error. The way to do this while keeping both your fingers and your sight is to feed a reduced voltage thru to the lamp - 6v should be ample for a 12v lamp, and you could probably manage with it for the 24v lamp too. (Don't go thinking "Ah yes, halve the voltage", because you will literally get your fingers burned if you try that with the higher voltage lamp.) This should give you a level of light sufficient to gauge the best lamp position, using a small screen a few feet from the lens, with a reduced level of heat that should help with handling. It's still a fiddly job, but is much eased by an adjustable holder such as you have - once you get the position approximately right, you can fine tune. You may have noticed that with some projectors the lamp glows when the projector is on. This is supposed to warm it, prevent thermal shock and prolong lamp life as compared with going from cold to full power. This question of lamp life seems to have exercised amateurs quite a bit in days gone by, judging by old copies of Home Movies and Home Talkies, for example. This uses just a couple of volts at most; what you need is just a brighter version.

Don't expect to get a perfectly even illumination - you need to go for the best compromise between evenness and brightness. Once you apply full power, and with a film in the gate, it will be impossible to detect any unevenness. One final point - disengaging the still frame mech to avoid accidental operation might be a good idea.

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Q. Do any operating instructions exist for the Pathé KOK 28mm projector? if not, can you tell me, what the small knurled disc on the main body just in front of the gate, with what looks like a ball bearing in the centre is for? I assume the hole (with cover plate) just under the lens is a oil hole?

A. Mais naturellement il y a un manuel! Vous le trouverez sous 28mm, nommé Instructions. Malheureusement, le manuel est en Français, ce qui pourrait poser quelques problèmes pour ceux d'entre nous qui ne peuvent pas hacker le Froggo. En plus, le manuel ne traite pas des trous dans votre question, mais il serait étonnant si tous les deux ne soient pas pour l'huile.

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Q. Which way round does the film go thru the projector? Which way does emulsion face? Which side of the spool does the film feed from?

A. This is all the fault of Pathé, who made their silent films, up to the time sound was introduced, unspool from the back of the reel (ie nearest the projector). No other film does this as far as I know. It may be because of the gauge's origins in 30ft notched cassettes. The emulsion had to be on the inside to protect from rubbing on the metal cassette, and the design required a feed from what would become the back of the reel.

The important thing is not the position of the emulsion (unless perhaps you are loading film chargers?) but whether the film appears OK on the screen, with titles the right way round, right side up, from the start rather then the end and preferably with the sound track on the correct side. If all of these are right, who cares about the emulsion? It does matter, of course, because projectors are designed to minimise any rubbing. The emulsion is on the inside of sprockets, away from retaining rollers, and rollers that take the film round corners do it with the emulsion on the outside wherever possible. With 9.5, there is the unique factor of potential claw scratching in the picture area. It makes sense, therefore, for the emulsion to face away from the claw. We have all seen the damage a Baby claw can do. It may well have been this that ultimately made Pathé change (the Vox, H, 200B, Lux et al all have the claw in front of the film). I seem to recall some reference in the amateur cine press or maybe Pathescope Monthly on the reasons for the decision - anyone got chapter and verse?

So, basically, except for most 9.5 silent, feed from the front of the spool (or underside as I sometimes think of it), and never mind the emulsion so long as the film is right on the screen. Sometimes this means a twist in the take-up belt to get it to rotate the right way. It's not the end of the world if a film takes up the "wrong" way, tho' it can mean it winds floopy and could mean problems if the film is near the normal maximum capacity of the take-up spool.

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Q. What is the difference between Regular 8, Super 8 etc?

A. Regular 8, Normal 8 and Standard 8 are all terms for the first 8mm gauge. This was created by doubling the number of perforations in 16mm film, and having four images in the space previously occupied by one 16mm image. The film was produced 16mm wide, and run through the camera twice, (hence "double-run" 8mm) then split after developing. The advantage was much greater economy both in film used and in developing. Kodak introduced the gauge in America in 1932, and shortly thereafter it came to Europe. Eventually, magnetic sound was added and experiments were made with optical sound; one or two projectors were made able to run this, but remained curiosities as there were no films to buy.

This was because Kodak introduced Super 8. This was widely suspected of being a marketing ploy to get enthusiasts to buy all their equipment all over again. However, whatever the truth in that suspicion, there were sound technical reasons for the change. The Standard 8mm image was tiny and, although capable of producing excellent results, was a highly inefficient use of the film area because of the (relatively) giant 16mm sprocket holes. Adding sound just made things worse - tiny tracks straining to produce acceptable results, or yet further loss of image area. Super 8 had very small sprocket holes (too small some said, concerned about how long films would last) and an image that was both wider and taller, even with a sound track (magnetic for the most part, but optical particularly for use in aircraft entertainment systems). A magnetic sound track adds thickness to the film on one side, so a "balance" track, squeezed between the sprockets and the edge of the film, was added, which was exploited to give stereo sound.

At about the same time, Fuji introduced Single 8. In terms of format (film size etc.), this was identical to Super 8. The difference lay in the film cartridge, which was much more on the lines of Pathé's 9.5mm chargers than the squarer Super 8 cartridge, with feed and take-up one above the other rather than side by side as in the Kodak cartridges. The other difference was that Fuji used polyester-based film, stronger than acetate so it could be made thinner. This helped with the amount of film that could be got into their cartridge (9.5 never managed even 30ft) to match Kodak's 50ft cartridge. The only disadvantage with polyester (if you think it is a disadvantage), is that it can't be spliced with normal cement and so for practical purposes could only be spliced with tape. Polyester commercial prints can be found, looking suspiciously short on the reel for their claimed length.

The row about the introduction of Super 8 to confuse the existing multi-gauge scene was huge and rumbled on for years. Some of the sting was removed by the introduction of Dual-Gauge projectors for both Standard 8 and Super 8. Some machines even claimed to be triple gauge, citing Single 8 which was, of course identical to Super 8 (barring some projector problems arising from the thinner film base.

One problem that could not be, or at least was not, overcome, was projectors able to show Super 8 as well as 9.5 or 16. Standard 8 had a 16mm background and, by coincidence, the pitch of 9.5 and 16 was almost exactly the same. This meant (genuinely) tri-gauge projectors could be made (see Multi-Gauge).

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Q. What are notched films?

A. When Pathé first introduced 9.5mm, the maximum length of film in a film charger and in a cassette for the projector was 10 metres or 30ft. This presumably reflected the rather limited thinking about what was a very new venture. Later, 60ft cassettes were added, then Super Attachments taking up to 300ft. In order to get the maximum run time out of such a short length, Pathé decided to use still frames for titles, and often for the start of scenes or for static shots. The Baby projector had an ingenious device for allowing this. A notch in the film allowed a small cam to move, setting in train the withdrawal of the claw and a mechanism that automatically re-engaged the claw after a fixed number of turns of the crank handle. (The earliest Babies had a very long "dwell" time; this was later reduced as being too boring). This enabled the short cassettes to last for as much as three or four minutes, as opposed to little more than a minute if run without pause. This was all part of a total design concept; with all this stopping and starting, it was too complicated to have sprockets, and of course a low power lamp was essential to avoid frying the film. This in turn meant relatively low illumination levels, positively dark by modern standards but apparently more acceptable in those days of innocence.

The notches in the film obviously showed on the screen, so the film actually stopped a frame later to give a proper picture. An important additional feature was the provision of a slot near the end of the film, replacing the perforations. The claw could not operate, so the film stopped before it was shredded or ripped out of the cassette; the end of films was securely fixed to the tiny core in the cassette. An interesting sidelight is that the front ends of films were specially heat-treated to impart a curl to ensure smooth feed through onto the take-up in the base of the machine. Pathé actually patented this idea. Many printed films also had a very shallow but very sharp oblong notch in the opposite side to the main notch; I've never known why. (I asked an expert, the legendary Patrick Moules. He said that when triple prints were notched, before being slit, the notch was either slightly over-size or out of position, so that the outer part of the notch cut into the adjacent strip. This only happened, of course, with two of the three strips.) Notching devices were sold so that 9.5 film users could put the correct notches and slots in their own films. One other thing; many notched prints came from a period when the image quality was superb, which is why they are so prized by collectors.

The problem was that, as time went by, demand grew for higher levels of illumination. This meant more powerful lamps, that emitted more heat. Huge numbers of notched films now bear witness to the disastrous consequences; ignoring all admonitions to use the correct, low power lamp for notched films, users blithely disregarded the consequences, used the higher -power lamps and fried the titles. These then shrank and buckled or even burned right thru; splicing the damage out was a very limited option since there were so few frames of title to start with. Opening titles seem to suffer the worst and are often completely absent. At one time, Pathé sold sets of running titles that users could splice into their boughten films, either to repair damage or for use on high-power projectors or ones that couldn't do notches anyway. Given Pathé's penchant for using lots of titles to disguise cuts made in editing, this can't have been very popular.

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Q. Why do low voltage lamps give more light than mains lamps?

Getting a bit technical here. As I understand it, lower voltage lamps can have their filaments more closely spaced, giving more intense light in a smaller area, highly suitable for narrow-gauge films (is it something to do with how far filaments must be apart at different voltages to prevent short-circuiting or arcing?). Another factor at play is that, for sound machines like the Vox, Debrie and GB L516 that used the lamp to read the sound-track, rather than a separate exciter lamp (which tend to be low volts/high amps - see the end of the table in lampdata.wdb), the lower the voltage the better. Lower voltage means less hum from the AC supply, I am told. Quite how this applies to 110 volt machines like the Debrie and GB L516 I don't know; maybe they deal with the problem in the amplifier.

Quartz Halogen, Quartz Iodine (QI), Tungsten Halogen etc. are all terms for a technology quite different from the straightforward incandescent lamp. They can be smaller, with smaller filaments, yet give brighter and whiter light, especially when combined with a built-in dichroic mirror, which removes the need for a condenser lens - a significant advantage for old projector nerds trying to uprate old projectors. So, for instance, the standard 24v 250 watt lamp with integral dichroic mirror gives a better light than a 1000 watt or even a 1200 watt incandescent. QI lamps need to reach a certain temperature to operate properly; I am told they also dislike direct cooling and can go black if direct cooling is applied, but they produce much less heat than the equivalent incandescent. They quite rapidly became the standard for narrow-gauge use, relegating the incandescent lamp to history. The peanut-type QI lamps can pretty much directly replace old lamps, tho' some experimentation with exact mounting position might help. Basically, I feel that if the filament is in the right place, then fair dinkum. Dichrioc mirror lamps have a specific focal distance; examples are in the lamp table referred to above. I think there may be more to be said on this subject; input would be welcome.

Then, of course, there are even higher power lamps. There was a version of the B&H 620/630 series with a carbon arc, the B&H 609. I've never felt brave enough to consider carbon arcs; complicated. Then there was the Marc lamp, which B&H in particular tended to use. They were some form of discharge lamp, and took a while to reach full operating output and colour temperature. They also needed complicated boxes of electronics, and used high-voltage circuitry. This last bit is also true of Xenon lamps, and some early machines had large separate boxes of stuff. Then came switched mode power supplies (I can say it but I don't understand it) which allowed much smaller boxes of gubbins and could therefore be fitted in the projector. Most Xenon machines were 16mm pedestal models, which had lots of room for boxes of electronics, but there were some semi-portables like the Elf 2000 series. B&H also did them, but I've never seen one. I'm accused of being a light freak because I have Xenon's wherever I can 8, 16 and 35.

Beyond even Xenon in terms of potential for narrow-gauge users is the sort of lamp being fitted to digital video projectors. Bill Parsons converted a GS 1200 to one of these lamps, and a direct comparison was arranged at a film convention; no question, the new lamp was brighter than the GS 1200 Xenon.

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Q. Projector lenses are quoted for example as having a 1 1/2 inch focal length and f/1.9 aperture, but what does this mean? How does it affect the projected image?

A. In short, the focal length is about how big your projected picture will appear on the screen, and the aperture is a measure of how much of the light coming from the film is actually allowed through by the lens. It is, of course, much more complicated.

Most projector instruction books come with a chart that shows the size of picture you will get at various distances (the "throw") with various lenses. It should be obvious that what you get depends on what you start with - 8mm is going to give a much smaller picture than 16mm for a given focal length and throw. This is why lenses for 8mm machines have shorter focal lengths than 9.5 or 16mm machines. 16mm projector manufacturers were all convinced that their machines would only ever be used in modest-size halls or palatial mansions, as they supplied 50mm (2 inch) lenses as standard. These are about no bloody use at all in the average house as they give a tiny picture unless you knock holes in a few walls. As a result, 50mm lenses you can’t give away, and shorter lenses – 35mm or 25mm – attract a substantial premium. Mind you, I look sometimes at the huge cost of new lenses and this puts things in perspective.

Because in order to have different picture sizes, or for different venues, you needed several lenses, zoom lenses were introduced for those who couldn’t even change a lens. This was one area where Super 8 scored over everyone else – the machines came with a zoom lens of a focal range appropriate for home use. Theses are often re-deployed to 9.5 in particular. Certainly, it was once true that a good prime lens would give a sharper, brighter image than a zoom, because there were by definition fewer elements stealing light or fuzzing the image. Given the advances in optics, I doubt that this is any longer true. Incidentally, it does seem to be the case that the shorter the throw of a lens, the more critical is focussing – the tiniest of movements can destroy focus, where longer lenses have a somewhat longer travel within which focus is reasonable. The problem is not so much that it’s tough to focus, as the fact that small changes due to heat in the projector or lens can throw focus out. As with any lens, how sharp the image is comes down to lens quality. Larry Pearce once cannibalised very short throw lenses (20mm?) from Technicolor continuous cassette loop projectors and put them in mounts to suit certain projectors, eg the Vox. The quality of these was good and they give good results despite the very short focal length.

The other factor that comes into play is lens coating, or blooming. This helps to reduce light scatter and so improve both light transmission and sharpness. Since older projectors tended to have un-bloomed lenses, this affects image quality. Another problem with older lenses, or those exposed to damp or whatever, is fungus. This manifests as a spidery network of fine lines spreading across the lens. It then needs specialist attention – removing the elements without damage, cleaning and re-assembly and re-cementing. (Terry Vacani tells me he does this – details on request).

To come back to aperture size, the bigger the number, the less light a lens will pass. Whether variations are always discernible to the average eye is a moot point, but at one time there was a bit of a competition to see who could produce the fastest (most light thru) lens. I think Elmo pretty much won with a 1.0 zoom lens on the GS 1200. As a rule of thumb, anything 2.0 or less is fine, but bear in mind that the longer the throw, the higher the f number, so it is normal for a long-throw lens to have a higher number.

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Q. There is a conversion of the Eiki/Elf 16mm projector available for 9.5 silent called the "CLASSIC" it has fixed speeds of 18 f.p.s. and 24 f.p.s. I thought that silent film ran at 16 f.p.s., although I understand this could vary, hence the variable speed controls fitted to early machines. So why does the "CLASSIC" have only a fixed speed of 18 f.p.s.?

A. Most silent projectors have a speed control, usually a resistance or a friction brake. This is partly because the type of motor used runs faster as it warms up, and anyway each motor and projector would have slightly different characteristics, so the ability to control the speed was useful. The effect of load on motor speed is most readily seen in projectors with a clutch; run a film at normal speed, then de-clutch, and the motor races away. You get this with the Bolex PA/DA when it stops at a notched title. It was also helpful when showing all those mute prints of sound films to be able to speed things up a bit, so people didn’t all look like they were in a slow-motion action sequence from films such as The Matrix. (How on earth did that silly idea catch on? And the idea that anyone can dodge bullets, or that villains are hopelessly bad at aiming their weapons at where the hero will be in a few instants’ time?)

This is no use when it comes to sound, which needs a constant speed, the smoother the better. You can of course use a governor to control the speed, but the motor needs to be powerful enough to run at the much higher speed of 24fps right from a cold start. The classic failure in this particular area was the Son (ugh). In order to get the motor to run at 24fps from cold, it was wound for 160 volts and fed with 240 volts. This is not good for a motor. Also, as the motor warmed up (which it presumably did pretty quick being over-volted), it went faster, so the governor had to work harder to keep the speed down, leading to interference with TV and radio and breakdown of the governor contacts. To minimise the damage, you needed to ease the resistance speed control back as the machine warmed up, but not too far, or the sound went slow. Sons (ugh) therefore spent more time back with Pathescope being repaired than with their owners. Because of their unstable speed, sound add-on units such as the ACE and the Aurator for silent machines were poor for sound.

Those who understand governors can skip the next couple of paragraphs, but I thought someone is bound to ask so I’d better explain a bit. Any governor controls speed by a feedback system – as the machine reaches the pre-set speed, the power is reduced to slow it down. In a projector, this usually takes the form of centrifugal "switches" on the rear of the motor. These are so arranged that as the motor speed rises, a small spring-loaded metal strip, fixed at only one end, is flung outwards by centrifugal force, breaking its connection with a fixed contact. The power supply for the motor travels through the circuit made when these two contacts are touching, so when the connection is broken, the power is cut, the motor slows down, the contacts re-connect, speed goes up, connection is broken……..…and so on, only very quick. On the more sophisticated machines, a screw adjuster is provided to help set the precise speed (usually two speeds, of course). On cruder machines including, regrettably, the Pax, you have to bend the afore-mentioned spring-loaded metal strip as best you can to set the speed entirely by trial and error. Mind you don’t break them!

However, there is then the problem of actually establishing connections with the end of a motor whizzing around at high speed. This is usually done by motor-type carbon brushes running on brass strips around the surface of the end of the motor, on which the contacts we have been talking about are also mounted. Between them, the contacts and the brushes create sparks as contacts are made and broken at high speed, bringing a need for suppressors to prevent interference. You also need a resistance in the silent-speed circuit to take some of the load, so that the governor is not overworked as in the Son (ugh). Modern machines do it all differently and electronically in a way which I do not understand, so don’t ask.

Anyway, to return to our moutons. The point of the foregoing is that sound projectors, which all modern machines are, have essentially fixed speeds that cannot be varied as on old silent machines. So the Classic, which is a conversion of a modern sound machine, has fixed speeds. The reason the silent speed is 18fps rather than 16 is, as I recall, that Kodak introduced this when they introduced Super 8, with the idea that the slightly higher speed would give better results for people adding sound to their silent films. I assume the single-system sound cameras introduced rather later were also 18 fps, tho I‘m not certain (I don’t really do cameras). For some reason I wot not of, this speed change spread to 16mm. Incidentally, since the speed change on the Elf from which the Classic derives is by swapping a belt on a two-part pulley, one could if desired have a 16fps pulley. I understand Tony Reypert has done one or two like this (at extra cost, of course).

All this speed business is a bit irrelevant unless you are running your own silent films on Standard 8 or 16mm from long ago which were actually shot at 16fps. In the commercial cinema world, there appears to have been no such thing as a truly standardised silent speed. In the early days, it depended on the cranking speed of manually-operated cameras. Later, silent film speeds tended to increase, and by the end of the silent era speeds as high as 22fps were not uncommon. Before sound and the need for a fixed speed, it was common practice for cinemas to run films at a speed that suited the desired length of the programme, eg to increase the number of showings to increase takings. The other factor is our own perceptions. To us, films projected at 16fps can seem slow, with interminable titles, used as we are to a much faster cinematographic pace. 18fps partially addresses this without doing too much violence to the projected image. (You will recall the days when silent films on TV were run at 25fps to suit TV technology, giving speeded-up, jerky motion - OK maybe for the Keystone Cops, but horrid for, eg, Battleship Potemkin. And then they started doing stretch printing, repeating some frames to get lower apparent speed, but still producing an unnatural-looking motion). At the end of the day, it is down to individual preferences and individual films as to what looks right, but you do have to work within the technological constraints that conversion entails.

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Q. Am I right in thinking that a sound projector, designed for the American 110 volts supply,
used on the UK mains via a step-down transformer, will run slow due to the difference in mains frequency?

A. Yes. Unless you change the pulley (see above

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Q. If my main interest was collecting silent 9.5 films, what projector would
you recommend? I would prefer to use a vintage machine rather than a modern conversion.

A. Definitely a "how long is a piece of string" question. We need to define our terms a bit to start with. When you say 9.5mm silent, I think we have to assume that that includes notched films. This is because some films are only available notched, but also because it is the notched prints that so often have that wonderful sharpness and clarity. And when you say conversion, I will assume you don’t rule out things like lamp conversions but mean simply a projector designed ab initio to run 9.5. We will also assume you are not interested in "toy" projectors, in which class I place things like the Ace, Kid and Imp as well as the more obvious Bingoscope, Hunter or whatever.

So we are left with three basic options; the Baby, the Lux and the Bolex PA/DA. I think the Baby, fun tho’ it is, is too limited in lamp and lens terms, quite apart from being "stretched" from 30ft to 300ft rather than designed for it. At the other end, the Bolex, while capable of excellent light output, has the fatal flaw that it must be restarted after each notch, of which there may be several per title. This is just too distracting even for you, let alone an audience. So it comes down to the Lux but, of course, great care in selection is needed because of the Mazac disintegration that affects motor and gate. You really need to find the later YC model, which has a steel gate, because although motors can be replaced, it’s a lot more difficult to replace the gate. With a modern lamp and a better lens – say an old-style B&H, which can be fitted to a bored-out lens sleeve – and a modest screen size, the Lux will give good results. You could of course go mad and splash out on a Coq d’Or, if you can find one. Among other features, it has the shutter between the lamp and the film, an immediate and substantial reduction in the amount of heat getting to the film without affecting the light on the screen. But don’t go mad – he who uses a too-powerful lamp and burns the titles of a notched film shall be cast into outer darkness and allowed to have only Std 8 films until his crimes are purged. But unless you are a keen and dedicated nerd, you run the risk of serious film damage because the Lux has no sprockets and, basically, that is just asking for trouble.

What the Lux will not help you with is the multi-reel silents like Metrollopis (with running titles), or the White Hell of Pitz Palu. You can do it on a Lux, but it’s a lot of changes. So you may want a second projector for such films. A Bolex with arms extended for 900/1000ft spools would cover both, but projectors are still so cheap, why not have two? As my partner says, a boy who knows how many projectors he has hasn’t got enough projectors. Here your scope is much wider – as well as basically 9.5 silent machines like the 200B, Specto, Eumig P3, Gem et al, you can branch out into multi-gauge with the Heurtier Supertri or the Bolex G3, and of course all the sound projectors are there for you as well, tho’ you usually get a fixed silent speed with them. There are more esoteric machines like the Europ, but these are rare. My own choice is the Specto – you can have a 9.5/16 one if you feel like branching out - or maybe the Heurtier. But if you are like me, you will do your best to have all of them. My partner is quite right - a young friend on a visit once counted my projectors and found 48. I have to confess I panicked - 48 is such a pathetic number - and rushed off and bought half a dozen more (only then did I find two projectors missed in the count) and have not looked back since.

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