Kinoton FP25D threading question

[Leo Enticknap]

And gate tension is more of a live issue in arthouses than in first run theaters during the final decade of film as a mainstream release medium. In the latter, 99.9% of the stock that passed through the projector would have been Eastman 2383. I never noticed any difference in thickness between batches - at least, not enough to require gate tension adjustments in the projector.

In an arthouse/rep/cinematheque type place, however, you could be handling anything from tinted and toned 1920s nitrate at one end of the spectrum (so thick it's barely flexible, in extreme cases) to Eastman 2302 (so thin it's like handling non-adhesive Scotch tape) at the other. At the Egyptian I would check the gate tension after every changeover. Usually I barely had to touch it after the first reel of each feature print was running, but significant adjustments were needed occasionally.

[Simon Wyss]

The Philips FP series have a mistake in the design of the gate. The rigid side is formed concave and the mobile side is convex. Each time the intermittent sprocket is pulling the film wants to lift the pressure insert, the more so pressure is increased. That is why you never get below a certain pressure force. A well maintained and adjusted FP has the index a little towards the minus symbol of the pressure indicator but mostly around the middle. Depends also on the state of the built-in spring.

Next lateral film guidance is not according to the idea within the standards which goes with a reference edge and a guide edge. You have four ceramic spring loaded discs that clamp the film from both sides. The springs are stronger on one side, if everything is installed correctly. A little awkward

Synchronism is a floating thing with flywheels. You have a flywheel on the sound drum shaft. The elastic film sets spontaneously to a picture-sound distance you cannot influence anymore once the projector operates. What you can and should do is to 1) thread the print with respect to the actual sound advance you read from the start leader and 2) with respect to the viewing distance the majority of spectators will have on the show. Let me explain.

1) On an original start leader you will find a START frame and a 1kHz sine-wave beep on the soundtrack of one frame length. With a perfect print they are separated 21 frames or 84 hole pairs. Count that and note for each roll, it may be 85 or 86 or 83. Inch the projector mechanism to the middle of the projection part of a cycle, i. e. the shutter covering the aperture. With some projectors the shutter is visible through a window or an opening somewhere and a mark on it can be seen. Now put the START frame in front of the aperture and close the gate. Finish lace-up from reel to reel while checking that the diamond sign line falls under the light beam of the sound reader when you pull out the lower loop.

2) When the viewing distance is not the average one laid down in the synch concept, namely 45 feet (the half of a 90-feet auditorium under a 100-ft. projection distance), you make the lower loop longer in order to delay sound a little. You can do that only in steps of perforation hole pairs. There are practically no projectors known that would allow stepless adjustment. At 24 frames per second speed a perforation hole distance or pitch length corresponds to 1/96 second. The speed of sound is 1126 ft./s at 68 F, so each quarter film step makes for a little less than 12 ft. The difference of one frame length between the sound pulldown on the film and the reproduction offset in the projector, 20 frames, balances the difference between the speed of light and the speed of sound. Of course there is some elasticity of perception but we projectionists ought to know the story.

The sound reader of an FP can hardly be shifted but models differ. In the early days when engineers took care of film sound the readers could be pushed up to and pulled away from the projector enough so that dead-on synchronism was achievable. It’s also been called pistol advance because of the importance of a pistol-shot coming at the right time. All in all the size of the lower loop is given.

Your upper loop is a little too long. Try to make the film kind of drop in between the rails and the pressure plate. At its best the film can run on an FP with just a fluttering noise of the loops. For this the geometry of rails and plate needs to be a match.

[Steve Pike]

Hey all
fhabks for all the comments. Interestingly I've just tried my first full feature film (Madagascar, 2005) and I had to increase the gate tension to almost on full plus as the film was jumping all over the place on screen and pushing the gate out on the projector. Yet for my other set of films (old ads and trailers) it was ok with being in the middle setting.

I don't think the print of Madagascar has ever been shown, or if it has it was using changeover as all the leaders were still complete with no splices from platters or towers.

I've adjusted the loops size through trial and error and I seemed to have found the "sweet spot" for operating now.

[Randy Stankey]

The Philips FP series have a mistake in the design of the gate...

Correct me if I am wrong but this is the way I understand...

The focal plane of a lens isn't necessarily a "plane" but more like a "zone" that is shaped like a shallow parabola with its focus at the central nodal point of the lens system. Therefore, in order to keep the film image in the focal zone, the film should follow a curved path to match the shape of that parabola, at least for the frame of film being projected at a given point of time.

If that is true, the stationary part of the film trap should curve so that it bulges toward the lamp, having its focus pointing toward the lens. The moveable part of the trap would have to match the curve of its mate, also bulging backward, having its focus toward the lens.

The intermittent sprocket is positioned below and slightly forward (toward the lens) so that its clockwise rotation pulls the film down and forward, out of the curved trap.

I understand that many projectors are arranged this way but not all. There can be variations in the way projectors are designed. That's competition. Right?

How is the Philips FP different? I guess I don't understand because I don't see how, in a projector arranged as above, the rotating intermittent sprocket could pull on the film in a way as to increase film tension.

It seems to me that a well designed projector would be engineered such that it places the least possible amount of tension on the film which still produces a steady picture.

What don't I understand?

[Simon Wyss]

Yeah, the idea was to give the film a curvature across its inherent longitudinal bow which has to do with the water content of the gelatine. Other makes have that feature, too. The image shell of lenses is in most cases a more complicated form but traditionally widely opened systems, predominantly Petzval, are used picking out a smaller area from the useful circle. Film movement along the optical axis is the more severe problem than flatness. Only mechanical limitations such as a narrow guidance between glass panes can force the strip to lay as flat as desired.

I have worked with all sorts of light sources and lens designs. There is a variety of optics from triplets to eight-elements lenses. We have limelight, low-intensity and high-intensity carbon arcs, incandescent bulbs, xenon high-pressure discharge lamps, impulse light. Experience tells that the film should have a RH equilibrium of around 50 percent prior to projection and be wound emulsion in. Forces in the gate should be as small as possible in order to have a relaxed film, if one can say so. One particular observation is that prints tend to behave best, focus-wise, toward the end of the rolls. The multitude of fine scratches and cuts both in the gelatins and in the base plastic do away with a lot of tensions so that the strip stands in the gate like a board. The heat impact from the lamp twice per frame does not help the situation.

I think IMAX showed the right way with the film air-sucked to a ground and polished aperture glass. Focus and definition thanks to register pins are excellent show after show. I have wondered many times whether it might be possible to cool the film via an aquarium of some sort.

[Steve Guttag]

There are theories and then there are theories. As to gate/skate design, the notion of a fixed set of runners versus skate has been hashed a bit over the years and one can make arguments for both. The DP70 used a fixed gate yet, as shown with many 35mm shows, it didn't have a lock on film image quality. A flaw with the rigid gate is that the image is in the emulsion, not the base (or the mag tracks). So, the thickness of the film itself, uniformity thereof as well as if any sort of magnetic application had been applied (and the uniformity thereof) would change the focal plane of the image. Note, while these contributed to the DP70's struggles with 35mm image, many will claim the gates tri-radii shape didn't do it any favors. The "uniquely" shaped DP75 skate seemed to work well enough too though I didn't see anyone trying to emulate that.

Letting the runner strips be fixed, on the other hand, allows the reference point be against the emulsion of the film and has the potential for the greatest stability. In studio screening rooms, with traditional US made projectors, "straight" gates were mostly used and they too had the rigid point be the rear/emulsion side.

Straight gates fell out of favor in larger lamp situations where the film would deflect in the direction of the heat (a problem not normally noticed with the lower wattages/trim of a small studio screening room). Another issue of many straight gates is how to dissipate the heat as they will just absorb it and play into the entire ability of the gate/trap system to hold the film. Curving the gate system allow stress to be applied to film during projection that held its position better and in some gate/trap designs (i.e. Simplex, Century) to separate the heat absorbing metal from the film via tension bands/straps.

As for focus, high speed photography has shown that we focus the image where it is at its greatest deflection. It is the only real strike against 3-wing shutters as it has the film deflect 3 times...which, with small lamps is insignificant but on larger lamps can make for as less sharp though more flicker-free image.

As for sound sync...that discussion continues into the digital era too. Most projectors I've worked with are designed around a 20-frame separation between picture and sound. Most leaders (except SMPTE countdowns) also, if followed will have you set sound sync at 20-frames to give you a slight advance in the sound sync. I have no doubt that due to when these machines were designed, theatres sat 1000-6000 people, typically (even suburban sub-run theatres in the 1930s-1960s would be in the high-hundreds with projection throws over 100-feet). Pushing the sound out past the stage and getting it to the point that people didn't notice the lip-sync was out was advantageous. You'll get away with having dead sync behind the picture more than ahead of it. Psychoacoustics works when sound lags image, as in nature (to a point) but your brain will be rather quick to notice something amiss if sound leads picture (something that does not occur in nature).

[Sean McKinnon]

I always thought that having one side of the lateral guide fixed was an error because as differently slit films, different stocks, or splices came through it would push the frame to one side causing weave on screen. Having moveable lateral guides on both sides (hopefully) keeps the frame centered (as Steve said above) and should cause less perceptible weave on screen. I have not worked with every projector ever made but I have worked with all of the popular US ones and the most popular European projectors and I think the Kinoton gate runner, skate, ceramic disc design is far superior to everything else I worked with especially the Strong variants available in the late 90's early 2000's.

[Steve Guttag]

I don't know if anyone really has a lock on gate/trap/skate design. They all have their ups and downs. Simplex's lateral guide roller on the XL gates would warp in the hardening process. Each one was "unique." You can watch the image weave with the rotation of the roller (depends on the one you got as to how noticeable it is). I have not found a particular benefit to the Kinoton floating design over a rigid reference side as I've seen very steady images from both designs. I can say that lateral guide rollers seem to beat pressure guides (e.g. Cinemeccanica). As we liked to say, "Cinemeccanica put the motion in motion pictures." Some called them shakameccanicas. Every once in a while, you get a rock-steady V8 or something but it is more the exception than the rule. Their split drum soundhead also seemed like an overt attempt to introduce artifacts.

As for steady/sharp pictures, yes the Kinoton E series is way up there though if a splice goes through, that 24-tooth intermittent sprocket prolongs the duration of the image rise/fall due to the thickness of the splice. I've seen very steady pictures from Norelco/Kinoton, Century, Simplex (E7 and XL) and Christie (and even the off Cinemeccanica). Even the Norelco DP70 can put out a steady/sharp picture if you put the effort in and adjust the tension bands properly and get the lateral guides dialed in (both in position and pressure). I know that Mark G used an alignment gauge. I favored metal film with CS perfs (for 35mm). If you get everything dialed in, it should pass that film with ease. I never understood why LaVezzi only ever made their metal film with KS perfs when their VKF sprockets would handle CS perfs. If you are dead center, CS perfs are right and KS will always work if CS does.

Another truism I've found is that the Century JJ puts out a steadier picture than the Century SA (or H or C).

[Leo Enticknap]

fhabks for all the comments. Interestingly I've just tried my first full feature film (Madagascar, 2005) and I had to increase the gate tension to almost on full plus as the film was jumping all over the place on screen and pushing the gate out on the projector. Yet for my other set of films (old ads and trailers) it was ok with being in the middle setting.

I'm guessing that Madagascar is on polyester stock (likely 2383), whereas your ad and trailer reel is mainly acetate, which is a lot thicker. That would explain the gate tension difference, though I'm surprised that you had to screw it down all the way. I haven't worked regularly with an FP since the 1990s (apart from the 38E at the Egyptian from 2014 to '17, but we only used it for 16mm), but my memory is that the difference is about a quarter turn. I wonder if your pressure plate is significantly worn.

As for jumping and pushing the gate out, in the first few years after the conversion from acetate to polyester for release printing, there were numerous problems with the antistatic coating that has to be applied to the base side of these prints to stop the layers from sticking together and causing a platter brain wrap. If you go back through the early years of F-T, I suspect you'll find many discussions about this. If they got the coating wrong, it was almost like the print was coated in superglue! From around 1998 to 2001 (when I left the business, temporarily - I did hardly any release print handling between 2001 and '14), I would guess that around one in 20 prints I handled had a bad antistatic coating on at least one of the reels, which made it unplayable on a platter system. This was one of the reasons I absolutely insisted on a rehearsal/QC screening of every print we played (unless it arrived on crossover with no time, but in that case, a previous cinema must have played it, meaning that it was likely OK on that score): you had to platter it and run it to find out.

So I'm wondering if your Madagascar print has a bad antistatic layer, and that this is causing gate stickiness.

[Jerry G. Axelsson]

Hello friends and colleagues, we run FP-30:s on a weekly basis.
The gate tension for Polyester should be around the 50% mark, sometimes slightly below.
Acetate is usually 50-60% unless shrunk. With shrunk film you sometimes end up around 60-70%.

Note to oneself: Do not forget to reset the gate tension after a show. (if you are swapping films).
Excessive gate tension puts unnecessary stress on the intermittent and the outer bearing of the intermittent axis.

[Stefan Scholz]

With modern polyestar base prints and use of Polyamide gate parts, I normally run around the marked center position, or a little below on our FP 30D's.

It is actually depending on more factors, the condition of skates, pressure pad, and the spring ageing to start with.
And what kind of skates are used, they exist in polished steel, Novotex, Polyamide, and Polyoximethalene plastics. The pressure pad I found in the mentioned plastics, in bakelite, metal, and in Lignostone, the last ones being the oldest I found on FP 20s in the 1980s, and is made of densified tropical wood.
Plus the type and condition of film stock used, coatings etc.