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Posted by Ian Bailey (Member # 1752) on 02-16-2004, 10:59 PM:
 
What are the main causes of vertical picture shake and how do you go about proving it to be a mechanical fault with the projector other than watching shaky credits at the end of a show?
 

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Posted by Chris Hipp (Member # 1788) on 02-16-2004, 11:03 PM:
 
The most common cause is lack of tension at the film gate. An improperly aligned intermittent sprocket can also be to blame. Could also be a loose lens.

Post what type of equipment you have and someone can help you with that specific machine.
 

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Posted by Warren Smyth (Member # 1838) on 02-16-2004, 11:13 PM:
 
Some causes - Hooked (worn) intermittent sprocket, dirt on gate runners, unlubricated print, insufficient gate tension, strained or raised sprocket holes (which in turn can be result of excessive gate tension or worn sprocket).

If the projected picture has the framing lowered so as the frame line is just visible and the line is steady but the picture jumps, then the fault is in the print. If the line is jumping too, then chances are, the fault is at your end.
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-16-2004, 11:14 PM:
 
What kind of projector are you operating there?
The best way to see if it might be the mechanism is to run a loop of SMPTE RP-40 target film. This film is camera original and is as close to dead steady as it gets. If you run a loop of this stff and there are steadiness problems then the projector may be at fault. Its also possible a lens element, or turrett stop could be loose. Note that you could also ru a loop of I.B. Technicolor film as it is registration printed and also extremely steady.

Mark @ CLACO
 

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Posted by Ian Bailey (Member # 1752) on 02-16-2004, 11:21 PM:
 
It is a Simplex 35(model 1050) with a TU2000 turret.I have been suspicious of the gate tension as I have tried what the manual says about increasing the tension till the sound from the intermittent changes then I think you take it back a notch and I can't hear any sound change at all from the lowest tension to the highest.I can see in the gate that you can change the position of the "tesioning cam"to increase the gate tension but I am unsure if that is the correct way to do it.How do you know when the tension is correct and what do you do if your gate does not allow you to get to the desired tension?
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-17-2004, 08:42 AM:
 
Inside the gate there is an arm which sometimes is made from cast alumnium...essentially pot metal. These arms tend to flex and take a set over the years and then they stay that way causing the gate tension adjuster not to function correctly. You can also add pressure against the film going in at the top of the trap with your finger to see if that helps steady the image. If this arm is made from formed sheet metal then its probably ok and the problem lies somewhere else.

There are a number of things that can cause this problem, among them are worn intermittent pad shoes, bad intermittent, loose or bad(hooked or otherwise worn)intermittent sprocket, and on many machines there is a stopper screw that is a stop set for how far the gate closes into the trap. I suppose even seriously worn pressure pads and or film guides could also cause this but they'd have yo be REALLY bad.

Another thing to check is to see that there is not alot of excess vibration when the machine is running. This can cause sympathetic vibration of the turrett making you think there is a projector problem when there really isn't. Also check the turrett stopper screws and be sure that when the turrett is locked shut that it is not vibrating at all.

Hope this helps out....

Mark @ CLACO
 

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Posted by Steve Guttag (Member # 268) on 02-17-2004, 06:57 PM:
 
RP-40 is not the best tool to judge projector steadiness...at least not B&W RP-40. While it is camera original, it is pin registered so the target will follow the perforations which are BH-1866 rather than the proper KS-1870.

Since the projector is edge guided, variations between the perforation to the edge of the film will have RP-40 movement when it isn't the projector's fault.

35-IQ which is currently shot on color stock with KS-1870 perforations is better to judge steadiness. The best current film is Schneider's CLT test film though.

Steve
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-18-2004, 08:25 AM:
 
Steve,
On a properly set up machine I seriously doubt anyone would see any projected difference between two target films with either KS1870 perfs or with B&H negative perfs. There is also no real major tolerance difference of the edge of perf to edge of film with either negative or positive perfs. All film is made and perforated to very high tolerances, much tighter tolerances than almost any projector is capable of keeping on a day to day basis. There is one instance I can think of that might cause a problem and thats if the registration pin(s) in the camera movement are nicking the perfs and picking off a small piece of the perf. This is very unlikely with the cameras used to shoot these test films and all reg pins are normally tapered so they enter the film small and come in till they fit fully and then move the film into position. Also one pin fits fully in the lateral position and the other vertically to allow for any variation in perforations and for acetate film dinension variations. There are also some 35mm cameras out there that do use edge guidance with B&H perf stock. The tight tolerance of of the manufacture of all raw stock makes either film quite suitable for this basic purpose.

There is one case I can think of where KS perfs would be preferable and that is when checking steadiness of a machine with Positrol sprockets as these sprockets have teeth on one side that fit the full width of the perf and use the side of the perf to position the film.

Mark @ CLACO
 

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Posted by Chris Hipp (Member # 1788) on 02-18-2004, 08:31 AM:
 
I often us a loop of green band to check steadiness. Just make sure that you run a loop big enough to simulate platter use. All of the RP40 I have is so worn out I wouldnt trust it anyway.
 

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Posted by Brad Miller (Member # 2) on 02-18-2004, 12:33 PM:
 
With so many lousy printing jobs out there, I wouldn't trust a green band loop. If you just HAD to use that as a test, make damn sure it is one from the Technicolor lab.

Personally if your port windows and projector design will allow it, you would be better to slide the aperture halfway out and look at the projected sprockets. The sprockets won't lie, even if the printed image does.
 

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Posted by Steve Kraus (Member # 476) on 02-18-2004, 01:24 PM:
 
If I start a fresh loop of 35PA (RP40)..ooh baby...you'd think you were looking at a slide it's so steady.
 

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Posted by Gordon McLeod (Member # 33) on 02-18-2004, 02:04 PM:
 
If possible pull the apperture and look at the edges of the projected perfsa if the gate will allow them to be projected as there movement is a true indication of film movement
 

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Posted by Chris Hipp (Member # 1788) on 02-18-2004, 08:31 PM:
 
Mr Miller, please accept my apology for poisoning the well with my green band idea. However, since RP40 is not on the "approved" list, I cannot order any more, so I must make do with what I have.
 

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Posted by John Pytlak (Member # 331) on 02-18-2004, 09:28 PM:
 
I agree with Brad and Gordon: the most conclusive test for whether the projector is the source of the unsteadiness is to pull the aperture and project the perforations on the screen. If the perfs are "rock steady", the projector is doing its job.
 

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Posted by John Walsh (Member # 168) on 02-18-2004, 10:52 PM:
 
I'm finding some projectors aren't designed such that you can see the sprockets. Couldn't do it on a PK60D.
 

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Posted by Paul G. Thompson (Member # 655) on 02-18-2004, 10:57 PM:
 
I also agree with Brad and Gordon. As far as I am concerned, lot of test film is pure garbage.

Isn't automation the most wonderful thing you have seen to get the crap flying though the door?

What ever happened to good old days when the quality goes in before the name goes on?
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-19-2004, 12:10 AM:
 
I agree that the perfs are a good refrence if they are visible but when using RP-40 one can actually use it as a guage to meaasure jitter and weave. Hence it has a bit more meaning to it.

Mark @ CLACO
 

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Posted by Gordon McLeod (Member # 33) on 02-19-2004, 10:25 AM:
 
The same method used with 35PA of projecting a shadow on the screen and comparing it to the movement of the image can be used with the perfs and get an accurate answer
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-19-2004, 07:53 PM:
 
Gord, So how much of a perf is a quarter of a square ?

Mark
 

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Posted by Gordon McLeod (Member # 33) on 02-19-2004, 08:17 PM:
 
Measure it as % movement
 

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Posted by John Pytlak (Member # 331) on 02-19-2004, 08:57 PM:
 
I don't have a copy of SMPTE RP40 with me here in Montreal, but I recall that there are 200 squares across the width of the image, so each square is 0.825 / 200 = 0.004125 inches on each side. Therefore, a quarter of a square represents about 0.001 inch of movement. The KS perforation is 0.1100 x 0.0780 inches in size.
 

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Posted by Steve Guttag (Member # 268) on 02-21-2004, 07:48 AM:
 
Mark, you are so wrong about the image movement on 35-PA. There are several processes that go into its final outcome. First, that film stock has its perforatinos punched as 4-perf sets as opposed to release print film where it is continious punch. Then there is the edge slitting and how it relates to the perforations.

The camera used to shoot 35-PA is pin-registered, not edge guided. What showes up on the screen is a culmination of how well the perforations are aligned to edge of the film. Even the pulling of the aperture plate test will give a false projector attribute if the perforations are skewing in relationship to the edge of the film. This problem has been noted by the facility that makes 35-PA.

As to BH-1866...it is the wrong pitch for projectors, period and not a valid test. You should test with a close a material as what you are going to use. BH-1866 is the proper test for Tele-cine work though.

I have had many hundreds of feet of reject 35-PA that completely relate to the how the film was made prior to it ever entering the camera.

The current batch we have seems to be pretty steady this time. So far, all 35-IQ (magenta) have been steady and all Schneider CLT test film has been steady. That is another indication of 35-PA's guilt...other films are steady in a projector where 35-PA was not.

Steve
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-21-2004, 10:03 AM:
 
Steve,
I too have had bad batches of 35PA but not in a very long time. In fact it was back before the camera was either replaced or overhauled and 35PA was really horrible as per frame to frame tolerance. The present batch we are using is actually superb. And while the camera being used used to make 35PA definately does not use edge guiding...no B&H type, Mitchell, or Panavision movement does, but there are in fact many professional cameras in daily use that do rely on edge guiding for lateral steadiness. Those include Arriflex 2A,B,C, 3C, and all B&H Eyemos that serve as crash cams, all Eclair Cameflex's, almost all ultra high speed cameras and some of the effects cameras out there. The fact that these cameras not only rely on it for lateral steadiness but the fact that many of these cameras produce images nearly as steady as a pin regestered movement is clear proof that the accuracy of the perfs is excellent. As for the pitch there is no argument that it is different but it only means that there may be one perf against a tooth on a 16 tooth sprocket at a given time and this actually makes the film in itself more of an acid test. Unfortunately there are those that do look at the perfs rather than measure steadiness.....
In fact Steve I use my Schneider CLT film as a refrence to compare and evaluate any 35PA that comes in. They have all been excellent, were they not we wouldn't be using it.

Perhaps John P. would like to chime in on how accurate the tolerance of the perfs is kept in relation to the edge of the film. I'm sure that Kodak is extremely proud of how tight they are able to keep this on a daily basis.

Mark
 

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Posted by Gordon McLeod (Member # 33) on 02-21-2004, 07:57 PM:
 
"Unfortunately there are those that do look at the perfs rather than measure steadiness....."
That is the correct way to measure it since the 35PA is not usable for that function
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-21-2004, 10:46 PM:
 
So Gord, How many inches of perf equals .001 inch of movement?
Mark
 

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Posted by Steve Guttag (Member # 268) on 02-22-2004, 12:39 AM:
 
Mark, I have actually had John measure some 35-PA due to its unsteadiness...he found it to be within spec. It still shook on screen..you could tell where you were in the loop due to picture movement.

It hasn't been that long since I had a bad 200' roll of 35-PA and the manufacturer of 35-PA regularly complains about the lack of tolerence on both the perforation skewing and slitting width and wishes the allowances were cut in half.

One of the ways he checks his camera is to shoot the target, back the film up reshoot it and then shoot it again...if alignment is perfect there should only be one target on the film not a smearing of three...they always come out as one.

It is interesting to note that Schneider CLT is not on Kodak stock (I don't think 35-IQ is either).

I agree that the last batch of 35-PA we received was pretty steady though.

Steve
 

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Posted by Mark Gulbrandsen (Member # 72) on 02-22-2004, 09:45 AM:
 
Steve,
Thats the standard double exposure test used for all cameras and its a really good way to verify camera and film, but more difficult to figure out which is bad when things go wrong. Its pretty much SOP to do with any rental camera before it goes onto a production.

In over 20 years of using the film I just have not had the shake problem you mention when running RP-40, only the frame to frame steadiness problem which no one could do anything about at the time. What projectors did this occur on for you? I normally get it in 200 foot rolls, perhaps twice a year..... If John found the film to be within spec I'm sure it was ok. You really need either an electron microscope or projected optical comparator to check anything of this accuracy. Kodak may even use other means to check accuracy.....hello John P., are you out there......

Mark
 

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Posted by Gordon McLeod (Member # 33) on 02-22-2004, 12:15 PM:
 
One of the Kodak engineers had us completly releive the band of a JJ so the perfs completly could be projected for registration and slitong tolerance tests
 

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Posted by Tim Reed (Member # 137) on 02-22-2004, 12:29 PM:
 

quote:

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Thats the standard double exposure test... Its pretty much SOP to do with any rental camera before it goes onto a production.

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