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Author Topic: Picture Shake Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 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?  |  IP: Logged Chris Hipp Phenomenal Film Handler Posts: 1462 From: Mesquite, Tx (east of Dallas) Registered: Jul 2003 posted 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.  |  IP: Logged Warren Smyth Expert Film Handler Posts: 158 From: Auckland ,New Zealand Registered: Aug 2003 posted 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.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 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?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 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  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 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  |  IP: Logged Chris Hipp Phenomenal Film Handler Posts: 1462 From: Mesquite, Tx (east of Dallas) Registered: Jul 2003 posted 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.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 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.  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 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.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 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  |  IP: Logged Chris Hipp Phenomenal Film Handler Posts: 1462 From: Mesquite, Tx (east of Dallas) Registered: Jul 2003 posted 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.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 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.  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 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.  |  IP: Logged

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