International projectionist (Jan-Dec 1954)

jection room. The most frequent cause of this damage is in the valve rollers of the magazines, particularly the upper magazine, which is the first point of contact between projector and film after it leaves the feed roll. Dirt, oil and small pieces of film can accumulate at this point so as to prevent the free turning of the rollers, even preventing one or more from turning at all. Another frequently-found type of film damage is nicked or broken sprocket holes. This was the kind of damage mentioned in the letter referred to in the first paragraph of this article. Such nicks usually indicate too much tension. The rub, of course, is what caused the tension? New prints in which the emulsion is not fully set, when exposed to the heat of the gate, very often become sticky and create tension which, in turn, causes the nicks as the film goes past the intermittent sprocket. Once the print has been seasoned a little, this trouble is eliminated. Excessive tension at the film trap causes wear on both the projector movement and film. The sprocket teeth of the intermittent are more quickly worn out of shape. Tests by Eastman Kodak indicate that complete, equalized trap tension in excess of 16 ounces is unnecessary and only increases wear on film. Settings as low as six ounces, in some cases, seem to give a steady screen image. Another cause of nicked sprocket holes, and also of completely broken mm^tmm.m -i i • i r Bgp \m'^mp*wm^*W^'^*M-'-»'it t -I film, is faulty threadiing ot the projector which results in the loop being lost at one of the sprockets while framing. When the excessive tension at the film trap is the basic cause of nicks in the sprocket-hole area, the damage is actually caused by the teeth of the intermittent sprocket which can be worn into a hook-like shape or develop other malformations as a result of excessive tension when the film is pulled down. A tooth of this type will tear small pieces of film from the pulldown edges of the perforation. Knife-like edges on the teeth of the intermittent sprocket is another type of tooth deformation that results from contact with the inside walls of the intermittent guide or shoe. Such teeth make small straight cuts parallel to the edge of the film on the pulldown edges of the perforation and well in from the corners. These small cuts can quickly lead to the breaking-off of the edge of the film. "Runoffs," which are, of course, the gashing of the track and picture area, occur when film jumps a sprocket because of a stiff splice or some similar reason. It can also result from faulty threading. In addition to defacing the picture, these repeated gashes weaken the film in such a way that subsequent bending of the edges will often break it. In order to minimize the danger of runoffs, it is advisable to check regularly the clearance between rollers and sprockets to see that rollers are hold :-mmfMrm • i 1 1 Four samples of unsightly changeover cue marks sometimes found at the end of reels are shown above. This type of damage is not nearly as common as it was some years ago and is generally found on old prints that have seen a great deal of use in many theatres over a long period. Tension adjustment on the nevi^er projectors has been greatly simplified by the coneshaped tension springs as illustrated above. Excessive tension from the film trap can cause much wear on the projector and prints. ing the film properly in place but without pressure. Prints are often encountered where the film is bent between the perforation and one edge. Known as "idler cramping," this type of damage can be especially harmful with brittle film and when the bend is against the emulsion side. Long edges can be broken off completely. Usually starting at an edge break or loosened corner of a splice, this trouble most often occurs on the first pad roller of the intermittent loop. Bad splices — splices where a proper joint is not made and splices that are out of alignment — are a principle cause of "beefs" from exchanges as well as from projection rooms because they lead to extra work or else to torn, broken or gashed film. "I want to know what kind of splicer some projectionists use," one inspector asked. "Do they have a bench splicer like the Griswold or do they splice by hand?" In answer to this remark it can be said that not every splice on presentday film is going to be perfect or hold indefinitely. Exchanges which inspect prints hurriedly or don't inspect them at all, or even, as in some areas, go so far as to "bicycle" them directly from theatre to theatre, have themselves to blame when bad splices cause serious (Continued on page 28) 10 INTERNATIONAL PROJECTIONIST • FEBRUARY 1954