Film-Tech Forum ARCHIVE: How do you check for scratching caused by your projector?

This is topic How do you check for scratching caused by your projector? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=011686

Posted by Alastair Bowlie-Evans (Member # 8327) on 07-22-2014, 05:33 AM:

Not sure how other guys do this, but what I'm doing at the moment is running a loop.
The loop takes approx 5 seconds to run around the FP-23 I'm messing with at the moment.

Ive arranged an old roller to guide the loop around the front of the mech fixed to the lens-table, the loop is fairly slack.

A rough calculation indicates that it would have run around 720 times in 1 hour.
(I wonder if the splice will hold that long!--Jackroe tape)

Its been running now for about half hour, looks OK so far at 300 times....

I'll stop at the hour (or when the splice fails) and check for any issues on this relatively unused piece of filmstock....

Posted by Pete Naples (Member # 761) on 07-22-2014, 01:59 PM:

Sounds fair to me.

Posted by Mike Blakesley (Member # 26) on 07-22-2014, 02:19 PM:

If you've run it 300 times and don't have a scratch yet you probably aren't going to have one.

I'm guessing you have been scratching prints....maybe the problem isn't in the projector but in one of the rollers (not turning, or a piece of schmutz jammed in there or whatever).

Tell us what problem you are trying to solve specifically.

Posted by Leo Enticknap (Member # 534) on 07-23-2014, 12:43 AM:

To answer the question in the thread title, I shine a flashlight on both the base and emulsion side of the film as it comes out of the bottom of the machine, heading towards the take-up reel, as soon as possible after the changeover. If I see any scratch I then look at the film coming off the feed reel to check if it's there as well (unless I noticed the scratch when checking the reel on the bench, noted it in the condition report and therefore am expecting to see it). If it is, the scratch arrived on the print and there's nothing I can do about it. If it isn't, I've got a problem.

Thankfully, I've never been in the position of noticing a new scratch being inflicted while projecting to an audience, failed to find the cause or found that it can't be fixed without stopping the projector, and thus having stop the show or damage an entire reel.

Posted by Alastair Bowlie-Evans (Member # 8327) on 07-23-2014, 01:54 AM:

Mike--

In answer to your question--No, not ever scratched a print, this machine is new to me and been renovating it, Its something I do to check a machine out.
Just thought I would ask how others do checks like this.

I was doing this as a precaution against any issues down the road....

The loop ran for the full hour, the splice survived--and appears still pretty solid surprisingly,--better than on other mechs such as Kalee Running a loop through a Kalee, for an hour the splice would have either failed or been on its last legs.

720 odd times through the mech, apart from light scratching at the edges and sprocket-hole areas, there's no apparent other marking at all.

Guess this mech is OK to run prints on.

Posted by Brad Miller (Member # 2) on 07-23-2014, 11:29 AM:

If you have scratching in the sprocket hole areas and the edges, you will be destroying the SDDS and SRD tracks.

Posted by Randy Stankey (Member # 64) on 07-23-2014, 12:06 PM:

Considering what Brad says, check your pad rollers and sprockets and you should be good to go.

Wouldn't hurt to double check your trap alignment and tension, as well.
That kind of goes without saying...

As to how I would check a projector and film transport for scratching and damage issues, I start at the payout, follow the entire path through the system until reaching the takeup and just "be the film." If a roller doesn't roll the way it should, if a guide doesn't guide the film the way it should or if anything touches film that shouldn't, realign, repair or replace the offending part.

The concept is simple but the process is very detail-oriented but, as I said, just "be the film."

It sounds like you've done pretty well, so far.
Keep up the work and keep film alive! [thumbsup]

Posted by Alastair Bowlie-Evans (Member # 8327) on 07-24-2014, 03:29 AM:

Oh dear--Think Ive been mis-understood.....

When I say 'light scratching' I mean--Just that. The surface is no longer shiny, checks with magnification indicate the surface both sides is equally dull, having thousands of tiny longditudinal marks, only noticable when the film is viewed at an angle to the light.
Sprocket-holes appear unaffected, although bound to be, but left me Electron Microscope in my other lab! [Big Grin]

There is no obvious loss of emulsion or Loss of any of the Digital tracks.

If there Wasn't Light Scratching after 720 passes as described, then there would be something wrong!

By the action of Any Projector--There'll be this sort of wear. The Gate is the source, any flexible surface clamped between two other faces under spring-tension, accelerated and stopped 24 times a second will suffer Some form of wear This is Inevitable and unavoidable.

Another source of wear of this description could be the lay-on roller--which in this case clamps the edges of the film on the soundhead drum, Better than BAF/Kalee where its clamped on the Picture areas.....

Wear is defined as surface abrasion and scratching in this sorta scenario.
700 odd times through a clamped film-gate is bound to cause some wear like this.

What is the expected life of a print in passes through a machine? Ive heard 300 times quoted somewhere, but this does seem rather low....

Perhaps the word--Scratching is wrong for this description and the source of the confusion--Maybe I should have used 'Wear'....

The Philips FP-20/30 (kinoton) machines with their plastic curved gates I'm pretty sure are one of the kinder to film than something like a Cinemecclunker with its hardened steel gate and pressure-pads, guessing slight damage to the contact faces of one of those would wreck a digital track on one pass....
(This is just an observation, not saying that a Cinemeccanica isnt a good machine)

Posted by Louis Bornwasser (Member # 3063) on 07-24-2014, 06:33 AM:

Remember in any projector, the only thing that touches the image is the drum in the soundhead. Some designs don't even have that one.

Posted by Brad Miller (Member # 2) on 07-24-2014, 11:05 AM:

That is absolutely incorrect Louis. In a Simplex 5 star and various other models as the SH-1000 soundhead there is the "dirt embedder roller" that does an excellent job of collecting dirt and mashing it into the soft, just-heated-and-softened emulsion.

I know you're a Century guy though and it's easy to forget about those unfortunate people who have to work with those boat anchors. [Razz]

Posted by Buck Wilson (Member # 5885) on 07-24-2014, 02:59 PM:

Good ol' Simplex 5 star. I had 4 too many of those. One of them I just COULD NOT get to not do that, though I lessened it to a great degree.

Sigh. Great design there. "Hey, let's put a grippy tension roller here, and we'll have it run on the image area. It's rubber, it can't hurt anything!!"

Posted by Barry Floyd (Member # 385) on 07-24-2014, 03:03 PM:

Our old SH1020 soundhead was notorious for collection bits of crap and embedding itself into the film. We cleaned them every night, but once every couple of months, we'd end up with a scratch from start to finish.

At the indoor theatres, most scratches looked like a hair line on the screen. At the drive-in, a scratch looked like a freakin' telephone pole.

Posted by Alastair Bowlie-Evans (Member # 8327) on 08-03-2014, 09:49 AM:

Hmm--I wonder Why many makers of projectors--many highly respected makes, had steel or other materials, for lay-on rollers clamping the film in the sound-head in the visible picture area....

Many of the 30's 40's and 50's designed machines were like this, my own Kalee 12 with its BAF GC-3 type soundhead is a prime example of this, and the later Kalee 19-21 with BAF 83 and 943 soundheads--just the same and (to me) silly error in design--

'Lets put a steel roller to iron crap into the emulsion every time the film passes through the machine, Brilliant!'.....

Cinemeccanica and Kinoton/Philips at least didn't do that. Film is clamped in the edge/perforation areas.....