8mm Forum: How do films burn in a projector?

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Posted by Robert Perkins (Member # 3847) on July 31, 2013, 06:34 PM:

Hi. I googled this one but haven't found an exact answer.
I was playing with my new(old) projector tonight and the film got stuck and a single frame started to burn. Studying the innards I see that the light source is at least a couple of inches away from the gate. Does the whole gate assembly get hot enough to burn the film if it doesn't keep moving? Or is it the concentrated light like a magnifying glass burning a piece of paper by focusing sunlight to a small point? thank, bob.

Posted by Hugh Thompson Scott (Member # 2922) on July 31, 2013, 07:02 PM:

Film burns in a projector Robert, because to generate the amount
of light needed,a certain amount of heat is also created for to
be able to screen a movie. Modern lamps have a certain curvature
in the reflector, that enables them to focus the light onto the gate
aperture, not all the heat is dissipated through the rear of the
dichroic reflector, and some does heat up the gate. Some projectors have a glass heat shield to absorb this additional heat,as
well as an additional shield which is used on some projectors for
still frame viewing. As a test to feel how much heat comes through the gate aperture, place your finger just in front of it while the machine has no film in, and you can feel it.

Posted by Robert Perkins (Member # 3847) on July 31, 2013, 07:20 PM:

Thanks, Hugh.
I'm looking at finding my own approach to telecining the 8mm home movies we recently found. I had read that the project and video method is not very good and tried it myself tonight. I think I'm not going to be able to control the speed of my projector well enough to get rid of flicker.

So what I'm really wondering now is will the shutter protect the film from burning if it blocks the light into the gate at the same time the film has stopped?

Posted by Hugh Thompson Scott (Member # 2922) on August 01, 2013, 03:03 AM:

Film will only burn in the gate Robert if there is a problem, like
jamming, or at the end of the film reel.When your projector is showing film at the recommended speeds of 16-18 frames per
second of at 24, rest assured your film will be quite safe.

Posted by Robert Perkins (Member # 3847) on August 01, 2013, 05:28 AM:

Hugh, I'm planning on converting the projector to a DIY frame-by-frame telecine machine. Most of the projects I've seen are using low power/heat LED's for their light source. I'd like to be able to use the original 100w bulb and reflector (I don't have the electrical know-how to install a control circuit for the LED's and I'm doubtful about finding the right LED's anyway.)

I guess the easiest thing to do is to see what happens when I stop the film with the shutter between the light and the gate.

Posted by Dominique De Bast (Member # 3798) on August 01, 2013, 05:47 AM:

I must be missing something. What's the point of having the shutter between the bulb and the film ? Doing so you will have no picture, nor on a screen or a camera that you would put instead of the lens (if I understood well your project). Without heating filter (which gives you a less bright picture), you will burn your film with a 100 watts bulb. In the silent area, the films had variable speeds but there were often shoot at a speed higher than 16 fps (the minimum to avoid flicking), to avoid projection accidents as at that time the filmstock was inflammable.

Posted by Martin Jones (Member # 1163) on August 01, 2013, 05:54 AM:

Robert,
I'm assuming your lamp is the standard MR16 size.
You can replace the 100W lamp with a 20 W of the same size...

http://www.tlc-direct.co.uk/Products/LXM69G.html

Just use a couple of layers of ordinary "copy paper" stuck to the front as a diffuser. This will not burn the even when the film is stationary.

or you can use an LED equivalent....

http://www.tlc-direct.co.uk/Products/LTMR3W.html

which replaces directly.. no control circuit required... same provision for diffuser.

If not MR16 there may still be a domestic 20w with the same size.

Look for suppliers in your country. These are common domestic items. I have used both successfully.
Martin

Posted by Robert Perkins (Member # 3847) on August 01, 2013, 06:12 AM:

I never did get anyone to positively ID this projector

here but I can see that neither of those bulb types will fit, Martin.

Dominique, from what I've read about other frame-by-frame telecine projects, a certain amount of time is required in between captures for the image to be recorded either to a computer or the camera's memory. Somewhere between one and 2 seconds I think. So in between one capture and the next, the film will have to be stationary. So, I'm thinking that either I have to turn offf the light or maybe arrange it so that the shutter stops the light from getting to the gate.

Posted by Robert Crewdson (Member # 3790) on August 01, 2013, 06:24 AM:

I came across a very early thread the other day, where an agent for a film transfer company had damaged two customers films by cleaning them first. The project and copy method is not very good, but I wouldn't trust any of my home movies to anyone.

Posted by Robert Perkins (Member # 3847) on August 01, 2013, 07:37 AM:

Martin, are you saying that the lower wattage bulbs are sufficient because instead of projecting onto a screen, I'll be directing the image into a web cam or other digital camera?

BTW, I should mention here that my two overriding constraints are money (I know times are tough all over but check the news about Greece) and the availability of things that are thought of as common. Two things for instance off the top of my head: In ten years here I have not been able to find a battery terminal cleaner for my car. Also I bought a pair of hiking boots here that I was never able to find a pair of replacement shoelaces for. And some really sad news: The last McDonalds in Thessaloniki closed yesterday.

I've also seen some "professional" results for film transfers that I feel confident I can do better.

And I just noticed your signature, Martin and am happy to find someone with a similar interest [Smile]

Posted by Hugh Thompson Scott (Member # 2922) on August 01, 2013, 07:58 AM:

The projector is the EUMIG MARK S Robert, I thought I'd mentioned that. It is a reliable machine,very heavy, 100watt
light output with variable speed and amp.output of 2 watts.,As for adjusting the speed, don't try to do it when the projector is in forward,it must be stationary before sliding the
little switch, wait a minute, then switch forward projection.

Posted by Robert Perkins (Member # 3847) on August 01, 2013, 08:05 AM:

Thanks, Hugh. Almost every search I did here and elsewhere on the web for "Eumig Mark S" returned a result with a number after the "S". And I haven't wanted to pry into it to find out but do you know if there are elastic belts inside the arms for the supply and take up reels?

Posted by Martin Jones (Member # 1163) on August 01, 2013, 08:10 AM:

Yes, Robert, you have read that correctly. One of the main problems of doing "Frame by Frame" is ensuring that you use a lamp that is "dim" enough not to overwhelm the camera, yet of o "colour temperature" as close to daylight as possible. Both my suggestions fit the bill nicely.
The other is ensuring that the camera can see exactly the area of the image in sharp focus: this depends greatly on what projector and camera you wish to employ.
See this thread from 2008...
http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=8;t=000936# 000000

I currently transfer by two methods: frame by frame with a modified Cinerex and "on the fly" using a modified Eumig. Both used low wattage bulbs and view the film directly in the gate.
The Eumig range need a fair amount of work to convert for Frame by Frame, since the current drive motor cannot be used.

And it can't be all bad in Greece if your last Macdonalds has closed... they apparently serve the same rubbish everywhere!

Martin

Posted by Hugh Thompson Scott (Member # 2922) on August 01, 2013, 08:21 AM:

I couldn't comment on the spool arms Robert, as I've never had occasion to look, if it is a rubber band,it must be epecially good
as they do seem to last That is a very
good suggestion from Martin, except the lamps these projectors
use are the 12v 100watt quartz iodne two pin bulb, as all the
reflectors & condensers are in situ. Some people have removed
the original fittings and use higher power lamps with reflector.

Posted by Martin Jones (Member # 1163) on August 01, 2013, 08:36 AM:

Correct, Hugh. It's the FCR lamp, which is a G 6.35 base 12v 100w.

http://www.ebay.co.uk/itm/Package-5-New-Lamps-G-6-35-12V-20W-w att-JC-Halogen-Landscape-LightsBulbs-/350587853499

This is the 12v 20w domestic equivalent , which is widely available and I have also used on occasion. Even if the filament is not exactly correct in position, the base could probably be adjusted. It doesn't really mater, as a simple diffuser as described before will help to offset that.

Robert, if you email or pm me with your email address I'll send you some information on the whole subject. I've done this for others before, but its better done off-Forum!
Martin

Posted by Hugh Thompson Scott (Member # 2922) on August 01, 2013, 10:22 AM:

You're in good hands Robert.

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