Film-Tech Forum ARCHIVE: Using Gels to Correct Faded Film

This is topic Using Gels to Correct Faded Film in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Charles M. Allen (Member # 4315) on 09-11-2008, 03:19 PM:

Hi All,
I am interested in purchasing and testing out some gels to quasi-correct film prints that have faded pink. I am the Chief Projectionist at the George Eastman House and we have many prints that have succumbed to pink fading, some are really pink, so are less pink. I am wondering if anyone has experience with the gel (probably cyan gels) option for pink fading correction, where I might buy gels, or who I might contact that has some experience with this issue.
Thanks so much,
Charlie

Posted by Kenneth Wuepper (Member # 1174) on 09-11-2008, 04:14 PM:

Charles,

Hillary Charles wrote:
"Rosco makes a series called CalColor, the various colors of which are designed to particular wavelengths. Their 15 Cyan (1/2 stop) #4315 does a good job of "restoring" cyan to the image. Since it takes away only 1/2 stop of light, that's not objectionable, and its effect on the white parts of the image are minor."

All filters in the beam between the film and the screen will reduce the clarity of the image. If the color balance is very disturbing, a small loss of detail may be a good trade off.

The best place to introduce the color filter would be between the lamp and the film. These filters must survive great heat and could be very expensive. The dichroic type filters are used here as in the light path of a color film enlarger.

Perhaps you might inquire of someone at the Kodak Marketing Education Center as they are very knowledgeable on these topics.

KEN

Posted by Christian Appelt (Member # 1067) on 09-12-2008, 09:15 AM:

Gels do not work very well because they fade quite fast and diminish image quality.

There is a thing named "Color Rebalancing Filter" which was designed to compensate some typical fade types in Eastman color prints during projection.

I can recommend it, although it will not work with all faded prints. If you have a vintage print that looks almost black and white, no filter can bring back color. From my experience, no filter will do much good with prints that have faded to a bright pink. You get best results with prints that still have adequate density and have faded to a brownish tone.

The original filter was introduced by a now defunct German company called Cinema Technologies, and they had two types of filter for different stages of color fading.
These were 100x100mm high quality optical flass filters, made by Rodenstock IIRC, made to withstand the heat of strong projection light. I believe the present distributor is Wittner Cinetec. Ask Daniel Wittner about article no. 5002 "Color rebalancing Filter", last time I looked it cost about € 125.

service@wittner-cinetec.com

You will need two as I assume you do changeover projection. If you cannot get it, send me a message and I'll look up the adress of the guy who invented that filter, maybe he has some left from the original production run.

If you don't want to buy these special filters, you can do some tests with light blue filters for still photography. Make sure you buy glass filters, not the resin type like Cokin!

I have used KB-12 blue filters (B+W) in an emergency case (faded 1967 print arrived instead of new print) and simply taped these to the back of the projection lens. If you have a bright picture to start with (we had 4kW for 7.5 metre scope width), the light loss will be acceptable and the lost density is restored.

Be careful - the filters should not be taken off without cooling off for a few minutes, they could crack or you could get your fingertips burned.

With 16mm, filtering makes little sense because few projectors give enough brightness to compensate for the light loss.

Posted by Mitchell Dvoskin (Member # 751) on 09-12-2008, 09:16 AM:

This has been discussed endlessly on the various 16mm film collector sites ever since this guy started selling his filters on eBay. The general consensus is that filters don't work with any but the most lightly faded prints. Occasionally, the filter will provide a more pleasing color tint than red/pink, but they do not restore or balance the color in a faded print.

Posted by Christian Appelt (Member # 1067) on 09-12-2008, 09:28 AM:

Yeah, I saw his eBay auction. This is what you get with a simple blue filter. Sometimes it looks OK because it puts back some density, sometimes awful. I like his example from THE BIRDS where I would definitely prefer the unfiltered image. But to be fair to the seller, $16.95 is not that much for three simple filters, is it? [Smile]

But this is not the filter I was referring to.

Posted by Jim Bedford (Member # 4) on 09-13-2008, 09:25 AM:

Hate to say it, but the filter you're looking for may only be available from the guy who sells X-Ray glasses, board stretchers, sky hooks and buckets of knuckleballs.

Posted by Louis Bornwasser (Member # 3063) on 09-13-2008, 12:09 PM:

Don't forget "light amplifying crystals" from the biggest supporter of d-cinema. Louis

Posted by Frank Angel (Member # 248) on 09-13-2008, 06:02 PM:

We used some rosco cyan gel after hours of testing, and to parapharase Mitchell, you can't make something from nothing. If the color isn't there, it isn't there. We found a filter with just enough density to take off a little of the red, but there goes your white balance. We were still running carbon arc so the filter was hung in the lamphouse as far front as possible but still had to be replaced about every show....usually would last only for 3 or 4 reels.

And as had been stated, you CAN'T place them in front of the lens, at least not standard theatrical gel because it is not made optically clear; you will find the resolution degredation unacceptable.

The only real solution for faded prints.....get the studio to STRIKE NEW ONES. Or play the DVD on a real expensive digital projector.

Posted by Tony Bandiera Jr (Member # 2365) on 09-15-2008, 07:23 PM:

I ordered a set of those gels Mitchell linked to from the guy on Fleabay. I do a lot of old 16mm stuff that has faded and it should be interesting to see how well the gels work. I will be using them on the lens. Screen height is about 14 feet and throw is 80 feet.

I'll try to give some sort of qualatative estimates of loss of focus, resolution, etc. with the filters.

Posted by Jack Theakston (Member # 4484) on 09-21-2008, 02:31 PM:

In a nutshell, the reason that filters don't work is because you're simply subtracting more light all around, not adding color to where its necessary. So you may end up with somewhat muddy blacks again, but the side effect is that the highlights are all going to be green/cyan/whatever color filter you use.

Posted by Matthew Bailey (Member # 601) on 09-21-2008, 09:41 PM:

Just got back home from being evacuated from Ike. I think a RGB laser projection lamphouse would be better because some of the possibilities is adjusting the lasers for color correction of discolored motion picture film.