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Topic: Procedures for cleaning lamphouses and rotating bulbs

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 09-27-2000 12:03 AM

Excellent point, Randy. That is designed for the assembly to move the lamp forward for flat films when the format is switched to optimize light. I've seen people think the same thing about that one.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 09-27-2000 03:55 PM

Dustin:

Check around. Maybe you could borrow a meter from an equipment dealer or service engineer, or share a meter with other theatres in your circuit/city:
http://www.kodak.com/US/en/motion/newsletters/notes/june2000/pytlak.shtml

If you have a good photographic "spotmeter", you can calibrate it against a known 16 footlambert standard as measured by a "real" screen luminance meter.

Adjusting luminance and uniformity "by eye" can be tricky. In general, "brighter is better", as long as you don't get so bright that shutter flicker is an issue, or get so much energy that you cause heat damage to the film (as in Randy's blistered film above).

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 09-27-2000 06:46 PM

Personally, I'd err on the side of caution when focusing the lamp and stuff.

When doing a CFS, we just usually go for the most output we can get 'cuz they're so inefficient. On Christie it's a different story...
Christies are so efficient you probably won't need to crank them all the way up.
When I get the lamp focused I always check it again. Sometimes I even back off just a "hair" to be sure. THEN I set the "Don't touch this @#$%&^* button" controls.

When focusing a Christie I'd rather have it be just a hair bit dim than burn the film.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 09-28-2000 01:56 AM

Randy,

What size Christie lamphouse are you speaking of? Are any of these perhaps 6 or 7k units? I'm just curios as I've only worked with Christie's lamphouses up to 4500 watts, but even on a test I did with the lamp cranked down to a hot spot, there was no film damage.

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David Kilderry
Master Film Handler

Posts: 355
From: Melbourne Australia
Registered: Sep 1999

posted 09-28-2000 06:21 AM

In all the lamp manufacturers instructions I have read of late (most produce a detailed book on their products) NONE recommend the rotation of the xenon in normal use unless the envelope blackens .

The advances in quartz used in xenon lamps means the incidence of blackening is far reduced.

After a career of being a "rotator" 4 years ago I stopped and lamp steadiness has improved throughout the lamp life.

David

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 09-28-2000 11:00 AM

First, John, thanks for the compliment. I'm doing a similar presentation at Show East. I'd like to give Brad the file afterwards to have on this site. I guess I should do an instructional video next...

On the burning film issue, one consideration is additional filters. Some 4kw systems offer insertion type filters as an optional item and not standard in larger wattage systems. That filter makes a big difference in heat on the film, especially if the focus is too "tight".

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 09-28-2000 11:16 AM

The other factor relating to heat damage is the density (darkness) of the image, and the type of print film. Very dense (dark) images absorb much more radiant energy than light images. Black-and-white print film is much more likely to suffer heat damage because the silver image absorbs not only visible light, but infrared (IR) heat energy as well. The dye images in color prints absorb visible energy, but are fairly transparent to IR energy above 750 nanometres. But some color print are processed in "silver retention" processes to give them a higher contrast, "gritty" look, with lower color saturation (e.g., "Evita", "Saving Private Ryan" and "Seven"). The silver left in the film image will absorb infrared energy, and make these prints more sensitive to heat damage from a misaligned lamp or poor heat filtration.

It's always a good idea to run a loop of an old trailer with dark scenes several hundred times after any lamp adjustment, just to be sure you won't cause "hot spot" damage to prints, as in Randy's example.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 09-28-2000 03:19 PM

Not 100% sure which size. I think it was a 6K but it might have been a 4500.

Actually, the damage I showed you was because the autofocus mechanism broke and caused a malfuction which fried the film.

There have been incidents of somebody flicking the switch and walking away, though. Just about the same amount of damage.

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Rory Burke
Expert Film Handler

Posts: 181
From: Burbank, CA, USA
Registered: Jun 2000

posted 09-29-2000 12:53 PM

Paper towels on a refllector? Did I read that right up there? I was always trained and practiced using cloth baby diapers or some gentle type of cotton material. Should i stay with this practice or are scruffy paper towels good enough as it is?

Rory

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 09-29-2000 01:08 PM

Rory:

Pat Moore also noted that paper towels may be too harsh, and scratch the coatings. Like you, he prefers soft cotton. I guess lens cleaning tissue would work well too.

Edmund Scientific sells a variety of optical cleaning cloths and solutions for lenses and mirrors:
http://www.edmundoptics.com
http://www.edmundoptics.com/IOD/Browse.cfm?catid=250&FromCatID=174

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 09-29-2000 08:51 PM

I usually use Kimtuffs and wipes

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 09-29-2000 10:54 PM

Yeah, I mentioned using paper towels, but I should have qualified that by saying; "...but use soft cloth if avaiable."

I only thought of paper towels because our company would never pay for cloth towels, and you can only ask for cloth rags from friends for so long.

The old-timer who showed me how to clean the Ashcrafts insisted on using diapers.

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Jeff Moore
Film Handler

Posts: 7
From: Lakewood, CA, USA
Registered: Sep 2000

posted 10-06-2000 02:46 AM

Earlier in this topic, I noticed someone who runs the lamp life out to 6,000 hours. How common is this? Our engineering dept. mandates that the lamps are changed out at no more than 20% past warranty. Roughly, at 1728 hours, running at 90 amps, with a Christie CXL-30 lamp. I've often wondered how much longer they would go?

By the way, maxi-pads (un-used ones of course) work well for cleaning the reflectors, and there always seems to be an abundance of them in the theatre storeroom.

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 10-06-2000 07:18 AM

Over the years I've seen policies all over the map on xenon bulb usage and replacement policies. There are no real "standards" and I think that's because xenon bulbs, being hand made items under some very stringent conditions, can vary as well. I think it depends on the experience of those in charge.

For every "Yes, rotate", you can find a "No, don't rotate". There are about as many xenon lamps that never have their current changed since installation as there are lamps started at 80% of their nominal value and then adjusted upwards to maximum current throughout their usable life.

Change and removal policy is one of those things as well. Let the lamp go until it's too dark, or remove it at warranty plus 20 or 30 or 50%?

To me, the bottom line is: Is there sufficient light on screen? I try to equip a theatre so light levels at the end of a bulbs "normal" life will still be at (or damn near) SMPTE guidelines. That's really not too hard to do -- good old "headroom".

As long as the lamp a) strikes reliably, b) the quartz envelope is generally clear, c) the arc is steady (non-wavering), and d) there are proper light levels on screen while running within the operating spec's of the bulb, I'm not concerned if the lamp has 2000 or 4000 hours on it. I get very cautious with quartz envelopes that are dark or very cloudy, as I feel they become more of a hazard.

One guy's opinion, right?

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 10-06-2000 08:02 AM

I agree with Pat Moore that the light on the screen (exactly 16 footlamberts, of course), no flicker, and reliability of ignition are what counts the most. But, AFAIK, all the lamp manufacturers warn that the risk of explosion increases dramatically as the lamp is run well beyond its rated life. Gordon McLeod states the dilemma well: is it worth saving a bit of money on lamp replacement, if a lamp explosion takes out a reflector, and cancels several shows? It's a gamble that may not be worth taking.

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