Kinoton FP 38 E - 16mm Lamp Current

[Phillip Grace]

Hi all.

I need a recommendation as to the maximum lamp current I can use to screen 16mm from a Kinoton FP38E. Hoping someone here can help, as the manual has no information. Empirical answers are welcome. Our machine has a 7000w lamphouse, with the large heat filter, and chilled water cooling for the gate. We have been running it on 82 Amps for years with no issues. Both the film and the projector survive feature length runs. I think it was set up for 12 foot lamberts. There is also a small slip-in heat mask that goes just behind the gate for 16mm. Now somebody wants an image about 4 times the size to match the DCP 1.85 screen height. Can it be done? What experiences has anybody had above 82 Amps?
Any and all opinions welcome.

Thanks.

[Steve Guttag]

The current isn't the issue per se, but related. It is all about the heat. And, with a 7KW lamp, your arc size is so large compared to the aperture, you have Etendue issues already. That is, raising the current isn't going to get you lots of light. It gets you lots of heat. You'd probably get more light from a 3KW lamp running full out at 110A (presuming a UXL-30SC or equivalent and a LOT less heat on the film. Of course nobody wants to change the lamp just for the film format.

The highest I've run on 16mm is a UXL-40SCH...which is a 4KW, high-output lamp (shorter arc, more efficient. It gets you about 20% more light than a standard UXL-40SC but without any more heat).

Consider, a 7KW lamp has about a 10mm arc gap (compare that to the size of a 16mm aperture...it's HUGE). A short arc 4KW lamp has a 7mm arc gap. The UXL-40SCH has a 6.4mm arc gap, which is still big for a 16mm aperture. You may even find that some of the digital cinema lamps (with suitable adapters) will get you more light as they also have very short arcs. I believe the CDXL-45 has a mere 6mm gap.

So, as to what I have personally used without known damage. I have used the UXL-40SCH, with chilled water (18c), with a typically current set to 110-130A, depending on lamp age. I have more using 3KW lamps running between 100-110A, depending on the venue and lamp age.

Note, these venues, by and large have 10-30fps capability, which means the shutters are reducing the open-time

An FP38E with a 24/25 shutter and an MDE intermittent/drive will have an 87-degree opening.
The same projector with a 10-30fps shutter on an MDE drive system will only have a 69-degree opening. So, my theatres will get less heat on the film than one with just a 24/25 shutter.

I have another theatre that uses 4KW lamps (UXL-40SC) but have the FPS intermittent drive.

For comparison, the 24/25 shutter on an FPS intermittent/drive gets a 103-degree opening shutter (better than 50% light transmission).
The 10-30 shutter for FPS is an 81-degree shutter (or nearly has efficient as the 24/25 MDE shutter.

So, as you can see...it isn't just a matter of "how much current can I run?" It is a matter of how much heat can I put on that dinky little piece of film.

If you are really curious and have some scrap film/leader. Splice it into a reasonable loop, say 10-feet (because we always measure film width in mm but length in feet), preferably, dark or black, and let it go for a few minutes or a dozen or two passes. Look for any embossing or other heat damage. Then you'll know.

FWIW, I also deliberately undersize my 16mm images compared to 35mm for some of the reasons you are bumping into. It is a lot harder to get light through 16mm and it is starting with less film to begin with. Blowing it up rarely makes the presentation look better.

[Ryan Gallagher]

I think it depends a bit too on from whom the request is coming from. If it is from the filmmaker team, and you are inclined not to honor it, sounds like Steve's given you lots of valid reasons they might "accept" for stating that you are unable to project at that size without losing brightness for the safety of the film itself due to heat loading with your 7K lamphouse.

If the request is to establish a new normal from the venue management you might have a harder conversation or set of choices/changes to make to increase the brightness and size on screen considering you are working with that 7K lamp.

[Phillip Grace]

Steve, thanks for your very informative post.

I was puzzled at first by your reference to arc gap versus aperture size, then it occurred to me that it is about how the reflector "sees" the light source, and how the light is directed. Deep reflector, more side-on than a carbon arc. Makes use of the length of the arc, rather than the surface of the crater. Etendue is also a new term. Something to read-up.

Our FP38E's were installed around 2001, and have 10-30 FPS variable speed, so would probably have the less efficient drive and shutter. In terms of gate temperature they are certainly the coolest-running machines I have encountered.

The show in question involves super-imposing the 16mm film image over a video image, apparently to explore the interaction between the two. It is a scaled up version of an artwork which would normally be seen in a much smaller gallery environment, delivered from portable equipment where every parameter can be individually tweaked to the taste of the artist. It is booked for one screening only.
The short answer for us would be to scale the video element down to match our 16mm image, which would mean a more predictable brightness match.

It happens that the 16mm image appears very small in the chosen cinema, so I am inclined to try enlarge it to meet them half way. In the light of your experience I will run some tests with a loop of black spacing, and step up the lamp current in small increments to see if there is anything to be gained in our situation. (Trusting that the emulsion will blister before the gate melts - he said with a grin). There seems to be a reasonable amount of head-room above our normal 82 Amps.

Thanks!

[Ryan Gallagher]

If you were really in a jam and had two digital projectors and a classroom 16mm projector. You could have a life feed 16mm classroom projector fed to one of the digitals... and the video on the other. Not quite the same literal hyrid they are hoping for, but would solve the sizing/brightness concerns perhaps.

[Tony Bandiera Jr]

If you were really in a jam and had two digital projectors and a classroom 16mm projector. You could have a life feed 16mm classroom projector fed to one of the digitals... and the video on the other. Not quite the same literal hyrid they are hoping for, but would solve the sizing/brightness concerns perhaps.

Ryan, the whole point of the exhibit seems to be correlation and interference patterns between the 24fps film shutter (with single, double or triple flash) and the 30ish fps of the video image. Using a second digital projector to "telecine" the 16mm defeats the whole premise.

I did enough oddball setups in my time at UCI (including "Chelsea Girls" and a few shows were we used my video projector to superimpose subtitles over a 16mm and 35mm film) to see what they're looking for in this exhibit.