Film-Tech Forum ARCHIVE: How frequently to adjust lamps

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Posted by Martin McCaffery (Member # 37) on 08-28-2016, 05:33 PM:

Solaria One with CDXL-21S1 lamp.

We replaced the lamp on June 19. I has 270 hours. We set up the lamp at 14fl. About two or 3 weeks later I had to adjust it again as it was down to about 11.5.
We're now back down to 11.5 and getting caution notices that the LiteLoc target is not reachable (actually, the yellow warning light is blinking off and on right now (11.3 fl seems to be the tipping point).

I'll readjust the lamp tomorrow. I expect some break in performance change, but have never had it like this. Am I doing something wrong or is this expected behavior?

Posted by Steve Guttag (Member # 268) on 08-28-2016, 10:21 PM:

It is generally best to adjust the lamp early in life to keep it maximized but by about 500 hours, you'll see that the change in focus starts to stabilize.

However, if you ever find that your lamp is running at or above 90%, it is going to decay much faster and will progressively lose its light output and there is nothing ou can adjust to get it back.

S2K projectors, like the Solaria 1 are going to be particularly susceptible since they have smaller apertures and need the extra short arc gap for the light efficientcy. Once the arc opens up, you'll never get it back.

The other problem fighting you is the small projector and its inability to cool larger lamps very well. Below 1800 watts it does much better than 1800 watts and above.

Posted by Marco Giustini (Member # 4544) on 08-29-2016, 12:52 PM:

Martin,

when you say 'adjust' do you mean align?

Posted by Martin McCaffery (Member # 37) on 08-29-2016, 01:16 PM:

Yes, align in the Lamp Adjust window.

I was able to get it to 12.7 fl with LiteLOC on. But that is also running at 100% (80A). Given what Steve posted, and what Christie's Best Practices recommend, this is a formula for burning up the bulb way to quick.

Should I abandon LiteLOC and see what I can get manually. Will this require more attention as the bulb ages?

Posted by Mark Gulbrandsen (Member # 72) on 08-29-2016, 01:48 PM:

I have to wonder if your projector has enough light for your screen once you pass a certain point in a lamps life. How big is it and what surface do you have?

Mark

Posted by Steve Guttag (Member # 268) on 08-29-2016, 05:21 PM:

Note, there is LampLOC...which is Christie's auto lamp alignment (extremely good) and LiteLOC which merely adjusts current to keep the "number" at the desired level. The number has not direct correlation to foot-Lamberts but presumably when you measure the light and declare THAT is the right amount, you can let LiteLOC so that it will hold it there. LiteLOC will jack your lamp all over the place, current wise to achieve its desires. It doesn't care that 100% is as far as one should go...if the projector allows 110%, it will over drive your lamp. Now starting in 4.5.0.11, one can uncheck overdrive to keep the lamp in its allowable range.

You should find a level that you can maintain throughout the lamp's life, even if it isn't 14fL and run it there. There are some that do indeed put it in an overly bright level and leave it there for the rest of the lamp's life and NEVER increase the current...so it decays and by the end, it is running a bit dark.

Posted by Martin McCaffery (Member # 37) on 08-29-2016, 09:47 PM:

Mark: 26x13ft, matte screen.

Steve: So I guess I should try without LiteLoc. Without an actual light meter, I really don't know what's hitting the screen, and because of some eye problems, can't really judge what is too bright (and everything usually seems dim to me). Nonetheless, I do think our picture is better than the commercial theaters in town.

Posted by Steve Guttag (Member # 268) on 08-30-2016, 04:58 AM:

So it is a dreaded 2:1. How do you handle it for the two primary formats? Do you pillar box Flat and Letterbox scope or do you fill it on both formats or just fill it on Scope or just fill it on Flat?

Just remember, you have just 9000 lumens MAXIMUM on day 1 with a brand new lamp running at 100% and only only have that if you happened to choose the same lens that Christie did when they determined its lumen output (some lenses are more efficient than others). Odds are, if you don't letterbox your scope image, that 12fL is MAXIMUM you could target and that only works if you do that from day 1. Odds are, your best solution is to target 17fL for flat and then hold onto that level for both Flat and Scope (scope will be dimmer but let the lamp level be the same for both and let LiteLOC compensate for lamp aging). But with a lamp like the 21, it is going to age VERY fast as you approach 100% power...all extra-short arcs do.

Posted by Martin McCaffery (Member # 37) on 08-30-2016, 08:07 AM:

Yup 2:1 (1941 theatre with proscenium). We letterbox scope, though do make it a little wider than 1:85. Arthouse, so we do other ratios, and the occasional 35mm still.

Lots of scope pictures recently, which may be why the dimness has been extra noticeable to me. I guess we just do the best we can until the glorious day when we toss the Solaria, which, given their lifespan, will only be a few years from now.