Film-Tech Forum ARCHIVE: Dimmer Advice

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Posted by Martin McCaffery (Member # 37) on 06-23-2015, 02:27 PM:

We're going to do some remodeling (and rewiring) of our single screen 1941 theatre and I'm looking for dimmer advice and recommendations.

Currently, we have no dimmers because we use the original flourescent lights, mounted on the sides. Very dim theatre. There are blue incandescent wash lights behind the flourescents. And aisle lights in some of the seat endpieces. No curtain lights, though it once had spotlights for the curtains.

We want to go all LED. Will add work lights and dimmable curtain spots and want dimmable house lights. Automation will run through a Christie ACT. Being able to remotely control from downstairs is a plus.

What dimmers do you suggest? Any spotlight suggestions?

Posted by Louis Bornwasser (Member # 3063) on 06-23-2015, 02:48 PM:

I also have that sales flyer in my file. Stapled to it is a business card for Morley Kahn and Dolby with only New York addresses. This is before the move to San Fran. Only employee to make the move besides Ioan Allen was Stacey Rehm. (Then, of course, there was George Finkhousen.)

Posted by Scott Norwood (Member # 30) on 06-23-2015, 03:13 PM:

Not all LEDs will dim fully. Usually, they will dim partway (to 20%-ish) and then just go out. Also, LEDs often flicker when dimmed. Either get the good LEDs that dim properly without flickering or go incandescent.

By "spotlight," do you mean "followspot" or "leko" (aka "ellipsoidal spotlight")? For the latter, pretty much everyone is using the ETC Source 4 series, which are generally considered to be the best (they come in different focal lengths, so you need to figure out which one to order). Not many movie theatres have followspots; if they do, they generally have something crappy like the "Comet" series.

I would suggest talking with someone from a stage lighting company. These people know what you need and won't try to sell you non-dimmable wall sconces or something like that. They can also rent you equipment to try out before you commit to buying anything.

[ 06-23-2015, 05:41 PM: Message edited by: Scott Norwood ]

Posted by Louis Bornwasser (Member # 3063) on 06-23-2015, 07:54 PM:

Contact Kelmar Systems in Huntington Station NY. Ask for Thomas Mohr.

The issues are reliability, UL approval, ease of connecting to D Cin automation and suitability for LEDs. He has fought all of the battles.

Posted by Steve Guttag (Member # 268) on 06-24-2015, 07:12 AM:

Kelmar does have an add-on kit for their dimmers to make them more compatible with dimmable LEDs. Note, you will likely have to shift your preset way towards the bottom end of the scale. Tom can advise on lamp brands/types that have worked better than others. As Louis says, he has fought the battles.

Though not posted on their web site, they now have 0-10VDC option for dimmable LED fixtures

They also have their LCS-LAM that is an LED adapter module for conventional dimmers to make them deal with replacement LEDs better (reduces you odds of the flickering/inconsistent dimming.

Moving Image Technologies has also done a bit with the LED thing including now making their own LED light fixtures entirely.

http://www.movingimagetech.com/product/alf-led-light-fixture/

If you are redoing your entire system, it might be worth abandoning running 120V fixtures only to drop it back down for the LEDs and instead go to low voltage.

http://www.movingimagetech.com/product/lms/

This is definitely a change in the industry where I couldn't imagine building a new system not on LED. The lamps have gotten rather good in the last 12 months in terms of most everything and from a maintenance standpoint, the is a lot to like as well as cost savings on burning incandescent versus LED.

Posted by Carsten Kurz (Member # 5396) on 06-24-2015, 07:51 AM:

It's not easy to go the LED way, depending on your long-term-scope. General 230/120V Lamps can not be dimmed reliably with current dimmers. You may be able to find a working combination if, as others suggested, you follow the guidelines of experienced manufacturers/service companies. But in general, getting a nice dimming curve is not easy with common dimmable lamps. Plus, LED lamps do fail, and within a couple of years, you may not be able to find replacements that will work with your existing set. It's possible that it will be easier/cheaper to buy a completely new set in 5 years, but you can never be sure.

The only way to do dimming right with LED is by using dedicated modules that support real PWM dimming. They are available, but a higher cost than general LED bulbs, and all these solutions today are non-standard items - could be a problem to repair/replace them in a couple of years.

If you expect to spent money on a solution that keeps the LED promise of 10-20 years painless operation, that is not easy, because it is still new technology, especially when it comes to nice dimming. I would hate to invest a couple of thousand dollars into a new dimmer+lamps+control system and then seeing the auditorium lights go up and down unevenly, flickering, noisy, without the important smooth last percents of light.

You could also look for DMX based solutions, because DMX will always be around, and there will always be compatible LED products for DMX. That makes you less dependent on a single manufacturers product line.

- Carsten

Posted by David Buckley (Member # 2600) on 06-24-2015, 06:08 PM:

quote:
You could also look for DMX based solutions ... That makes you less dependent on a single manufacturers product line.

I'd opine that is excellent advice. DMX is becoming more and more a part of architectural lighting installations.

Even so, a very common problem with... "economic" DMX LED devices is the lowest 1% of the dim, the bit between off and not quite off. Many devices handle this terribly, with a "snap" on or off happening.

Posted by Jack Theakston (Member # 4484) on 07-05-2015, 02:25 PM:

Funny, we had NO problem switching over to LED in our 1928 theater, where we replaced over 1,000 bulbs. Most of these (about 600) were in areas that did not dim, but in all of the other places they did dim, we had absolutely no problem getting down to an acceptable zero level. This is largely because for our application, we had a consultant from the company we purchased the bulbs from. Many power companies have subsidizing programs for LED replacement. We ended up paying something like 10% on all of the bulbs we purchased.

Depending on if the area you're lighting is recessed or not, you may just want to go with LED strips, but there are also LED tubes that replace fluorescent, which are essentially LED strip in a plastic tube.

Posted by Marcel Birgelen (Member # 6801) on 07-05-2015, 06:13 PM:

It looks like you got a bunch of LEDs with a bunch of power supplies that do support a nice linear dimming operation. This is by no means standard, as many LEDs will behave erratically if they're not fed with the expected input voltage.

quote: Carsten Kurz
You could also look for DMX based solutions, because DMX will always be around, and there will always be compatible LED products for DMX. That makes you less dependent on a single manufacturers product line.

DMX sounds like a great and durable solution, but the extra cabling can be cost-prohibitive. Also, DMX gear is usually more expensive, more bulky than other manufacturer-specific solutions. DMX isn't really focused on this market (yet). Maybe one should come up with a decent DMX-over-power solution, it would be a welcome alternative alongside hobby protocols like X10.

Posted by Mark Hajducki (Member # 1732) on 07-05-2015, 07:33 PM:

quote: Marcel Birgelen
Maybe one should come up with a decent DMX-over-power solution

DMX over ethernet exists, as do ethernet to powerline adapters- so it should be easy enough to come up with a combined solution.

For DMX-over-power to work the sender and receiver would have to be on the same phase or close electrical circuit. That would put a major restriction on the use of such a system, especially in live theatres (the major users of DMX).