Safe Dimmers For LED Video Lights

I created this video to help shed some light (pun intended) on LED's and Dimmers. You can read it below in text form also.

Click the Video above to see the Dimmer Comparisons and to learn about LED fixtures and Dimmers

Last year I was in a situation where I was using two 4ft Quasar Cross Fade LED's and the Director called for a smooth lighting cue. Now I don't usually use dimmers but I did have a cheap router control speed box in the bottom of my bag which for halogen fixtures can work in a pinch. Unfortunately with LED's they don't work very well. I was less than impressed with the results and while the shot worked out in the end, after the shoot I embarked on a journey to find a better solution for LED dimmers. During my research I found out it's fairly complicated and you have to be a little careful when using dimmers with LED's.

My first stop was the Quasar website were they have a list of approved dimmers for their fixtures. They had standard DMX setups from RatPac which are great with Cintenna transmitters but of course these are professional units so are more expensive. They did list one however that was a build it yourself option, it was a Lutron CL Series Dimmer switch.

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During my dimmer research, I discovered Dave Donaldson’s YouTube channel called Grip Tips as his episode about 1000w watt dimmers came up in my google search. I watched that episode and although his dimmer wasn’t for LED’s, I did really like his version of home made dimmer particularly because of the rain cover (I’m in Seattle) and his “build it right, build it once” - mentality regarding quality. I definitely tend to overbuild my own stuff.

So I went out to Home Depot and grabbed the parts that Dave Donaldson had on his list and I also grabbed that Lutron CL dimmer switch.

Ok, so that was all back in October 2017, here we are in April 2018 and I just finally made time to build these dimmers. I popped back onto Grip Tips to refresh my memory on how Dave built his dimmer and I saw the recent comment asking about dimmer compatibility with Quasars, which is what prompted me to write this blog post.

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Turns out the LED dimmer situation is a racket. There are literally hundreds of different LED bulbs and fixtures within the consumer and film world, and the standards are all over the place. Because of this, using the correct dimmer is really important. Now, most LED’s I use like SkyPanel and Litemat come with an onboard dimmer but there are some fixtures like Quasar Crossfades or the LED Fresnels I've been using that do not have a dimmer built in, so it's a good thing to have in your kit just in case.

Also, when shooting on location, the bulbs in the lamps are almost always LED or CFL these days, it’s good to have a dimmer capable of correctly handling those situations. If you are on a location and there are LED or CFL lightbulbs in the house lamps, it doesn’t mean you can dim them, they have to specially say they are dimmable to avoid flicker.

I keep both dimmable LED's and low wattage Tungsten practicals in my kit. I’m still a fan of real Tungsten because the light quality is so good, so I use those whenever possible. The main reason I'll use LED in practicals is if we need it dimmed but don't want a color shift. The other reason is if we want a daylight balanced practical (or somewhere in between).

Ok, let’s talk Dimmers.

For this test, I used 3 different dimmers. The first one is a cheap router speed control box which you’ve no doubt seen or used before. They run as cheap as $20 and are really crappy to be honest.

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The next one is a "Dave Donaldson" special. It’s a Lutron 1000w Halogen dimmer switch. As Dave mentioned in his video, it was under $100 for all the parts.

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The last one is also a "Dave Donaldson" special but using a Lutron CL 150w LED dimmer switch. It should be noted, this switch can also handle up to 600w Halogen. Again under $100 for all the parts.

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Before we look at the dimmer tests, I wanted to give you a quick rundown about the LED fresnel I’m using. It’s a product from VisionSmith that I’ve really enjoyed using over the last 6 months. The product is called ReLamp and comes in 300w up to 2000w tungsten equivalent output but with only 50 to 270w power draw depending on the unit you choose. Essentially it’s an “LED Globe” for lack of a better term. It has the same pin configuration as the Halogen globe inside and Arri or Mole Richardson Fresnel and you simply pull out the Halogen and put in the LED unit. It comes in Daylight or Tungsten. I use them in Arri fixtures and I personally only own the Daylight versions.

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There is currently no Bi-Color option. I would imagine the focus was to produce a globe with maximum output with accurate color rendering. Bi-Color LEDs almost always have lower output and because this is essentially a “globe” you can just swap tungsten or daylight in a matter of seconds. But that topic is a another debate entirely.

While I am using a 650w ReLamp for this test, the dimmer results would apply to Quasars as well, I don’t own any to test but I’ve used the cheap router speed control box with the Quasars as mentioned in the very beginning and can bueno!

The Tests:

First up was the cheap router speed control box. It only dims down to about 20% and it has a definite pop on the low end where nothing happens as you turn the dial. It also suddenly pops brighter when trying ot increase the light intensity. Basically unusable if you need the light to start at 0% intensity or end at 0% intensity. See the video above starting at 6 min 20 sec to see this crappy "dimmer" in action.

I compared each dimmer not only by eye but also with a color meter to see how the output compared between dimmers. Usually you will lose a small amount of output with dimmers in the mix. The unusual thing about this cheap router speed control box is it made the light fixture put out a slightly HIGHER output than no dimmer at all. I can’t imagine this is a good thing.

Next up I tried the Lutron 1000w Halogen dimmer. It has a surprisingly smooth transition when dimming but also doesn’t quite get to 0%. I would say it’s really close though maybe down to 1 or 2%. No flickering that I can see. The output did drop slightly by about 300 lux when the dimmer was at full intensity. See the video above starting at 7 min 15 sec to see this dimmer in action and the color meter readings.

Finally we have the Lutron 150w LED dimmer switch. When using this dimmer the light is very smooth coming up and down and while it also doesn’t get to 0%, it also gets down to probably 2% or less. So dark in fact that my color meter couldn’t even register because the output was so low. The light output did drop by about 200 lux. See the video above starting at 7 min 45 sec to see this dimmer in action and the color meter readings.

Ok, if you watched the comparisons in the video,, you might ask, what’s the deal? The Lutron LED Dimmer and the Lutron Halogen Dimmer seem to get the same results. Well, here is where shit gets real. Just kidding : )

From my research, and I know I’ve only scratched the surface on this topic, LED’s differ from Tungsten or Halogen bulbs as the bulbs don't iluiminate due to electricity stimulating a filament, rather we could say they are more similar to a fluorescent fixture which has a ballast. LED’s don’t have ballasts per se but instead something called a driver. These drivers vary for every brand of LED, from consumer LED light bulbs to pro video fixtures. So while the Halogen Lutron dimmer might work on the ReLamp LED globe that I’m using in this test, it might not work as well on say Quasars. According to the comment on the Grip Tips dimmer episode, Dave says it does flicker at the low end on Quasars where as the exact same Halogen dimmer build used here does not flicker with ReLamp globes.

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So at the very least the Halogen dimmers will have different results on different LED fixtures whereas the dimmer designed for LED’s should be consistent throughout brands. And in fact on the Quasar website they specifically say “Lutron CL series” which is the Lutron Dimmer series that supports CFL and LED, probably because they know it’s the safest/reliable option.

So my advice? Simply make a few LED dimmers and then you won’t have to worry about it. You’ll have an LED safe dimmer that will get you the best performance possible for lighting cues. You can use regular dimmers if you want to, but results will vary and you could be damaging the LED fixtures over time and with the price of LED’s in the film world, I’d rather spend $70 to build an LED compatible dimmer switch than ruin an LED fixture costing $100’s or $1000’s of dollars.

One last thing I want to mention because it totally confused me and I don’t have a definitive answer for it yet. You may wonder why the Lutron CL LED dimmer says it is approved up to 150w for LED or up to 600w Halogen.

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The way we’ve always approached these things in the past was if the wiring, connectors, and the switch were rated for a wattage, we were good to use fixtures up to that wattage, for example 1000w dimmer could handle up to a 1000w Fresnel. Apparently with LED technology there is a lot more going on behind the scenes. I was heavily interested in this because I also own a 2k ReLamp LED which draws up to 270 watts, well above the 150watts this dimmer switch is rated for. Lutron makes options up to 250 watts but it does get more expensive, closer to $70 for just the dimmer switch. So if anyone has answers to this question and want to leave advice in the comments, it would be appreciated.

I realize the actual test in this blog post was very short and the explanation was very long, but it is a complex subject so I hope it at least helps with preliminary questions regarding the do’s and don’ts of LED dimming.

Here are some useful links to articles about LED's and Dimmers.

General Article about LED Do's and Don't for Dimming

10 Things you MUST know before you dim LED lamps

Lutron Tech Document for LED and CFL Lamps/Fixtures

These articles have helped me understand this topic a lot better. Here is the Lutron Dimmer Catalog which really helps explain this stuff as well.

Lutron LED Dimmer Catalog

Finally if you haven't checked out Grip Tips before, it's a really solid YouTube Channel, especially if you are just starting out. Here is a link to that channel. Big thanks and shout out to Dave Donaldson for his episode on dimmers and for adding to quality online filmmaker resources. As someone who also really enjoys sharing knowledge, I know how much time goes into creating educational content. Keep up the great work dude!