This post was written by Keith Dawson for UBM Tech’s community Web site All LED Lighting, sponsored by Philips Lumileds. It is archived here because the All LED Lighting site has gone dark. This material is Copyright 2013-2015 by UBM Americas.

2013-10-16

Dimming to Warm

Late to the party, Cree recently announced a dim-to-warm option for its LMH2 LED modules. Many suppliers offer this now, but is it what we want?

Dim-to-warm mimics the dimming behavior of incandescent and halogen lighting: The color temperature of the light drops (becomes redder and "warmer") as the light is dimmed.

Cree's Sunset Dimming module is separate from LED and driver, according to LEDs Magazine's coverage of Cree's announcement. Here are Cree's product page and data sheet for the LMH2 family.

Cree's own drivers work with various dimmer technologies, and the company maintains a list of compatible dimmers from other suppliers. Sunset Dimming can be used with all of them to alter the dimming behavior of a "TrueWhite" LMH2 module: Its color temperature drops from 2700K to 1800K as it is dimmed from 100 percent down to 1 percent. The CRI stays above 90 down to 2170K, and remains above 80 at the bottom of the dimming range.

What Cree is hoping to accomplish with this feature is to make the LMH2 more attractive especially in the hospitality industry: restaurants, bars, hotels, conference facilities, and theaters, and also in "high-end residential fixtures," LEDs Magazine reported. The LMH2 family now includes modules offering from 850 to 4000 lumens with standard dimming that Cree has re-christened "WhiteLight." The Sunset Dimming modules reach 3000 lm.

Other players
Cree is far from the first to offer dim-to-warm. Here are a few of the others in the game:

Is dim-to-warm what we want?
In June we gauged the sentiment of this community by asking in a quick poll how LED lights should behave when dimmed. With 43 people responding, 47 percent said the color should not change; 21 percent opted for "it should become redder"; and 23 percent admitted to not having considered the question much.

In my research I turned up what might have been one of the earliest proponents of the idea that LEDs should mimic incandescents and drop down the CCT scale as they dim. That would be Kevin Willmorth, owner of Luminique LLC and a longtime lighting designer and product developer. Willmorth claimed in this February 2012 post that "when LEDs first emerged" his had been one of the voices calling for lighting systems that could dim to a warmer CCT.

But the point of that post was to recant his earlier opinion. He said that over 20 years, until the advent of the LED, he had come to use halogen almost exclusively, preferring its clean white light to "that yellowy dinginess" that is the incandescent. He dislikes the way a dimming incandescent distorts color, although by definition its CRI remains at 100.

I asked Lukas Sturm, co-principal of Lumen Studio, how much demand he sees for dim-to-warm lighting. Sturm said his consultancy largely deals with commercial clients, and he doesn't see much of the hospitality industry. With that caveat, he said the subject rarely if ever comes up from clients or prospects. He opined that the lighting industry hasn't done a great job so far in marketing the feature, and wondered whether Cree's entry might change that picture. Sturm was aware of dim-to-warm products from Philips and Juno, but seemed surprised when I listed a few of the others I had come across.

What do you think? Will Cree's entry move dim-to-warm into the mainstream of people's expectations for LED lighting, or will the feature remain just another nice-to-have in a complete product line?

Related posts:

— Keith Dawson Circle me on Google+ Follow me on Twitter Visit my LinkedIn page, Editor-in-Chief, All LED Lighting