Ribbon Light Praticals

[Gerald King]

Does anyone know where I can get Ribbon Lights that would look clean on picture? 

[Phil Rhodes]

When you say ribbon lights, are you thinking of the 8-10mm wide flexible strip with LEDs on it?

Assuming you are:

If you want white, there are a few manufacturers who make high-CRI stuff. Literibbons are widely used but rather expensive. I have some Yuji LED stuff which performs very well in tests with a UPRTek CV600 colour meter, and looks nice on most of the cameras I've used it on. These types have reasonably consistent batch to batch colour and are available in specific colour temperatures. You can go even cheaper on eBay where there are listings for LED strip described simply as "cool white" or "warm white" with CRI above 90. Assuming the CRI claim is accurate, they should be vaguely reasonable. I haven't tried them.

Below that there's the standard warm and cool white stuff. Stuff described as "warm white" tends to read rather greenish-yellow and unhealthy-looking on digital cameras in a way that probably isn't that useful. The cool white can look cold and cyanish in a way that recalls industrial lighting and might find application on a sci fi movie or in an industrial setting.

The coloured stuff is potentially useful; I've made quick and dirty lights out of the green strip to illuminate greenscreens. There's a need for a bit of caution with the blue stuff which can read magenta on at least some digital cameras. This happens because of the wider problem that most coloured LEDs are very monochromatic, which is to say that they're a tiny spike on the spectrum of visible light. This means that they can sometimes produce strange and unpredictable results, particularly if you try to illuminate brightly-coloured objects with them. They're totally usable, but test.

The RGB strip (as well as assemblies of separate red, green and blue strip) may be useful. Remember that mixing very narrow red, green and blue sources does not create an unbroken spectrum of white light, it creates three spikes on the spectrum which may look like white light to eyes and cameras but, again, may behave oddly when used to illuminate brightly coloured objects. Most of the low-cost commercial controllers intended to operate RGB strip use pulse width modulation, risking flicker, and are not suitable for film and TV work. Most (not all) RGB strip, or RGBW strip with the extra white channel, is wired in a way that can't easily be operated with a stack of standalone dimmers to provide colour mixing. (If you want to do this, look for "common cathode RGB LED strip." Most is common anode.)

Phosphor LEDs are better. Some LEDs, including the pinkish-magenta-purple colours, are made using blue LEDs driving phosphors. All white LEDs are made this way. This is good because the phosphor has a wider, less spiky spectral output and is less likely to cause strange colorimetry problems. Pinkish-magenta LEDs are usually made this way. Red and green phosphor LEDs also exist, but are not usually found in LED strip. You can tell the difference usually because non-phosphor LEDs have clear encapsulation which leaves the inner electronics visible. White LEDs look yellow while other colours tend to look close to their emission colour.

Do not stick rows of LED strips side by side; they will overheat. If you buy the very cheap stuff, run it at two thirds power or less for better life. It's not exactly expensive; just use more for more brightness. This is doubly true for phosphor LEDs where the phosphors tend to degrade with excessive heat, turning white lights purplish.

Do not run it directly from camera batteries or anything else that's more than 12V. Most LED strip is designed for 12V and 14.4V lithium ion batteries may be more than 17V fully charged; this is an overdrive sufficient to cause overheating and damage.

You can use low cost DC to DC converters found online to drive LED strip from variable voltages. You can use the adjustable voltage output to dim the strip, although the cheaper stuff is not very consistent and will go blotchy when dimmed in this way.

That's about all I can think of about LED strip. Does that help?

P