I couldn't agree more with Guy's excellent response to this matter. I have spent significant time and energy studying the colour quality issues of LED fixtures for the film and broadcast market and I can see from Guy's post that we have read many of the same studies and tech papers. He's right... a perfect LED does not exist, and it probably never will for the exact reasons listed. Our needs are too small for the big players like Lumileds or Osram and the such to really drop the quest for ultimate household lighting to make a good looking video light. The market for production lighting is small, probably less that $20m annually worldwide where for comparisons Phillips sold over $100m in LEDS a month in 2010, and the big LED revolution had not even started last year. You and your camera are small pickins to distract any major research effort.

Progress in LED production lighting will come from the small manufacturers that are already entrenched in our industry. They will innovate and find ways to make the LED work for us because they have something to lose if they do not evolve with the technology of LED which will surly dominate the lighting world in the immediate future.

I am in total agreement with Guy's post but I would like to but I would like to take note of his use of the term "remote phosphor". Although the use of the term in the post is 100% correct it can be misleading to those without such a well versed background on LED lighting. All white LEDs that use a phosphor are technically remote phosphor devices however the use of "remote phosphor" is often used to describe LED fixtures that use the technique of placing the colour changing phosphor outside of the actual LED itself.

This technique also called "cold phosphor" is used by Osram/Mole in their MoleLED and PRG in their new mini single LED production light. Some reviewers have given this technique very high marks for colour rendering and I do personally agree that the above mentioned fixtures are probably among the best LED colour renderers I have ever seen.

So for those of you that only read the product literature understand the difference as it is a significant one.

Cheers
(BTW I promise to finish up over at the Colouroflight.com soon, I'm the world's least prolific blogger I guess)

You really need to test with the meduim you're using. Video cameras have traditionally been pretty blind towards the green in standard fluorescents, whilst with film the green does come out pretty strongly. You need to test with the camera you're using to see how it's responding with the greens, some of the new digital cameras may pick up green because they not limited to rec 709.

Very true. And its not limited to the camera sensor. Lenses do not equally transmit all wavelengths of light. If you take a lens and put it on test equipment such as a Richter autocollimator and push different colored light through it, you will see differences in the collimation points and differences in the ability to resolve light on a focused plane. True, they are small, but they are there. Same thing with a Lens Test Projector. These differences exist between brands and also within a series for one manufacturer. For old lenses, there are differences between two copies of an identical lens.

The bottom line is that each situation is unique. There is a reason that DPs shoot test footage as part of pre-production. Each step may introduce a variation, from the light source, to the actors or the scenery's reflection, to the lens, the sensor or the film type, through the chemical processing or digital treatment.

Bob: check out the thread Color Meter Weirdness. There is a lot of technical info. I started that thread. I have the Sekonic 500C. What I can tell you is that the CT diffs exist between film and digital modes for discontinous light sources. For the sun, tungsten, and HMIs, they are the same (more or less, if you use a meter you will note that even a fraction of an inch in movement will change the reading).

The digital mode is basically a computed calculation that attemps to approximate the Correlated Color Temp for LEDs/flouros. Is Sekonic's algorithm correct? What are their assumptions? Who knows. But its better than nothing, even though it may not be accurate. At a minimum, it can be used to compare different LEDs or compare two examples of the same LED to see if they are consistent.

I can't believe that nobody, especially Guy Holt, has yet to mention the newest and potentially the best solid state lighting technology: LEP or Light Emitting Plasma. This seems to be an answer for a lot of the LED drawbacks, while providing a more efficient use of power than a tungsten or even an HMI lamp.

Its still a bit pricey and has limited distribution, fixture types, and wattage options to date. But it clearly has a lot to offer, especially in regards to the spikey color spectrum of LEDs. Hopefully, there will be a price drop after the Early Adopters clear out the R&D investments and manufacturing ramps up.

I have seen LEP in action in entertainment fixtures and personally (electric considerations aside) I'm not sure if it will find much traction.