r-g-b flash?

[hjulenissen]

I would like to gel my flash for the occasional shots where you want to limit the amount of gear/intrusion and keep the overall mood of the existing light. But I never get around to it. I guess there are enough parameters to worry about...

Did anyone ever think about (or see) a flash that could vary its color temperature? Having 3 smaller bulbs, each filtered by corresponding filters (somewhat like the Philips Hue home lighting system), where the contribution of each is under software control sounds like a neat thing.

At the bare minimum, fiddling with gels could be replaced by a great big dial on the back of the flash called "Temperature [Kelvin]" (perhaps a smaller one called "tint"). Even more relaxing would be an ETTL-extention that allowed the camera to "see" the general ambience temperature of the scene, dial up corresponding settings in the flash, and ensure that heavily lighted objects/shadows had the same color temperature as the scene average (or highlights or some other sensible statistic).

-h

http://www.meethue.com/en-US

[Jim Kasson]

Did anyone ever think about (or see) a flash that could vary its color temperature? Having 3 smaller bulbs, each filtered by corresponding filters...

Interesting idea.

If using Xenon tubes, efficiency and size would suffer. The smaller the chromaticity range in the output, the more efficient you could make the system. If a straight-line approximation to the black-body curve were adequate, you could get away with only two light sources.

If using LEDs, you could have a small, efficient flash with three nearly spectral emitters. However, there would be a likelihood that some metamerism problems would surface with the spectrally peaky primaries.

Jim

[David Sutton]

Most folks I know have gone to variable colour temperature LED studio lights.

[wolfnowl]

Most folks I know have gone to variable colour temperature LED studio lights.

Exactly what I was going to suggest.  Here's one: http://fiilex.com/

Mike.

[BobFisher]

Those may work in some static environments, but not in a lot of situations where speedlights are being used. 

I'd expect that colour temperature tuning will be the next development in some of the smaller LED grid lights.  Problem with continuous light is that it doesn't have the same action-stopping capability of flash.

[Slobodan Blagojevic]

... Did anyone ever think about (or see) a flash that could vary its color temperature? Having 3 smaller bulbs, each filtered by corresponding filters (somewhat like the Philips Hue home lighting system), where the contribution of each is under software control sounds like a neat thing....

Pssst... patent it before someone else does

[hjulenissen]

If using Xenon tubes, efficiency and size would suffer. The smaller the chromaticity range in the output, the more efficient you could make the system. If a straight-line approximation to the black-body curve were adequate, you could get away with only two light sources.

Yes, I am guessing that two fairly spectrally smooth tubes would do. One "warm", one "cold" as long as they could be lineary mixed to produce fairly accurate intermediate color temperatures. If the flash is limited by total heat or total delivered power anyways this might not even be so inefficient as one might initially believe (two tubes and two power delivery circuits though).

Is it at all realistic to automatically control color temperature? Did not Nikon use to have a separate ambient WB sensor on their cameras? Put one on this flash and estimate ambient WB right before firing the flash. Might not be perfect for mixed-lighting, but might be good enough for 80% of the shots...

-h

[hjulenissen]

Pssst... patent it before someone else does

I guess this post counts as "prior art". As long as I can buy the product, I am happy :-)

-h

[theguywitha645d]

I wonder why flash tubes are daylight? Perhaps it is difficult to vary the spectral output? Then to build in either a color meter or to get the camera WB information would seem very complex.

To be honest, how difficult is it to carry a few color compensating filters to stick onto a flash unit?

[xpatUSA]

I wonder why flash tubes are daylight? Perhaps it is difficult to vary the spectral output?

It's to do with energy levels. The electrons in the gas get excited by the high voltage from the flash-gun capacitor and jump into different orbits around the atom nucleus. After the voltage is taken away, they jump back to where they came from but they have to lose energy to do that. Energy is emitted as photons, the stuff of light. Stop yawning! The thing is, the energy per photon is dictated by the material, in this case - Xenon gas. The said energy dictates the photon's vibration frequency i.e. it's wavelength, therefore it's color.

 Apparently Xenon has many different possible levels for it's electrons when excited, so the photons emitted may well have many different frequencies - hence "white light". Or maybe it only has three, but they just happen to be R,G and B in equal luminance. I'm sure someone knows . . . actually, a xenon spectrum would tell the tale if anybody has one.

That being said, the material dictates the color. So the color can not be changed without changing the material. For some materials, doping during manufacture can change the color, but not on the fly.

Ted

[David McCaughan]

I can buy a lot of gels for what this is gonna cost. 

[xpatUSA]

. . . actually, a xenon spectrum would tell the tale if anybody has one.

That being said, the material dictates the color. So the color can not be changed without changing the material. For some materials, doping during manufacture can change the color, but not on the fly.

Here y'are:



Lots more here: http://en.wikipedia.org/wiki/Flashtube

[jvb]

Nice idea. The old color enlarger technique jumps to my mind. A Dichromatic filter that can be dialed in gradually?
Must be possible to couple it with the WB of the camera.
Anyhow, not really a DIY thinkpath, but something for the "Toyotas" .

johan
www.vanbecelaere.com

[hjulenissen]

Seems that someone had a similar idea:
http://www.kickstarter.com/projects/508804913/the-rainbow-flash-wizard