Up for air

I thought I’d give a little update on the progress we are making. I’ve been heads down in development to the exclusion of almost everything else since the decision was made to change the form factor of the light. We’re now literally seeing the light at the end of the tunnel.

This is going to be a bit geeky, sorry bout that…

Color Temperature

We have a working color temperature range from 1850 to 15000 now.  The low end, 1850, is about the color temperature of candle light and that’s pretty nice. You can adjust the color temperature over the whole range without affecting the brightness of the light. It is technically possible to extend below 1850 but expensive in terms of power.  Expensive because the power is constant over the entire color temperature range and the red emitters max out at low CT. We have to lower the overall light output as we extend the minimum color temperature downwards. 1850 looks like a reasonable compromise.

An alternative would be to decrease the light output as the color temperature decreases. But that would mean that if you change the color temperature, you will have to change your exposure as well. It makes it more messy and increases the chance of error. I don’t like that.

Another nice thing is that you can add filters with no loss of power. You might prefer to stick the light on a Daylight setting and add filters instead of adjusting color temperature directly. If you put a 1/1 CTO* gel on your traditional light you lose 1.1 f-stop. With the light we are developing you lose nothing. Put on any correction filter you like, the light output and your exposure is the same.

How does that work? It works because the microprocessor in the light keeps the output constant regardless of color temperature. If you have the light set to, say, Daylight, then adding a 1/1 CTO filter is exactly the same as changing the color temperature from Daylight (5500 Kelvin) down to ~Tungsten (2900 Kelvin).  Just to be clear: This light uses electronic filters not physical gels. A physical filter works by selectively blocking parts of the light. A filter that cost you 1.1 f-stop, would block a bit more that half the light. Probably 55% or so of the light is lost (1 stop = half the light). What we do instead is simply adjusting the entire spectrum to produce a light of the desired color temperature. Cool, yes?

I’m back next week with more.

 

Cheers,

M

* CTO = Color Temperature Orange. A color correction filter used to “warm up” or decrease the color temperature of a light source.

 

2 Responses to “Up for air”

  1. Interesting question!

    I don’t know what the average transmittance characteristics are for the Bayer filters in the various cameras. The question certainly triggers my inner nerd 🙂 I assume those specs are available for many sensors. Don’t know if the big camera manufacturers have their own versions.

    It is not possible (or practical) to pick LEDs to match human response exactly, so we measure the color coordinates of the LEDs and do a color matrix transformation. The base color representation in the device is CIE 1931 xyY.

  2. Hi, what LEDs are you using? Did you choose the peak wavelength according LMS cone response or average digital camera qe peaks?
    What is the light-output of the complete array?

    Thx,
    Christian

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