A LED light a little closer to adjustable full-spectrum

[enricosavazzi]

Prolycht introduced a studio LED light a little closer to adjustable full-spectrum (VIS only) than RGB LEDs. This new light uses LEDs emitting at 6 wavelengths instead of 3:

 

http://www.prolycht.com/orion300fs/index.aspx

 

There has been some previous discussion on UVP of possible full-spectrum LED sources (the way we usually intend it here, i.e. NUV + VIS + NIR) using multiple types of emitters, and/or of multi-wavelength LED sources of NUV built on a similar principle. The main problem with the latter is that UV emitters at wavelengths shorter than 365 nm are still much more expensive and much less efficient than the now relatively commonplace 365 nm power LEDs, but things are - slowly - changing.

[colinbm]

Interesting.
It is unfortunate that they describe this a 'Full Spectrum' when in fact it is 6 wavelengths in the visible spectrum.
The cameras still only see RGB & interpolate the rest, I guess this will still happen ?
I am now finding a good range of LEDs from 255nm through to 400nm are now available, but not without their drawbacks.
I have now individual lights from 222nm Excimer UVC, UVC mercury vapour fluorescent & LEDs 255nm, 265nm, 275nm, 295nm, 310nm, 340nm & 365nm.
They all leak in the Visible, which I am now gathering filters to block this Visible light leak.
Hopefully in a month I can give a demo on UV A, B & C fluorescence.
 

[Stefano]

10 hours ago, colinbm said:

The cameras still only see RGB & interpolate the rest, I guess this will still happen ?

Not quite, you have additional information from 6 LEDs because the channels in a camera overlap and this makes it sensitive to all wavelengths in the visible spectrum without gaps (like our eyes).

 

An object that reflects only "pure" yellow light (not red+green, but something like 570-590 nm) would appear dark under a normal RGB LED because LEDs are quite monochromatic and there would be little actual yellow light emitted. Under a yellow LED, it would look bright.

 

If the RGB channels in a camera were completely distinct and with gaps, then yes, a camera wouldn't see much difference. Since they overlap, you can get a yellow signal both from red+green and yellow.

[colinbm]

Thanks Stefano

[DKoch]

On 3/19/2022 at 8:25 AM, Stefano said:

Not quite, you have additional information from 6 LEDs because the channels in a camera overlap and this makes it sensitive to all wavelengths in the visible spectrum without gaps (like our eyes).

 

An object that reflects only "pure" yellow light (not red+green, but something like 570-590 nm) would appear dark under a normal RGB LED because LEDs are quite monochromatic and there would be little actual yellow light emitted. Under a yellow LED, it would look bright.

 

If the RGB channels in a camera were completely distinct and with gaps, then yes, a camera wouldn't see much difference. Since they overlap, you can get a yellow signal both from red+green and yellow.

The problem I have in my work (cinematography) is that the spectral response curves of the RGB Bayer filters in the sensors are all different! We use a LOT of RGBWW ( RGB White (5600K), White(3200K) etc now . They have quite good rendering.I have always wanted to add 410 and 390(?) nm LEDs to strengthen the short wavelength end. In one of my applications I'll be building my own fixture that will be White and  365  & 390 nm sources...

[colinbm]

"I have always wanted to add 410 and 390(?) nm LEDs to strengthen the short wavelength end. In one of my applications I'll be building my own fixture that will be White and  365  & 390 nm sources..."
But monitors don't display below blue 420nm.
Below 420nm the full spectrum camera will start to record the UV false colours.