I've been doing a little electrical engineering (outside of my lane a bit). I'm trying to get the RGB values for Edison light bulbs. Can anyone provide me with those?
Edison Light Bulbs RGB Value – What You Need to Know
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This is running on the assumption that you are using a supply of 5v.
For the resistor calculations you want to use Ohms law V = IR, where I is the current you want to flow through the LED and V is the voltage difference between what you are supplying and what the LED is specified for. The voltage you want to use is the typical voltage listed on the datasheet, so for the case of red you have (5v - 2.1v) = 20mA * R -> R = 2.9v/20mA = 145 Ohm. The green and blue channels are calculated similarly using a voltage of 3.8v and 2.7v respectively.
To understand the results you are getting you have to consider the spectral response curves of your light source, detector, and the object being measured. The final result is a combination of all these 'filters' acting on the signal. And if you want to relate that to the colors you see, then you also have to take into account the spectral response of the human eye.
I'm using a Photoshop print on a matte photo print paper as the color
A photographic print is calibrated to show correct colors when viewed by the human eye. This does not mean that it will reflect all the color components in direct proportion to the values in the digital image. The pigments or dyes used in color printers don't produce pure colors. A perfect 'green' ink (which is actually a combination of cyan and yellow) would reflect all wavelengths between 495 and 570nm ('green') while absorbing all other wavelengths in the visible spectrum ('blue' and 'red'). But practical inks do not have such sharp response, so 'green' ink won't reflect all green light, and may also have some blue and red in it.
To compensate for the color being too dark the printer may lay down less ink to let more of the white paper show through. But traces of blue and red in the 'green' could make it look muddy or washed out, which the printer may compensate for by adding black. The printer may also alter color ratios to get a more accurate hue. The end result looks alright, but is not an exact match to the digital RGB value of 0,255,0. What you are seeing is not actually pure green, but a mixture of many different colors that just look like pure green to the human eye.
Another factor to consider is the spectral output of your LEDs. Most green LEDs emit a fairly narrow band of green light, If this doesn't line up with the ink's spectral response then the output could be lower than expected. If you then calibrate to this lower value and call it '255', a pure white image could read higher than expected because the plain white paper reflects more wavelengths of green light than the 'green' ink does.
Finally, the detector's response could be distorting the results. Standard photo-transistors peak in the near infra-red, and response drops off rapidly towards the blue end of the spectrum. This could skew the response so that 'yellow' green produces a higher reading than 'blue' green.
Bottom line:- the printer modifies the image's RGB values to produce a result that looks right to the human eye, so to get a meaningful result your emitter/detector combination must replicate the spectral response of the human eye. Even then, the results won't exactly match the RGB color values in the digital image (1%? forget about it!).
Best Answer
I used Firefox Web Developer Eyedropper to grab the RGB from a photo of an Edison Light Bulb.
#FACA08
(250,202,8)
A lighter pixel
This is very close to the color when a 2700K 97 CRI LED was reflected off bright white paper: #F4D4AB (244,212,171) just a little less blue.
#F5D483
(245, 212, 131)
I do not believe the LED actually illuminates using the color you see when viewing the filament. The filament LEDs are no different from other lighting LEDs. Many of these "Edison Lights" have Color Correlated Temperature (CCT, e.g. 3000K) and Color Rendering Index (CRI, e.g 80). With that you can get the CIE x,y chromaticity coordinates based on CCT and CRI. Both CCT and CRI are needed although CCT only will suffice. Once you have the x,y chromaticity coordinates they can be translated to RGB.
LED datasheets often have the CIE x,y chromaticity coordinates as shown here:
Using CIE x,y chromaticity coordinates from the datasheet of a 2700K CRI 90 LED (red x,y).
I wrote an SVG app to plot the x,y on a chromaticity diagram to compare two LEDs.
The red x,y are from a Citi CLU036-1205C1-273H5G3 2700K 90 CRI
The blue x,y are from a Citi CLU036-1205C1-30AL7G4 3000K 70 CRI
I used the eyedropper to grab the RGB off the chromaticity diagram for the 2700K 90 CRI.
#F7AF60
(244,175,90)
Using CIE x,y chromaticity coordinates from the datasheet of a 2700K CRI and using a CIE Color Calculator I get:
#FDAC5A
(253, 172, 90)
Some various CCT and CRI reflected off high grade bright white paper.
#F06F5C 1750K CRI 98
#E2CBAC 3000K CRI 80
#F4D4AB 2700K CRI 97 (244,212,171)
#E96C66 Luxeon Fresh Focus Red Meat
2700K is a very warm light. 97 CRI is very close to (natural) sunlight (CRI 100 = sunlight)
There is no difference between a "Edison Bulb" and any other LED light bulb.
In my opinion a nice warm light is 2700K with a high CRI.
Grabbing the RGB with the eyedropper from the reflection of a 2700K 97 CRI LED off a bright white paper we get this:
Not a very "golden glow"
2700K CRI 97
Measured with a StellarNet BLUE-Wave Spectrometer
The PPFD is a measurement of the number of visible photons in µmols.
So this PPFD measurement shows exactly what wavelengths are being emitted (as a plant "sees") before they are adjusted for photopic luminous efficacy (human perception).
2700K CRI 97 Quantum µmol/m²/s (number of photons)
Slightly lower CRI, more green and less red.
2700K CRI 90 Quantum µmol/m²/s
When the number of photons are adjusted for photopic luminous efficacy it is not what most people would expect. This is exactly the same LED being measured (seconds later) with the same spectrometer as the first image with the measurement units flipped from PPFD to Lux.
2700K CRI 97 Photometric Lux
Examples of Low and High CRI