I have just shared a new project: “Salvaged Street Light Conversion”
IntroductionI salvaged some decommissioned street lights from the local transfer station. I suspect they adorned the main street of Woodend in the past and would now look good in our garden. They were banged up but mainly intact.
So I straigh…
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Hi @MarkMakies
Very neat conversion.
As a lighting engineer, and as a theatre lighting designer, I think that your partners ‘guidance’ re the designed appearance of the illumination is a great choice.
I must admit I also like the warmer colour temperatures in my household lighting - the current fashion for ‘sharp, white light’ is an uncomfortable choice for the living environment.
FYI here is a basic colour temperature chart for reference.
High Pressure sodium lights operate at about 2700K with a colour rendering index of about 85 (out of 100)
Low pressure sodium lights operate at about 1700K, and being monochromatic, have a colour rendering index of 0.
Cheers
Murray
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Hi Murray,
Thanks for the feedback. I never looked into the colour rendering index or knew much about it until now. I suspect that the CRI obtained from the GlowBits is pretty low given RGB values are 255,139,21 and the fact that the LED’s have a kind of discrete emission output.
Even though my Nikon SLR shows a similar colour temperature (reflected off a standard gray card) to the other commercial lights, it looks very red to me, especially indoors and in certain outdoor natural lighting conditions.
Can one easily measure CRI, or is specialist equipment required?
Cheers,
Mark
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Hi @MarkMakies
CRI is ‘interesting’ as it tries to represent how a coloured surface visually appears under a specific light source, when compared to the same surface viewed in ‘daylight’. Think of someone buying something, and asking if they can take it outside to look at it to ‘check the colour’. This was particularly prevalent in the early days of fluorescent lighting as they often had a nasty greenish tinge.
It was originally quite subjective, as there was no simple way of determining it empirically.
Now there are very specific measurement criteria and processes for it, but it can still be contentious.
Here are some useful links describing what it is, and how it is currently determined. And why it can be very important, i.e. hospitals etc.
And colour temperature is also interesting since technically it can only be applied to a black body radiator as it heats up. But by plotting the colour spectrum of a given source onto the CIE chromaticity diagram, and determining ‘how close’ it is to the black body line, an ‘equivalent colour temperature’ can be assigned to the source.
This is only an approximation, since most current sources do not have a continuous spectral output - there are gaps and peaks rather than a smooth, continuous output.
LEDs are in the ‘do not have a continuous spectral output’ category.
Here is the CIE chromaticity diagram, the black line is the black body temperature line. (the equal energy point is defined as ‘white’)
Hopefully not too much info (TL;DR)
Murray
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Hi @MarkMakies
Here is a simple visual image comparing light sources at various (simulated) colour temperatures
Murray
