• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Lighting Design

peach

Registered User
Joined
Oct 17, 2009
Messages
2,834
Location
metro DC
In preparation for many things, including becoming a QA/QC inspector in the event the IgCC is really rolled out and implemented, a couple of things (well, mostly one) really puzzles me.... the Color Temperature thing.

We see it all the time on light bulb boxes (my CF bulbs are 2700 K bulbs).

I fell into an older lighting fundamentals handbook which actually explains how they come up with the Kelvin scale (and it seems complicated and stupid to me.. a scale of 1-10 seems easier).

the "K" number comes from the color of a comparable blackbody radiator being raised from absolute zero (0 Kelvin or -460 F) to, let's say, 2700 Kelvin (which I guess would be 2240 F). The "blackbody radiator" is black iron; since I don't remember my metallury so well, I'd actually assume black iron is going to melt at/before 2240 before it becomes the color of "soft white".

Lighting calculations require us to use the 2700 number..

anybody else think this is dumb?
 
Preach

When iron or steel is heated in a forge it goes through the color changes in the book. Buy it doesn't melt as it does in a crucible. It becomes 'plastic'. that is where the smith uses the hammer and anvil to form it into useful items.
 
peach said:
Lighting calculations require us to use the 2700 number.. anybody else think this is dumb?
It's not dumb. 2700K is approximately the output one gets from a common incandescent fixture.
 
pyrguy said:
PreachWhen iron or steel is heated in a forge it goes through the color changes in the book. Buy it doesn't melt as it does in a crucible. It becomes 'plastic'. that is where the smith uses the hammer and anvil to form it into useful items.
Calling him Preach. That typo made me laugh...

My $.02 worth. I bought some LED's. The 6000K were a horrible blue. Worse than floursecent tubes.

I got some 3000K and they are much better.

Get two bulbs with drastic differences in K light temp. and put them in the same room.. It will make more sense then.
 
Man 2700K is approximately the output one gets from a common incandescent fixture...So,this is not dumb....You should have two bulbs with drastic differences in K light temp in the same room.
 
"Calling him Preach. That typo made me laugh..."

That made me laugh.......peach is of the female persuasion. Surprised nobody else commented before me. :D
 
I wonder if there are any accesibility issues related to light sensitivity. I have worked with several people now who, and I am only guessing, suffered migraines when the T5 (or 8) bulb temp was over 3500K (might have had to do in part with computer eye strain). Most office design specs I see call for a range of 5000K to 7000K. That is not what I would call a lighting design, but rather de-industry's de-fault...and anybody who specs that should be blamed.
 
The K in lighting is the color of the visible light that the lamp produces. I like to use the black smith example to illustrate what the number means. If steel is heated to 2700 F, it has an amber glow similar to the color of an incandescent lamp. When steel is 3000 - 3500 F, it is white and so is a light with that 3000- 3500 K rating. Steel heated to 4000 or hotter turn blue. So lights with a 4000k appear blue. The standard office lights are 3000 - 3500K. So, to help read the labels on the lamps, if a light has T8 835, it would be T (tubular), 1" (every 1 = 1/8" just like rebar) 8 (cri or 80% of the visible light spectrum) and yes finally, 35 (3500K, so the light is white). Let me know if you need me to email you some good examples.
 
Top