While reading recent posts on layout lighting, I found that there is some confusion about white and color temperature. This is not the forum for Color Theory, or a thorough evaluation of Dr. Kelvin. Just the facts.
My background is Film, Photo and Video, so White White is important.
When our Club bought our building, it had the generic Fluorescent work lights on the 15 foot ceiling. Looks white so far. But if you open the garage doors, some of the walls seemed to change color. When the dining area was added, the 65 watt tungsten bulbs added another color flavor. We went next door to see what the machine shop next door was doing. They had replaced the overhead lights with High Intensity sodium vapor lights, Nice and bright, but still another color shift.
Heres what we have. Color temperature is a comparative measure of light output against a fixed standard. A Dr. Kelvin figured out a scale to deal with the numbers. Think of Fahrenheit and Celsius. Now we add Kelvin (K).
When discussing how hot something is, we associate color, because that's actually a fair indicator. In steel mills you will see RED HOT steel. If it gets REALLY hot, we get to WHITE hot.
Regular tungsten bulbs are in the area of 27,000 to 30,000 K. (Thats Kelvin, not Kilo) Halogen bulbs are tungsten bulbs designed to burn hotter, so they show up around 30 to 33K (note the abbreviation). Daylight shows up around 50 to 60 K, depending on weather etc. Daylight is lit by the Sun, higher output temperature.
So heres the difference. Regular (Tungsten ) bulbs are close to the red hot of molten steel, so they're producing a reddish version of white light. Sunlight is closer to that white hot end of the scale so its producing a bluish version of white. How do you see the difference? You could take a picture. If you are in a large white room that has tungsten lighting and a small area is lit by sunlight through a window, you will see a color shift where the two sources combine. Now pull out your digital still or video camera. It has auto white balance. It sees what your pointing at and figures that the bright stuff it sees is white, so it adjusts itself accordingly. So in the example of our train club, I'm sitting in the dining area, lit by regular bulbs, and in the background is the rest of the white room lit by the florescents, and the garage door is open so part of the wall has daylight. I take a picture and my friend, sitting in front of me in the white dining are, reading a printout from the computer, looks absolutely normal and holding white paper.
But the sunlit wall looks blue. Whats worse, the rest of thee building looks green.
Now imagine your Santa Fe Warbonnet or your SP Daylight circling the layout. How many color changes is it going through?
Thats the quick example of color temperature of your lighting.
How do you fix it?
The first question is "Do you care?" If you dont understand or see the problem, you might as well stop reading here.
Now heres how we fixed the problem at the club.
First, get rid of the white walls, color shift is easiest to see on white. Our walls have a photo backdrop and are painted a medium blue to the 15 foot ceiling.
Next, realize that you do not want fluorescent cool white, which is GREEN, or high intensity Sodium which is Orange, or Mercury Vapor, which is also Green. These have high light output but are missing significant portions of the color spectrum. Your Daylight might look reasonable but your Warbonnet wont.
What I did is as a first stage, installed tungsten flood lights about 10 feet high to light the area. Then changed the 8 foot tubes on the ceiling to color corrected, tungsten balanced tubes, Menards or Home Depot, etc. Now I have a well lit layout area that has a consistent color. We covered over the windows and door glass to keep the blue light out.
This summer we are advancing the project by installing track lighting (The overhead stuff) to properly illuminate the layout we will be building next summer. The track is placed over the aisle ways so it will shine over you to the layout in front of you, not into your eyes. It will be hanging down 5 feet from the ceiling so it will be about 3 feet over your head, which will provide a nice lighting angle of about 45 degrees. The lights will be WARM WHITE DIMMABLE LED's.
This combination of lights most closely complements your home lighting, the interior lighting you are most used too.
Now a quick rundown on light colors
Tungsten, regular bulbs, are the reddish light we know and love. They have a reasonably full spectrum so show color well. The equivalent of WARM WHITE in other bulbs. Fluorescent bulbs are typically COOL WHITE, have a limited spectrum, and are greenish. The other end is Daylight Which actually has a fantastic spectrum, but is hard to control. One of the reasons NOT to have skylights in your train room if your serious about your scenery.
I will now be deluged with a bunch of YEA BUT's but thats the basics, and the reason for setting up your train room in Tungsten Lighting, whatever the source.
