# Simulating sunlight



## steve90 (Sep 26, 2010)

Hello all, I have decided to give your forum since you seem knowledgeable here about lighting. 

I would like to know if it is possible to use artificial lighting to mimic natural sunlight in a room with poor sun exposure. The room is a building where heliostats/outdoor reflectors would not be an option. 

While fluorescent lighting is bright while you look at it, a few bulbs does not provide the intensity to light up every corner of the room the way direct sunlight does. It also makes objects look white instead of giving it the warm glow as with natural sunlight and gives off a subtle flicker. Is this the best technology for this project or would LEDs and/or incandescents be better suited?

Does anyone have any suggestions on the type of lighting, type of bulb, color temperature, number and spacing of bulbs and fixtures or ballasts required to fill up a small room with artificial light that approximates natural daylight in a room with good sun exposure without blowing a fuse?

I was specifically wondering if a "virtual window" could be created on a wall using artificial lighting. 

Thanks for any suggestions.


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## Ken_McE (Sep 27, 2010)

steve90 said:


> I would like to know if it is possible to use artificial lighting to mimic natural sunlight in a room with poor sun exposure.



Yes.




> While fluorescent lighting is bright while you look at it, a few bulbs does not provide the intensity to light up every corner of the room the way direct sunlight does.


That's not the goal of normal room lighting.




> It also makes objects look white instead of giving it the warm glow as with natural sunlight


You might be used to cool white fluorescent bulbs. They come in warmer colors too.



> and gives off a subtle flicker.


A newer ballast or bulb might eliminate that. The older fixtures with the magnetic ballast tended to flicker.



> Is this the best technology for this project or would LEDs and/or incandescents be better suited?


I think you should check the the light output from a fully modern T-8 or T-5 fluorescent fixture with electronic ballast and warm white bulbs - maybe light up a closet or something- and see how you feel about the quality of the light. Your project is perfectly doable but will require a little research.



> Does anyone have any suggestions on the type of lighting, type of bulb, color temperature, number and spacing of bulbs and fixtures or ballasts required to fill up a small room with artificial light that approximates natural daylight in a room with good sun exposure without blowing a fuse?


Comments on some light sources as relates to your project:

*Incan* bulbs will give you something quite similar to natural daylight. Their flaws are that they are inefficient, short lived, and produce a lot of heat.

*Fluorescent* are long lived and efficient, but you will have to mix and match to get a spectrum you like. Skip the little CFLs and use the four-foot tube types.

*LED* is efficient, but they are all expensive and very narrow band. I think you should give them a pass here.

*HID* (various types) are great for sheer raw power, but they all have light that is tinted or slanted differently than natural lighting.



> I was specifically wondering if a "virtual window" could be created on a wall using artificial lighting.


Yes, you might start by building one just to test different light fixture mixes.

Here's a suggestion for how you might start:

Go buy a 4-bulb 4' Fluorescent light fixture with a T-8 ballast. Get sets of T-8 bulbs for it in cool white, warm white, and plant grow bulbs. Set it up in a closet or bathroom or something and try spending time with it with the different bulbs in it. See how you like the different lights. After you're familiar them try mixes. I'd suggest two warm whites, one cool white and one grow bulb. See if there's something you feel good spending time in.


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## LEDninja (Sep 28, 2010)

You can look at lighting designed to treat seasonal affective disorder. Some are too blue so make sure you get Natural Spectrum lighting versions.
They are very expensive though, especially if you want to light up a whole room instead of just a small work area.
See Light therapy in wikipedia
http://en.wikipedia.org/wiki/SAD_light

Sunlight is considered to have a colour temperature of _~4500°K_***. This actually varies depending on time of day, time of year, latitude etc.
*** OOPS
Cool White (ANSI): 5000K-8300K
Neutral White (ANSI): 3700K-5000K
Warm White (ANSI): 2600K-3700K
There are a number of LED torches out with neutral (sometimes labeled warm) tint. You can check out the colour if not the brightness with them.

I have success getting a much more comfortable light just using a cool white CFL and a warm white CFL in my small apartment kitchen than with either type alone. Both 23W - 100W incan equivalent. Still nowhere as bright as direct sunlight.


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## steve90 (Oct 5, 2010)

Thanks for your suggestions. I was on that path myself with regards to the 4' T8 bulb panel. This would simply be an enlarged scale of the S.A.D. light box I have.

However, it is annoying to have the SAD light on the side of my desk when I am trying to look at the computer screen. I close the blinds when there is direct sunlight coming in around noon.

Then maybe a "virtual window" of fluorescent bulbs that I would cover up does not make sense for a home office. Maybe I should light the room traditionally from the ceiling downward or have light pointed upward and diffused such as by a halogen floor lamp.


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## Ken_McE (Oct 6, 2010)

Some other things to consider:

Paint the entire room high gloss white. This will help brighten it up with anything else you do. If this is not acceptable, look for light shades of whatever colors you prefer.

You could get one or two 200~300 watt Metal Halide HID lights and use them as wall washers or torchieres at either end of the room. I find the light a touch greenish but it would certainly pump up the overall brightness.

You could make a plant tray with a line of grow lights running along the top of it. Bring in a little of the outdoors to light up your life. Maybe run a mirror along in back of it like they do in supermarkets.

_
Then maybe a "virtual window" of fluorescent bulbs that I would cover up does not make sense for a home office._

Just put it where it is not directly in your eyes or on the screen.



_Maybe I should light the room traditionally from the ceiling downward or have light pointed upward and diffused such as by a halogen floor lamp._

You could do both. After all, you are after a lot of light


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