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I would like a recommendation on choosing which light-bulb type (e.g. CFL) and color temperature is best for prolonged computer usage.

I am also in a field where color consistency is important so if a specific lamp temperature is useful, I would like to know as well.

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Edited title: Most of the time, past participle should be used when using it as an adjective or adverb. Prolonged use not pro-long use. e.g.: painted house not paint house to denote a house that has been painted; three-legged man not three-leg man; fried rice not fry rice to denote rice that has been fried. –  Blessed Geek Mar 25 '11 at 2:05

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According to this article you should work under lights with a high (bluer) colour temperature.

Research has shown that working under light with a high color temperature has a number of benefits. Higher color temperatures are correlated with activated mental acuity (study of 7500K versus 3000K), reduced drowsiness (study of 5000K versus 3000K), and improved concentration and thought clarity (study of 17000K versus 4000K).

“Color temperature” refers to the color of the light produced; bluer lights increase productivity and alertness while yellower lights promote relaxation.

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OTTLITE

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I have three of these lamps around the house, they are fantastic. Their bulb technology offers the full light spectrum as seen in natural daylight.

It's great for the eyes without seeming harsh and even makes reading very comfortable.

http://www.ottlite.com/

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The OttLite looks exactly like a flourescent bulb that is daylight color balanced (i.e. ~6500K color temperature). You can get alternatives elsewhere and they are just as energy efficient. –  Berin Loritsch Mar 25 '11 at 12:43
    
I have one of these, and it's much nicer than my previous solution ("daylight" bulb in a standard desk light). The daylight bulb was only 60W, but it was much too bright for a desk light. If any of the local stores carried these in a 40W, I'd probably give them a try. I got the OttLite at a closeout, but ISTR that it was a little spendy at the regular price. Came with a spare bulb, though, and I love the styling. –  TMN Mar 25 '11 at 13:04
    
@Berin Loritsch - Sorry but I've tried 'alternatives', they are inferior to ottlite... ottlite does not make your eyes hurt as someone stated before (flickering that you can get with some bulbs). Like I said I've tried all alternatives before settling on Ottlite - its the best desk lamp in my opinion. Go borrow an ottlite, and some generic 6500k bulb from the shelf and then come back to me :) –  Dal Mar 25 '11 at 14:23
    
See my answer for further explanation of what it is about the ottlite that you like. Basically, it boils down to color temperature and contrast. It's a comparatively low contrast light source, which avoids the problems of hot spots. A little diffuser material (like white acetate) and you've got a similar effect. –  Berin Loritsch Mar 25 '11 at 14:42
    
@TMN, The key is the fluorescent bulb. A "daylight" balanced tungsten light (standard bulb) still has the hot-spot problems you've experienced. The larger fluorescent bulbs have a lot less contrast to them. One of sufficient quality will also avoid the flickering commonly associated with those lights. –  Berin Loritsch Mar 25 '11 at 14:44

From my photography experience, there are three aspects of light to consider for any scene--your office included. They are:

  • Quantity -- how much light there is (measured in lumens or lux)
  • Quality -- how direct or diffuse the light is
  • Color -- the color balance (measured in degrees Kelvin)

With photography, there's two standard color balances to be concerned with: tungsten balance and daylight balance. Tungsten is around 3400K, give or take a bit. Daylight is around 6500K. Based on the research other answers pointed to, you really want daylight balanced lighting.

That leaves the other two aspects to consider. How much light you need, and how it shines in the scene. I can use these to explain why the halogen is bad. Halogens are very high brightness, with a pin point source. That means your shadows are going to be really hard and your reflections really sharp. That's bad for prolonged use because your eyes will get fatigued dealing with the sharp contrasts.

  • You want a larger light source to reduce contrast and provide a more even light. Both LED lighting and fluorescent lighting provide this, but the effect of a larger light can also be done using some sort of diffuser. A white acetate on the top and bottom of your lamp gives the effect of a larger light source than originally exists.
  • You want enough light so that your eyes can focus for long periods, but not so much that it causes problems seeing the screen. A dark room is only effective if you don't have to reference printed materials. You want just enough light so that it is comfortable reading the printed materials, but not much more than that. Too much light and you have to squint to limit it. That's why it's such a pain to read outside.
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Most modern CFLs give pretty much white light, the difference with incandescent is that CFLs' spectrum isn't continuous. Also the flickering problem early models had is now completely eliminated. So it's good enough to light the room you're working it.

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White is relative. Given no other source, even a candle would be considered "white" to our eyes (color of a candle is ~1000K). Tungsten balance (3400K) is commonly considered white because all the lights in the house are the same. However, when the sun comes through the window (~6500K at mid-day and up to 9000K in the evening) you can see just how yellow the incandescent bulbs and tungsten balanced CFLs really are. NOTE: I agree that they have fixed the color problems with CFLs now. (No green spikes in the spectrum) –  Berin Loritsch Mar 25 '11 at 13:00

There's a lot of variety in what people like. I prefer a yellowish to white light over the blue ones. However, for locations where incandescent and halogen don't work, I'll take the white-blue of an LED. I strongly dislike fluorescents of every variety, full-tube, CFL, doesn't matter they all give me headaches after extended use (I will use CFL to save energy in non-work locations though, as the CFL headache issue only happens when used with a computer screen).

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Avoid halogen (EDIT: meant to say Fluorescent)... they'll give you a headache after a while. I always prefer the ones that attempt to produce natural light over the ones that give off that yellowish hue. Also if you have a way of reducing the light in the room as well as the brightness of your monitor (both to a comfortable level compared to each other) do so as less light for long periods of time is easier on your eyes. Someone once suggested to me that turning the lights off and adjusting the brightness on your monitor WAY down was best but I have never tried it myself.

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On the halogen... You don't really notice it but it causes the light in the room to pulse which is what causes the headaches... –  Kenneth Mar 25 '11 at 3:12
    
I'm sorry, but that doesn't make any sense to me. I've worked with lighting and optics. Halogen is a form of tungsten lamp, which works by heating up to the point of glowing. They give off a consistent brightness that does not pulse. Flourescent lamps, on the other hand, use a coating that turns a form of radiation directly into visible light. This light pulses at the regular 50 or 60 Hz of your electrical grid. The effect is plainly visible if you use a shutter speed significantly faster than 1/50 or 1/60 of a second. –  Scott Whitlock Mar 25 '11 at 11:49
    
I must have confused the two. I'll make an edit. –  Kenneth Mar 25 '11 at 14:33

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