I recently bought this white LED reading lamp. I like it a lot, but the "white" light produced is significantly blue; I'll guess its color temperature is about 5000K.

I've noticed that, when this is the only source of light, printed text appears slightly fuzzy, and is more difficult to read than with a standard incandescent reading lamp. My guess is that this is chromatic aberration causing color fringing in my eyes, making it harder to read with this new lamp.

Is there a way to make this lamp less blue using some sort of transparent/translucent filter over the lens? This could filter out some of the blue end of the spectrum, or include a phosphor to convert some of the blue to yellow (as most "white" LEDs do). The fluorescence idea would be better, as there'd be less light lost. I don't want to go too far, though; a strongly yellow lamp might be worse for reading than this currently blueish lamp.

  • If you were truly suffering from chromatic aberration, then what you would need is a monochromatic light source to read by, not a different color temperature. Also, incandescent light would make the problem worse, not better. There are a myriad of LED light sources that vary tremendously in quality. Some flicker quite badly and some have horrible CRI's that are annoying. You probably have one that flickers enough to bother your reading. – user39367 Oct 4 '15 at 17:06
  • No, there's no perceivable flicker, even if I try panning my eyes past the light. However, with a high color temperature "white" LED, there can be two sharp peaks, one in the blue, and one in the red, that exacerbate chromatic aberration. See electronics.stackexchange.com/questions/125500/… – Daniel Griscom Oct 4 '15 at 17:34
  • The way to change the color of an LED lamp is to change out the LED. Filtering for narrow spectrum light sources merely filters out the light. Also, the bluer LEDs often have UV output that causes issues. You need to start with a proper light source which would be probably 4300K or warmer White LED with a phosphor mix that gives a good CRI (broader spectrum white light). White LEDs work by converting ultraviolet (like common fluorescent lighting) to white light with phospor powder embedded in the plastic lens housing. – Fiasco Labs Oct 4 '15 at 17:36
  • I believe these days most "white" LEDs are blue LEDs plus yellow phosphors; see lighting.philips.com/pwc_li/main/connect/Lighting_University/… – Daniel Griscom Oct 4 '15 at 18:02
  • @FiascoLabs No. LEDs do not emit UV light at all - unless you pay through the nose for LEDs specifically made to emit UV, which requires special and expensive doping in the LED junction proper. Long wavelengths are easy, short wavelengths are hard, and LEDs don't go any shorter than they absolutely have to, which makes them ideal for archival lighting. You're thinking of fluorescent - THOSE start with UV. – Harper - Reinstate Monica Jun 19 '16 at 2:41

Chromatic aberration interfering with reading would be a very unusual complaint (so says an ophthalmologist I know). On the other hand, cataracts do block and scatter blue light more than the lower end of the visible spectrum. So, if one has cataracts then it can be harder to read under blue light. Most "white" LEDs use a monochromatic blue source (not UV), which is then fluoresced to the lower frequencies with phosphor. Good phosphor is expensive, and more fluorescing hurts efficiency. Consequently, cheap LED sources tend to be blue and have a poor CRI. Practically speaking, an LED with poor spectral characteristics cannot be improved once manufactured. You need a different lamp.

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  • There's a very real possibility that my only recourse would be a different lamp. Unfortunately, this is the only lamp I've found that meets my other constraints (dimmable, large and positionable emission area, wall-powered). – Daniel Griscom Oct 4 '15 at 18:03

On a small scale, I have had "decent" (not perfectly warm but MUCH better) luck using Brown Spray Paint on low voltage LED's to change the tone, even though they were in the warmer color spectrum. Have lasted and no ill effects to bulb life to date.

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I'd try to correct this with cinematic gels - sheets of tinted plastic used to correct cinematic lighting. You don't need to buy a variety - you can stack up multiple layers.

It may just be too darn bright. After 40 years of seeing tiny red LED indicators, one thinks LEDs struggle to make a paltry amount of light. Not at all. They can be extremely bright because 100% of their energy is made into visible light in the desired cone - none wasted on IR light you can't see, or lighting up reflectors.

If the bulbs are replaceable, just go out and get the color temperature and CRI you want. Selection has gotten notably better even in the past year.

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