I plan to replace a CFL lighting fixture in a small room (10' x 15'), due to its being too dim and giving less-than-perfect light.

I'd like to install something that would give me 3500K light with color rendering index (CRI) ≥ 85.

My options are seemingly halogen and LED. I'm OK with replacing the fixture, adding transformers, etc.

  • Halogen bulbs I encounter seem to have low power efficiency, below 20 lm/W (example). This means lots of heat, which I would rather avoid.
  • LED bulbs I encounter usually have CRI of 80 or worse (example), which I would rather improve on.

What am I missing?

UPDATE: A cheap and relatively nice solution I ended up with is having several CFLs with various color temperatures, from 2700 to 5000.

I understand that my "3500K" requirement was due to misunderstanding.

Update Feb 2020: By now, high-CRI LEDs are not hard to come by, for any reasonable color temperature. My current setup with 3200K and 5000K srtips with independent dimmers proved to reproduce colors in a way which is hard to tell from natural sunlight.

  • It seems to me, you might be missing a question? Are you trying to find a bulb with specific characteristics, or trying to find out why manufacturers don't make a bulb that meet you specific needs?
    – Tester101
    Dec 17, 2012 at 13:14
  • @Tester101: yes, my question is a bit vague. I suspected that I may be misunderstanding the area, and someone will tel me: "Look, these [classes of] lamps is an obvious example of what you must be using". Efficient halogen lamps, small-scale HID lamps, etc. Now I'm going to accept the most upvoted answer and ask about specific lamps separately.
    – 9000
    Dec 18, 2012 at 3:19

4 Answers 4


You're not missing anything. LEDs that have a high CRI is a relatively new market segment, so the selection is limited, and prices are high. LEDs use the same tricks as fluorescents to reach reasonable CRI levels-- multiple phosphors with different spectra excited by the lamp's primary EM emission. So the potential exists to equal or exceed the best fluorescents. Right now, the consumer LED market is focused on replacing lamps in non critical applications, and thus tend to be rather low color temperature and only modest CRI levels. This situation should improve in the future.

"High" CRI fluorescent tubes are available in color temperatures from 3000 to 6500K, with CRIs between 80 and 90, and at reasonable prices. Right now, this is probably still a good solution for many applications. If the performance of these lamps are not adequate, halogen lamps are the only reasonable alternative. LEDs are not quite there yet.


A quick check on Wikipedia suggests that below 5000K the Color rendering index is unreliable in the first place. Incandescent lamps have a color temperature of between 2700-3300K and a CRI of 100.


Colour rendering index (CRI) is on a scale 0-100. A halogen bulb will have a CRI of 100. LED bulbs generally have a CRI lower than this as this is an area manufacturers can reduce costs. Generally a CRI of 75-80 or more will be fine in the home, however anything less than this and the colour of objects may start to appear strange. Philips have recently introduced a master LED bulb range with a CRI of 90. The LEDIFY bulb available from leds4less have a CRI of 80-95 plus video showing side by side comparison with a traditional incandescent, halogen and energy saver versus a LED equivalent


3500K is perfect lights CCT as sun light morning. if to use in room, >85% CRI is Important. for 10' x 15' room, one 8w light is enough. Lumen output 800lm with 85Ra CRI.

How to check the CRI is high or not, you can see your hand in sun light, then light your hand with the led light. If the color is same, then CRI is high more than 80%. The sun light is 100% CRI.

Hope this can help you.

  • When I switch on a 4100K CFL in a darkened room, it looks a bit bluish. When I do this in a sunlit rum, the same lamp looks quite orange in comparison. I suppose sunlight is way higher K: Sun's surface is about 7000K. But CFLs with this index don't provide enough reds / yellows and look unnatural.
    – 9000
    Feb 8, 2014 at 5:33

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