A typical halogen bulb only puts out 21% more lumens than a typical incandescent bulb, although this can go up to 40% for certain high power types of halogen bulbs.
Originally Posted by Not Amused
Well, part of the reason for this (more vissible light per watt) is simply that the human eye is more sensitive to yellow-green light than red light. When the color distribution gets shifted more towards the blue side of the spectrum, a higher ratio of the light is yellow, green, and blue. In other words, the lumen rating is being increased by shifting the light color. For incandescent lights, this is usually a good thing, since normal filaments tend to be a little orange-yellowish and halogen gives a whiter light. But some people prefer the oranger "softer" color of light, and it may also be more desirable for certain places where a "cozy" feel is desired. While halogen filaments are a little more efficient at producing orange-red light, most of their "efficiency" comes from producing more of other colors of light. This is why it is not always really fair to use the lumen ratings when discussing efficiency. The most "efficient" light possible, for example, would produce all green-colored light. Indeed, many manufacturers of fluorescent lights actually "cheat" by incorporating more green phosphor to give the tube a higher lumen rating, but this results in an ugly greenish tinge to the light.
And the "warm white" LED's are deficient in far red frequency light, not because red phosphors do not exist, but because incorporating more of this light would lower the lumen rating because the human eye is not as sensitive to it as orange-red light. But the absence of this far red light decreases the LED's CRI index, certain red colored objects are not illuminated as well, and the color rendering seems more "off". The latest high-CRI technology LED's incorporate a separate red LED chip, because it is more efficient to directly produce this light than to produce it through a phosphor. But this adds complexity and expense. The 10 Watt Phillips L Prize LED light, incorporates this far-red color light, but is currently being sold for 50 US dollars each.
Although the Phillips L prize has a has a better spectrum distribution than normal white LED's, it is still far from perfect:
Apes and chimpanzees are dangerous animals. They might seem fuzzy and harmless one moment, but the next moment a whole pack of them can gang up on a human victim and viciously tear them to shreds.