Using AC with LEDs (Part 4) - The New Technologies

Step 4 The light

I took this uncorrected composite with the white-balance set to "daylight". On the left is with a 50-watt halogen, and on the right, what it looks like with our 3-watt LED "bulb". The last picture is the same view with the LED light on the left.

Although seemingly very blue, the LED light's spectrum is almost identical to noon-day sunlight, and is what our eyes see best with. As an experiment, cover half of the picture with a piece of paper and see how fast your eyes adjust to the different light spectrum.

Comments

[blazingpencilsdotcom]

Confused about the photos here in step 4, the description in both composite photos is the same so they contradict each other. I assume the bluish side is the LED's, and am looking for warm-light LED solutions and variable color-temperature solutions with mixing/dimming. Got suggestions? Thanks!

[qs]

The 'blue' half is indeed the LED output, although its spectrum is almost identical to outdoor noonday light.

As volto said, white light can be approximated by a mix of red, blue and green, but that solution is limited because the yellow is produced by adding a bit of green to red and doesn't really remove the 'glare-y' feel,

Another approach is to use a 'warm' white LED, which has more yellow phosphor. Although somewhat warmer feeling it's also less efficient.

[volto]

For natural light you could use equal parts Red Green and Blue leds, although the lumens per watt will suffer slightly.

[qs]

It's kinda ironic: the human eye is most sensitive in the blue spectrum, we 'see' it more, and that translates to glare. And since lumen measurement is based on the range and sensitivity of our vision, doesn't that mean that, by definition, only low lumen-per-watt lights can feel warm?