warm white led yellow fringe

[sm_jamieson]

I now have 3 types of LED, all "warm white" - linear under cabinet lights, 5W with 5 discrete leds, and 5W COB leds. I have noticed they all produce a yellow fringe, which is especially visible when used to create a wall wash or uplighting. On the cabinet ones it is expressed as bands of yellow due to the layout - SWMBO tells me this is bad for washing up (!?). Is this a product of the "warm s**te" (that was a genuine typo - look at the keyboard !) production, and is it something that will improve ? Simon.

[ARW]

[Mike Clarke]

I've just got a couple of 3.7W LEDlite MR16's from TLC and they have a distinct yellow tint towards the edges of the beam.

[Andy Burns]

Given that many of them are blue LEDs that frequency shift some of the blue light down to yellow, which then mixes with the rest of the blue to look white, is it likely to be chromatic aberration from the lens separating the two colours out a little?

If you wear glasses, and look at the LEDs at an acute angle do you see a similar effect?

[Martin Brown]

It is a quirk of how the white LEDs are made which is essentially a powerful blue LED pumping a yellow borderline orange phosphor. The two emitters are at different peak wavelengths and slightly different depths from the optics and get projected as different sized disks.

I can't see there being any cost effective way to cure this.

[Adam Aglionby]

Remote phosphor, efficiency takes a hit but get rid of the `brown ring ` problem

[sm_jamieson]

Interesting. The yellow fringe does not bother me all that much, but it would appear that the generally available energy efficient replacements for incandescent bulbs still have some way to go. Simon.