New anti-reflective coating--.1% reflection at some angles

News of a new anti-reflective coating for possible use in future high-end LEDs.

News story here.

Quick dumb question...how can you tell if there's AR coating? I know people look at it and can tell, and even can tell if it's on the inside or outside. I look at my lights that supposedly have AR and others w/o, and don't see much difference (plus it doesn't help that they're different materials...one's sapphire, the other glass).

Thanks.

The easiest giveaway is that light reflected off the outer surface of the lens will have a distinct hue to it if they are coated. Blue, purple, or green would be the most common. The lenses on a semi-decent pair of binoculars will show this. Lenses that are coated several times ("multi-coated" or "fully multi-coated") with different compositions may not show a very distinct reflective hue at all because the different coatings work together to reduce the reflected light so much that the lens looks invisible when you look straight at it in a well lit room.

I find that with good multi-coated lenses the best way to check them is to stand under a light fixture and hold the lens level down around my waist while looking at the lens. The lenses with the best coatings will reflect back almost no image of the turned on light fixture above your head.

I've seen a kid smudge the UCL lens on a mag mod because he thought there was no lens installed when he went to poke the bulb. He couldn't see the lens because it was cleaned of all dust motes and it wasn't reflecting any of the ambient room light back towards his eyes.

If you have a small shard of plain old regular flat window glass kicking around you could hold it beside a lens you want to check and compare the two, side by side.

I think most of you lights with AR coating has it on the inside, only a few has it on both sides (the CR2 Ion has it on both sides). The side facing the environment is much more likely to be scratched and damage the AR coating so most AR coted lenses only have it on one side. the other side appears like normal glass

Edit: Lumenhound explaned it better the me.