Color Perception, a different twist?

I know there have been several posts in the past about colored leds and perception (or lack thereof) of viewing color, but I just noticed something this evening I thought I'd share with you.

The given information is that when using a colored led, you only see objects tinted that color, and black. Only white light renders true colors. This has always been my own opinion as well, in experience and what I know of visual perception. Weeellll...

I was using a blue LS in my home tonight, and wasn't at all thinking on this topic. I happened to notice, however, that in a totally dark living room, all objects were indeed shades of blue. EXCEPT for a few, small objects in bright colors like yellow, orange and some reds (I guess I don't have any big bright colored objects around). They stood out like a sore thumb, the way those black and white photos and tv ads do when they also contain one color object. It's very, very odd. I tried it over a variety of objects in many locations, and the brighter and bolder the yellow/orange, the more visible they are as themselves under the blue light. To make sure I wasn't mistaken (the old "you're seeing yellow only because you know the object is yellow), I tested it out on my wife, and she reported exactly the same thing. I also tried a cyan LS, and it worked similarly, but not as well. Those are the only colors that reacted this way, and they weren't flourescent. Maybe the blue and cyan LS also emit some white light? But if that were true, then you'd see all the colors, not just the bright ones. The phenomena is really kind of fun to see; try it out - total darkness, with one bright object somewhere in the room.

Another observation: I was comparing the two LS's, blue and cyan, against a white wall at close range (1ft) at the same time, with the room being dark. When I was looking at the light spots and making comparisons (as we all do), I clicked them both off at the same time. I was rewarded with a red (!) flash of "light" in my vision that lasted a few seconds even though there was no light in the room at all. Very odd again!

I am no longer of the opinion that there's only blue reflection from a blue led. I "know" there should be, but... there's the proof in front of my eyes (and my wife's, too) It's just so... darn obvious!

Phaserburn -

Blue and Royal Blue make fluorescent objects glow. I didn't know until recently when I was shining a cyan 5W in my living room that they will fluoresce objects also. I wouldn't have thought that would happen but it sure does.

Try pointing your blue at your watch. If it has any phospher it will charge up brighter and faster than with a standard flashlight.

Phaserburn-

I have noticed that my cyan light also shows up yellows and blue colors but I thought that this was due to yellow and blue components that make up the blue green light. By the way, have you tried to shine a white and a cyan at a white wall and noticed the white turns red? Also I was surprised to shine the cyan light at brush outside and have the twigs and limbs reflect almost as white compared to the foliage.

My observation of colored LEDs is similar to yours. Some people have claimed that colored LEDs do not render ANY colors but my experience is contrary to that. Some colors are rendered. Some very close to reality, some appear a different color or shade, and some are undiscernable.
It may be fluourescence, but you can see color, not just black, white and gray.

Here's a link to my posts if you haven't alredy seen them. Check all three pages:

Here

Sorry, I want to clarify my previous post about the white light looking red. Under the right conditions the white seems to reflect with a faint red cast. This is more noticeable if you have both lights shining on a small object near the wall from different directions that casts shadows on the wall. You should see the shadow cast by the white led light is green and the shadow cast by the cyan led light is red.

As far as certain colors being visible under blue light, I noticed 2 things:
1. The type of object surface varied; plastic, fabric, painted wood, paper, etc. But not all objects of the same color were visible that way or to the same degree.
2. I took pictures of the visible objects with my digital camera, just to prove I'm not mistaken. And sure enough, there they are - a dark room, blue light making everything black or shades of blue... and a patch of bright orange or yellow from the objects in question!

I've noticed this once or twice with my camera as well, but I'm wondering if it's an artifact of the CCD. I haven't really noticed it directly (with my own eyes). Of course, there's the possibility that you're just seeing the afterimage burned into your retina...

First, LED's aren't necessarily pure wavelengths (as opposed to lasers); some have fairly wide mainbands, and some have extra spikes in bands fairly well removed from the main one. So, a bit of ordinary reflected colors other than the main one may be perceived occasionally.

Second, fluorescence will convert frequencies, usually downwards, even in objects you didn't expect to do so. I've found that many red objects will glow a dull red in blue light, even though they aren't what we'd call flourescent in color. I found all kinds of interesting dull red glows by wearing red sunglasses while shining my 470nm blue X5 around. Even the clear plastic in the LED's themselves glows a dull red in that light! Fluorescence can occur anywhere in the band, but we usually only start to see the effects at green because only at that point is there room below it in the visible band for the source and effect color to be seen.

Lastly, the human eye has a sort of auto color adjustment in it, in part because of pigment level changes in response to the light. I was wearing those same red sunglasses to an outdoor basketball game to check someone's claim that I'd be able to see the ball better. It didn't help my game, but when I took them off indoors, the entire world was a very rich cyan color, as there were plenty of green and blue pigments in my retinas, but the red ones were tapped out.

Canuke hit it right on the head on the first two points. Fluorescent objects absorb the high frequency wavelengths and re-emit them at a different frequency. Draw with a fluorescent set of markers and a regular set of markers on a piece of paper and then hit that paper with a blue LED in a completely dark room. The normal marker drawings will show up as you would expect - shades of blue and black. The fluorescent marker drawings will show up in their proper colors since they are converting the blue light to the color they are made to fluoresce in.

LEDs do have a fairly wide central band and are not truly "monochromatic" - as a result you will get some spectral spillover and you may see some colors that are near to the primary frequency emitted.

The human eye does have an auto color adjustment, but whay Canuke describes is actually pigment bleaching. Wearing red glasses "uses up" all of the red detecting pigments in your retina. When you take them off, you see all the colors except red for a while, until your eyes can build up the pigment again. In the meantime, you'll see things in green and blue shades only. If you take the color "white" in "Paint" or another computer graphics program, and reduce the red to 0 while leaving green and blue at 255, you'll get cyan - exactly what you see when the red pigments in your retina are bleached out. Cool stuff!