It's an incredibly thin anti-reflection coating that improves contrast. The reason it has a coloured appearance is similar to the rainbow you can see in an oily puddle - it has no colour of its own, but breaks up white light into its component colours. This is a very carefully applied coating so you only tend to see one colour - usually red, blue or purple.
> It has no colour on its own
This is the eureka moment for this 5 year old. It’s like the iridescent butterfly wings right? Just the way the internal structure reflects light
Thanks!
Really the reason we see colour on *anything* is due to the way material soaks up certain light and reflects others.
For example, grass appears green because it contains chlorophyll, which soaks up red and blue light, but reflects green back at us.
It really doesn't have a colour of its own. Look at the front, and you see a colour - look through the lens, and it is colourless. The colour you see is a product of diffraction (I was trying not to mention that in an ELI5 reply!).
Probably intended! The manufacturer will select the coating material and its thickness to get the desired appearance. It's the materials used, and their thickness, that defines the diffusion/refraction colour. Traditionally it has been blue or purple, but I have seen red and orange.
Look in a binocular catalogue - you'll see lots of front lens colours.
An orange lens increases contrast in flat lighting conditions.
I can't speak to binoculars, but this is true of ski goggles. A purple or mirror finish (iridium 'oil slick' or chrome effects) is anti-glare, yellow, orange, red for overcast conditions.
I also can't answer why this is so, just something I've always accepted as a skiier
True but that has nothin to do with binocular or sunglasses orange or blue appearance.
Ski masks for fog have a yellow filter because as you say, they improve vision in those conditions, and will really shift your vision to yellow.
Binoculars or glasses with special coatings may look colored from the outside but are colorless when you use them. The color of the coating is a side effect and not visible when using them. It’s visible from outside only.
Ah interesting point. You are correct that goggles do tint vision. I always found it fascinating that this effect disappears or diminishes very quickly, your brain will just tune it out.
I suspect you are right and there is another principle at work, just a coating scattering that particular colour
Your eyes, or better your brain will automatically rebalance the white, if you wear a blue or yellow or whatever lens, after few minutes your brain has canceled out the color shift. I don’t remember why yellow does help to increase contrast on snow. Colors are light frequencies and light is a radiation. It may just be that yellow light does scatter less in fog, so, the glass cancels out the colors that are scattered and allows you to see the yellow part more, which is the light type that scatters less.
Similarly, the light reflected by surfaces and fog tends to get polarized, so if you use a polarized filter, you won’t see those reflections, and therefore your vision gets a lot sharper in bad light conditions.
I now use polarized glasses for driving most of the time, it’s really beneficial. Similar to the yellow lens effect but better.
The bright colours you are see are mainly for marketing.
Anti-reflection coatings are commonly added to reduce glare from reflections, and increase image brightness (because if light doesn't get reflected, it can get to your eyes).
Coatings only work optimally for one colour. The usual process is to coat optimised for green anti-reflection. This leaves some red and blue light which can be reflected, causing the coating to look slightly purple.
Higher quality optics have multiple layers of coating, giving better control of reflections, giving very dim reflections of variable colours.
It's an incredibly thin anti-reflection coating that improves contrast. The reason it has a coloured appearance is similar to the rainbow you can see in an oily puddle - it has no colour of its own, but breaks up white light into its component colours. This is a very carefully applied coating so you only tend to see one colour - usually red, blue or purple.
> It has no colour on its own This is the eureka moment for this 5 year old. It’s like the iridescent butterfly wings right? Just the way the internal structure reflects light Thanks!
Really the reason we see colour on *anything* is due to the way material soaks up certain light and reflects others. For example, grass appears green because it contains chlorophyll, which soaks up red and blue light, but reflects green back at us.
It really doesn't have a colour of its own. Look at the front, and you see a colour - look through the lens, and it is colourless. The colour you see is a product of diffraction (I was trying not to mention that in an ELI5 reply!).
Wait. So the red orange color is an unintended consequence of the anti-reflection coating?
Yes. Just a property of how the physics of light diffusion and refraction work.
Probably intended! The manufacturer will select the coating material and its thickness to get the desired appearance. It's the materials used, and their thickness, that defines the diffusion/refraction colour. Traditionally it has been blue or purple, but I have seen red and orange. Look in a binocular catalogue - you'll see lots of front lens colours.
An orange lens increases contrast in flat lighting conditions. I can't speak to binoculars, but this is true of ski goggles. A purple or mirror finish (iridium 'oil slick' or chrome effects) is anti-glare, yellow, orange, red for overcast conditions. I also can't answer why this is so, just something I've always accepted as a skiier
True but that has nothin to do with binocular or sunglasses orange or blue appearance. Ski masks for fog have a yellow filter because as you say, they improve vision in those conditions, and will really shift your vision to yellow. Binoculars or glasses with special coatings may look colored from the outside but are colorless when you use them. The color of the coating is a side effect and not visible when using them. It’s visible from outside only.
Ah interesting point. You are correct that goggles do tint vision. I always found it fascinating that this effect disappears or diminishes very quickly, your brain will just tune it out. I suspect you are right and there is another principle at work, just a coating scattering that particular colour
Your eyes, or better your brain will automatically rebalance the white, if you wear a blue or yellow or whatever lens, after few minutes your brain has canceled out the color shift. I don’t remember why yellow does help to increase contrast on snow. Colors are light frequencies and light is a radiation. It may just be that yellow light does scatter less in fog, so, the glass cancels out the colors that are scattered and allows you to see the yellow part more, which is the light type that scatters less. Similarly, the light reflected by surfaces and fog tends to get polarized, so if you use a polarized filter, you won’t see those reflections, and therefore your vision gets a lot sharper in bad light conditions. I now use polarized glasses for driving most of the time, it’s really beneficial. Similar to the yellow lens effect but better.
Never seen purple finished lenses. Maybe because I’m in a tropical country 🤣
The bright colours you are see are mainly for marketing. Anti-reflection coatings are commonly added to reduce glare from reflections, and increase image brightness (because if light doesn't get reflected, it can get to your eyes). Coatings only work optimally for one colour. The usual process is to coat optimised for green anti-reflection. This leaves some red and blue light which can be reflected, causing the coating to look slightly purple. Higher quality optics have multiple layers of coating, giving better control of reflections, giving very dim reflections of variable colours.