Is it possible to see in infrared and regular visible light at the same time? Which colors would dominate? What color would a hot blueberry appear as?
If you mean with just your eyes, unaided, no.
If you mean with technology, sure. Every color and infrared combination would become the color or intensity chosen for that purpose.
Can you see all variations of visible light and infrared together at the same time though? No. That’s more variation than your eye can perceive now, so infrareds have to be mapped into the visible light that you can already see.
One example, you can take a red-green-blue photo and replace either of those colors with infrared to get something like
this. This one has replaced red with infrared, so the vegetation which reflects a lot of infrared shows up as red in the image.
Digital camera sensors see the entire spectrum, visible and IR. A low-pass IR filter in front of the sensor blocks the IR waves. Replacing the low-pass filter with plain glass gives an image like this.
This company also does other conversions, seen here.
I never thought about this before but now that you say it, it’s obvious. Perhaps this is a bit whimsical and unanswerable, but what would infrared light look like if you could see it directly? (and UV light for that matter)
It would look like infrared light. It sounds flippant, but think about what’s actually happening. Light hits receptors in your eyes that activate nerves that send a signal to your brain, which then assembles all those signals into a picture. If human eyes could perceive IR as well as the normal visible spectrum, it would simply be another distinct color.
The biggest difference between IR and normal light is that there would be many more light sources in everyday life, so we would likely have a completely different concept of illumination and shading.
An easy way to demonstrate this is to point a TV remote at a digital camera. When you press a button on the remote, the IR signal will be visible on the camera preview screen.
That depends on what you mean by IR. The infrared band is significantly wider than the entire visible light range combined, so it’s likely that an organism that could see infrared would either see only a small portion of it, or would break it down into a number of distinct colors. Near-IR vision wouldn’t look all that different from what we currently have, since near IR tends to be absorbed/reflected by most things in much the same way as visible light, and most near IR comes from sunlight or other sources that produce visible light too. On the other hand, if you could see far IR, then you’d start picking up things like animals as sources, or even seeing which parts of the ground and environment warm up quicker or cool off slower.
Yes, but the whole point here is that thermal cameras are just mapping the IR light to colors that are part of our visible spectrum - i.e. we aren’t actually seeing IR light with our own eyes. As Chipacabra says, the IR would be its own distinct color - which is something I am trying to imagine and wrap my brain around. Similar to how I’ve tried to imagine what the sensory experience would be like if I had 360-degree vision. I recognize the ultimate futility of this type of exercise because our brains are so grounded in what we know that to envision a completely different type of sensory experience pretty much just amounts to speculation. Still fun to try, though.
What if you look through an IR lens with one eye while the other eye views that same area in living color?
What about animals that perceive IR or, on the other side, UV? Bees can see part of the UV spectrum, which is why flowers that look “ordinary” to us have special patterns (visible for us with the digital cameras that map UV to visible light) to attract bees; but do they additionally have cones for visible light?
My laymen understanding was that other animals either have a more limited colour spectrum, or a shifted one - deer, I think, can see highest in infrared because that’s advanteous in the forest, but they lack other colours. I wonder if there is a biological maximum of how many cones/ receptors you can have in a normal eye, regarding energy need and brain capacity in interpreting - human eyes can already tire out, too. And the highest peak of the individual species covers the most useful part of the spectrum, so additional areas would not be worth the effort.
Could some cross-breeding / genetic tampering hypotheically result in a mammal with receptors for visible light plus infrared plus UV? How would that animal perceive the world, once it got used to the overwhelming sensual impression? I think that would be closest to what the OP asked.
I’m not sure what you’re asking for here. What is blue or green other than our brain’s response to a particular wavelength of light? The FLIR (and I saw a very cool presentation by Texas Instruments once) gives you the best example of what you would perceive the world to look like if you could see in infrared.
See the human color channel response chart in this article. That’s how your conscious brain is interpreting the differences in red/green and blue/yellow activation. You can extend those lines, shift them, or imagine what another channel would do to your perception.
The FLIR can show you what things standout in IR but the image displayed by a FLIR can be in any visible colour the engineers choose, normally a grey scale. So a FLIR image doesn’t really show you what things would look like unless you happened to perceive IR in greyscale which would be odd.
Maybe this is really more what you’re wondering about: if objects have some color, but then get so hot that you perceive some glow, then what would they look like? You can see thermal radiation from objects that are hot enough. Try it with an electric stove burner. On high, it glows orange-red, but at some setting it will just barely glow, and its appearance will be a mix of gray-black metal and red radiation somehow coming through. Which one dominates depends on how much of each there is. The darker you make the room, the harder it is to see the gray black component, and it looks more red. The lower you set its heat, the harder it is to see the red component, and it looks more black.
Also, this may be a cheat, but if you define infrared based on wavelength, you can see somewhat into the infrared if the source is bright enough. I work with infrared laser diodes whose light is plainly visible, but it is also extremely intense without looking bright. If it were that intense at a more visible wavelength it would be blindingly brilliant (and in a literal sense may still be, as there are certain hazards). The intent of the word “infrared” is that it’s under the visible red wavelengths, so by that definition when it’s visible it isn’t infrared. But by some definitions, you can see infrared.
The range of wavelengths perceptible to human eyes overlaps slightly with the wavelengths usually considered infrared. The eye’s response in that range is so weak that it’s usually not noticed. This article has instructions for using filters to block the spectrum below that overlap area so that infrared can be seen in bright sunlight.
Note 1: The method in this article can be dangerous. Your eyes are not good at recognizing dangerous intensities of infrared.
Note 2: Bill Beaty has great articles about electricity and other topics, but his site also hosts fringe science articles. If you follow links around, look for disclaimers and check which section you are in.
Put IR-transparent colour filters on a flashlight. Light it up when you’re in a completely dark room. What you’ll see is the range of IR light visible to the human eye (some overlap). Note that you’ll want to do this with a proper flashlight, not a maglite or something puny. Also, DO NOT STARE DIRECTLY INTO THE LIGHT.
Personally, I wouldn’t trust this demonstration: Just as your eyes don’t have a sharp cutoff, neither do most filters. If there’s some overlap between a particular filter’s transmissivity and your eye’s sensitivity, it’s hard to say how much of that is due to your eyes, and how much is due to the filter. That is, what you’re seeing might actually be red, not infrared.
Insects don’t have “cones” as such, but do have color receptors that may be tuned to different color frequencies like our cones are. Bees are trichromats, like humans, but see a different range of light frequencies because their receptors cover different parts of the spectrum (one of them is sensitive into the UV). Most insects are dichromats.
Most vertebrates other than mammals are in fact tetrachromats, with four types of color receptors, one of which can perceive UV. Birds see a far greater range of colors than we can, and it has recently been found that some species that appear dully colored to us are in fact brightly colored in UV.
Most mammals (including deer) are dichromats, with only two types of cones. Trichromatism has evolved in some primates, including Old World monkeys and apes (including humans) and a few New World Monkeys.