AFAIK, remote controler operates by sending infrared light of a certain frequency to a sensor on your TV. That light is invisible to unaided eye - but when I pointed my digital camera to remote controler, I was surprised to see white glowing LED on camera display. How is it possible? Also, is it posible to detect other sources of invisible light using common digital camera?
Some cameras (especially among the cheaper variety) have CCDs which are sensitive to light frequencies slightly beyond normal human vision, including infra-red, which is why it can see your TV remote. Some wiseguys use them to look through people’s skimpy clothing.
Maybe you left the winkie smiley of the end of your post.
The CCDs on pretty much every camera are sensitive to near infra-red. And it’s not hard to disprove the “skimpy clothing” thing, simply by looking at any digital photo of a person.
The CCD of any old video camera will pick up infra-red. There is a low light setting on some newer cameras that apparently makes it fairly easy to see through certain types of clothing if you use it in full sunlight. Don’t confuse one with the other though. A regular video camera isn’t going to make people’s clothing see-through.
Cite?
Here’s a cite for you. The ability of cameras to “see” through certain clothes, specifically wet swim suits, was first noted with the Sony handycam night vision cameras. These cameras took advantage of the infra-red sensitivity of the CCD to allow night time photography using bright infra-emitting LEDs on the camera. Unfortunately, people discovered that you could put heavy filters on the camera lens and use it during the day, say, at the beach to take pictures of fabrics that are translucent to infra-red radiation. Although considering that the result was green, grainy, and not very distinct, I can’t imagine that the results were particularly erotic. Still, Sony reworked the cameras so that the night vision mode only worked at night (basically, there’s an internal infra-red filter that’s normally in place and that makes the camera less sensitive to infra-red radiation – this filter is only retracted in night vision mode and somehow, they modified the behavior). This is sort of annoying, because I have a Sony digital camera with night framing that only works in certain modes (possibly for the same reason) which makes it a much less useful feature for photography.
As to the OP, despite the presence of an IR filter, most digital cameras are sensitive enough to IR to pick up the emissions from a remote. You can also get weird color renditions if, for example, you take a picture of something very hot, like a stove burner. My old digitial camera would render burners as bright violet. I’ve also seen some strange color renditions in flowers and this may be because they reflect strongly in IR or possibly ultraviolet.
Here’s a couple of cites in return.
Hmm. Japanese men’s magazine. :dubious:
Note that in the sample photo, you can’t actually see through the swimmers. On the guy on the right, there’s a shadow that might possibly be a pair of Speedos underneath the board shorts. If you blow the image up, you can see that it couldn’t possibly be that, unless the guy is wearing the strangest shaped pair of Speedos I’ve ever seen.
Second cite is from Snopes (Warning, not work safe):
Japanese men’s magazines have this thing about see-through cameras.
OK. The plausible sounding explanation about the “x-ray see through filters” is:
a) they block visible light, and only allow near infra red to pass through; and
b) some synthetic fabrics are transparent to near infra red; and
c) you can see the reflected near infra red image of the body through the transparent clothes, because the visible light reflection from the clothes has been removed by the filter.
I have several problems with this explanation.
Firstly, none of the sane-sounding websites I was able to find had photos better than the one I linked to in my first cite.
Secondly, for several years, I used a baby monitor consisting of a CCD camera with infra red illumination. There was no need for any fancy filter to block out visible light, because at night, there ain’t any. There was never any hint that you could see a belly-button through anything.
I call bullshit.
Well, it’s one thing to be skeptical. It’s another to be just stubborn when a few minutes search on the internet can prove you wrong. Here’s a work-safe
example involving a mannequin, a black dress, and an infrared filter. They also show the ability of the infrared light to penetrate an ink spill on a document – a considerably less shady use of the technology. Probably the reason you haven’t seen more examples on the internet is that the results are grainy, monochrome, and not very distinct, while, as further perusal of the internet will demonstrate, there’s just no shortage of attractive young ladies who are happy to just take their clothes off and let the photographers take their pictures.
As for your CCD camera example, I don’t really think you can compare the output of a few IR Leds with the amount of IR radiation on a beach on a sunny day.
I was intrigued by the sunglasses photo on the site you linked to. It’s on this page (warning, not work safe):
http://www.kaya-optics.com/products/applications.shtml
In the photo on the left (no filter), the glasses are black. In the photo on the right, the glasses are transparent.
So I took some photos of my own. Look here. There’s three photos.
The first photo was taken with an ordinary digital camera, using visible light. Note that all four pairs of sunglasses are pretty much black.
The second photo was taken using the infrared CCD baby monitor I mentioned above. (It’s a crappy picture, because it’s actually a photo of the TV screen that the baby monitor used to display on.) Note that you can readily see through the bottom pair of glasses, you can see a bit through the next pair, and you can’t see anything through the top two pairs.
The third photo is a copy of the first, but with the gamma increased. (Gamma adjustment is combined brightness/contrast adjustment.) Now I can suddenly read the newspaper through the bottom two pairs of glasses!
The thing is, I could read the newspaper perfectly well through both of the pairs of glasses at the bottom of the photo anyway, using my own eyes.
The second photo may look revealing when compared to the first, but it really isn’t, because it doesn’t reveal anything that:
a) I couldn’t see with my own eyes, or
b) Couldn’t be seen after a bit of fiddling with a photo taken by an ordinary camera.
I’d guess that the dress they used in the mannequin shots that you linked to was transparent to visible light, just like the photo of Alexandra Kerry on Snopes (warning, not work safe):
So there’s really no magic in this, it’s just a con.
Your conclusion confuses me. We've already established, in the OP, that CCD cameras are sensitive to frequencies that the human eye can't perceive. It's not much of a stretch to believe that some fabrics are translucent to these frequencies. (You might experiment with your infrared camera to demonstrate this to yourself.)
Once you’ve established that, there’s nothing left to be skeptical about.
Your sunglasses experiment doesn’t seem to prove much. First, because sunglasses are designed to be seen through, after all. And second, because it seemed to actually demonstrate the opposite of your conclusion. If you had to increase the gamma of the camera in the visible range, but your cheesy insensitive IR camera had no problem seening the print, it means the sunglasses are more translucent to light in the infrared. Which is pretty much the point.
One issue relevant to the OP that I forgot to mention is that there’s a thriving band of hobbyists who like to take infrared pictures with digital cameras just for the artistic effect. You can get some eerie and often striking black and white or false color landscapes by using only light in the the near-infrared.
I’ve got one of those older handycams and the IR filter so I can confirm the phenomenon works (though not very well)
It might not be a stretch to believe this, as you obviously do. It’s quite another thing to demonstrate it.
Sure. Except that it hasn’t yet been demonstrated.
Ah, now, that contradicts your cite, and the photographic evidence that they provided. The sunglasses couldn’t be seen through, except by their magic filter. Look at their photographs.
WTF are you talking about? Both cameras were able to see through the glasses, as could I, without the benefit of a magic filter. The point was that in the first photo, it appeared that the camera couldn’t see through the glasses, when in fact it could.
I’ve gotten some of the aforementioned effects using my camera (a Fuji S5000), and—this is the important part—an IR filter. Not an IR filter like the “hot mirror” in some digital cameras meant to block IR light that will register on the CCD and throw the color balance off. But rather, it’s the “cold mirror” type that blocks all visible light and only lets IR through (Tiffen 87). (Hereinafter, when I say “IR filter”, I mean a filter that only passes IR light. Just like a red filter only passes red light.)
Now, I didn’t use any unsuspecting victims for the x-ray experiments. The mostly-suspecting victim was my wife. Conclusion: if it’s really, really sunny outside, and the subject is wearing the right combination of clothes, you can see outlines of underthings. But not too surprisingly, when this is possible you can usually see the same outlines with your naked eye.
FWIW, the notorious Sony Handycam ability existed because early revisions of the camera allowed you to activate “Night Shot” in broad daylight. That mode actually places an IR filter in front of the lens, just like I added a cold mirror to mine. So it’s the exact same effect.
As far as a resoponse to the OP, it’s been pretty well addressed, but I’ll sum it up. The CCD (sensor) in your digital camera is sensitive to IR light. It’s not just cheap cameras…all CCDs are sensitive to IR by their very nature. Different manufacturers put varying amounts of filtering inside the camera to avoid this, because it can skew your color balance in a real image. So some cameras respond to the remote better than others. If you could remove the hot mirror from inside the camera, you’d find that the LED on the remote glows blindingly bright. What you see now is probably greatly-diminished image as the small percentage of the IR that does make it through registers as a purple dot.
Do a Google search for infrared digital photography to get a better handle on this.
I’m talking about exposure – something all photographers know about. Except possibly you. If you had to increase the gamma on your photo, it was underexposed. It was underexposed because not a lot of light was getting through the lens. In the CCD shot, it was obvious that plenty of light was getting through the lens – it appeared as if the tint in the sunglasses wasn’t affecting the IR very much. Which seems to demonstrate the not very difficult point that sunglasses absorb light differently at different frequencies.
:rolleyes:
No, it most definitely does not. In the first shot (call it underexposed visible), all of the sunglasses looked dark. In the second shot (CCD) only two of the sunglasses looked dark, and two didn’t. In the third shot (call it properly exposed visible) two sunglasses looked dark, and two didn’t. Which is exactly as it appeared to my naked eye, and to the CCD infrared camera. Let’s look at the claim in your cite:
The claim is simply bogus. The CCD camera could see through the two cheap pairs of plastic glasses, but couldn’t see through the Raybans or the Bolles. But an ordinary everyday digital camera could also see through them, if used properly, and I could see through them myself unaided anyway.
OK. The T-shirt shot that appears on the same page of your cite as the sunglasses. The magic filter can see through the T-shirt.
Look at my photos here (work safe).
The first photo shows a book inside a black stocking.
In the second photo, look! magic! You can see straight through the stocking at the book underneath! It’s green and everything! Must be the result of a magic infrared filter!
Except that the second photo is just a photo-shopped version of the third photo, which was done in visible light, just by changing the direction of the lighting.
So, again, I call bullshit.