Color determination from infrared photo?

Status
Not open for further replies.
C

ctdonath

Member
Joined
Jan 9, 2003
Messages
3,618
Location
Cumming GA
(While not gun related, this is security related, and of current relevance.)

Mindbender: given a photo taken with an infrared camera, is there any way to discern to any degree the color of cloth photographed? (Lighting conditions were poor.)
 
it depends on the camera... a professional processing lab could probably recreate the image in full visible color... but that would be beyond most peoples capability...

IR is a wavelength of light, and different colors and materials will reflect it differently, so determining what each of the surfaces is can be done, but it would most likely be a painstaking process of trial and error...

a lot of cheaper IR cameras, specifically digital ones are cameras that use full spectrum + IR and then filter the non IR info out in the processing chip... this is why a lot of them can be used for both purposes, so it is possible that some of the color information is retained in the produced image, though it might be in code fragments instead of visible pixels...
 
I have B/W IR security cameras and fabric is the hardest thing to guess color from contrast. Black fabrics can look grey to white Reds look very hot. On the up side I can tell if your car was partially repainted. I say no. :)
 
It would be very tough to reproduce color accurately, for the reasons the other posters stated.

Ever paid attention to how much the color of things change under "Black Light"....ultra-violet? Same for the Infra-red, but not quite as much in my experience.
 
I know nothing about how IR cameras work but a great deal about color. Human color vision is based on our response to the various degrees of intensity of the visible wavelengths of light reaching our eye. You would have to retrieve that distribution or a way to predict it from the picture that the IR camera has taken.

Some systems have generated pseudocolor from processing differential IR wavelengths with systems mimicking how our eye works but that won't be veridical with our perceptions, just adding some info to the IR picture above and beyond a 'gray scale' IR picture.
 
an IR camera is basically a camera that captures a very specific wavelength of light (monochromatic). What we observe as the color of an item is simply the wavelength of the light which is reflected by that item. A camera which does not capture, say, blue light, cannot "see" anything which reflects blue light. Same with red and green and all the other colors. There is no way to determine what color an item is with an IR camera. That's like asking if you can determine the color of something from a B&W photo.

Even trying to guess by using different colors and comparing the brightness won't work - two identically blue cloths may reflect IR in completely different ways, due to differences in the cloth itself or even the dye.
 
The amount of IR light reflection from fabric can be greatly affected by "brighteners" in laundry detergents, regardless of color. Brighteners increase the IR reflectivity of the fabric, which makes the colors appear brighter to human eyes (and animal eyes) without actually changing the visible color spectrum. Atsko makes a product that dulls the IR reflectivity of fabric for hunting clothing http://www.atsko.com/products/uv-protection/u-v-killer.html. The same concept would apply to an IR camera. So, the brightness or tone of an IR image of cloth could vary significantly for any given color, depending on the presence or absence or fabic brighteners or "dulleners."
 
I have to concur with posts 6-8. There are too many variables to determine color, unless you star on CSI in which case someone will be able to do it. But if you do figure out a way, be sure to post it. Lots of people would be interested.
 
I work with an infrared camera. I am a electrical engineer and we use the camera to measure the temperature of our circuits.

Obviously "my" camera will probably be different than a typical infrared monitoring camera, but this much I can say...

The colors you see on the infrared image have nothing to to with the actual color of what is being photographed. The color of the image represents the temperature and is scaled according to the particular settings of the camera. My color scale is adjustable based on what the temperature of my subject is, and I can also select the limits. An infrared camera used to take images of room temperature items, and those slightly above (a human or animal), will probably have a preset range and limits... and even if this particular camera mixes the image with a visible light image (I don't know if such a camera exists), there is no way of telling what is mixed and in what proportions, and to "undo" the image you would have to know what the temperature of the body was that was being photographed, and this can only be assumed, and then you would have to do the algorithm in revers, so I'd still say most likely not possible.

The only way to know for sure is to talk to the manufacturer.
 
You are correct, brighteners are UV. Ir is monochromatic. For full color an image intensifier can be used. You can get very low light full color images with some cameras. There are hacks for some conventional cameras to overlay the IR with the RGB data for a somewhat full color low light picture. I am no expert though, just a dabbler.
 
Status
Not open for further replies.
Back
Top