HRPRG_Belinda, on Nov 7 2008, 12:36 AM, said:
I'm just wondering wouldn't using a light source of any sort compromise the infrared light? I mean I thought we are using infrared to see things that can't be seen with our eyes and by introducing light that our eyes can see doesn't that kinda defeat the purpose of spending all this money ot have true infrared?
It could compromise the situation, however there are actually two methods that can be used to photograph in a particular portion of the spectrum. Suppose you wanted to photogragh an object's IR properties. You could use an IR light source and take a picture using a camera which responds to all portions of the spectrum. Since it was illuminated using only IR, the reaction would be to only IR light.
Another option is to illuminate using all of the light spectrum including IR. Then using a camera fitted with an IR pass filter take the picture. Only the portion of the light within the IR spectrum would reach the film (or CCD) thus only the IR would be seen.
It sounds as though the results would be the same, but not necessarly. Consider that some materials have different properties of refraction. that is why certain materials irredesce under certain types of light. Thus characteristics can vary depending on the material present. Exactly how is a function of the camera, light source, and material composisition of the subject. Any or all of these can affect the results. Keep in mind too that many cameras are sensitive outside the spectrum where our eyes operate so results in a photo may be different than what is seen visibly.