IR photography

[Squirrel Girl]

Jim Thompson has been posting up recently on his thermal camera work looking at cave entrances.

Now, someone posted to a cave diving forum about using IR film in U/W caves. That's just near IR film (maybe shortwave IR). Unfortunately I know more about longwave IR. Anyhoo. A respondant suggested that in a water filled cave, everything would be the same temp and your picture wouldn't come out too well. They thought an air filled cave would be better. But I think an air-filled cave would be pretty equilibrated, too (entrance area, and human subjects aside).

So, here I am, posting up. Anyone tried this? Anyone have any idea?

[piers]

It might be interesting to take some near-IR photographs. Some formations and features may look different. The pictures you see where the foliage looks white and showy and people's skin looks like marble are near-IR pictures. Near-IR pictures of objects can produce surprising results (which is why near-IR, like UV, is used in document analysis). May be time to modify one of my DSLR's to take out the "hot mirror".

If you want to try film, the Konica-750 with a red filter (to cut it's sensivity to cyan and only use the 750nm sensitivity) is cool. Your regular xenon flash will produce plenty of IR and makes a perfect light source.

I have a feeling the caves around here may not be that interesting, but you never know unless you try!

Piers
http://www.CSIflashlights.com

[Tlaloc]

Infared film for your camera is properly referred to as false color infared film. It's sensitive to near infared just barely outside of the visual range. Another example of this is night vision scopes. You can illuminate the subject with near IR but you won't see the illumination with your eye. Thermal IR is far IR. Devices that make images of the different temperatures of objects are sensitive to far IR. Generally these devices use super cold detectors. They use electronic imaging devices that scan or are digital, NOT film. Also they don't use lenses like those in your camera because the glass lenses are designed to focus visible light.

The temperature of the objects you are photographing has nothing to do with the images created by IR film. It would be interesting to take some cave images with it but the uniformity of the temperature would have nothing to do with the results.

[wyandottecaver]

I also dont know about false IR. But Thermal IR in caves does work. (thus the idea that everything is the same exact temperatures is not quite true) we were using it to look at bats, but you can see differences in walls vs passage. this is because the sensors are detecting VERY small temperature changes (about .1 deg) and the air is always just a bit different from the rock. You can often even see differences between upper and lower areas since there is often a layering of warmer vs colder air even if the temperature difference is small. However, it is not uncommon for there to be larger differences of up to 5-6 degrees in larger spaces

[Squirrel Girl]

Thermal IR is far IR. Devices that make images of the different temperatures of objects are sensitive to far IR.

Close, but not quite. Thermal IR is Longwave IR, about 8-15 micrometers. Far IR is beyond 15 micrometers.

[piers]

Infared film for your camera is properly referred to as false color infared film. ....

Well, Kodak make the famous HIE 'high speed infrared' and Konica make the Konica750, both of which are black and white. Fuji probably has one too. Kodak EIR is the color film, where each layer is sensitive to a slightly different wavelength of near-IR radiation and hence produces a false color effect.

Having you DSLR modified so that the hot mirror is removed and the camera is sensitive to (near) IR and UV provides more feedback and flexibility, probably, for most folks.

As noted, this is completely different that thermal imaging which would be used to detect hot and cold spots and of course study bats and other animals.

So, for scientists, thermal imaging is more useful. For photographers looking for yet another interesting angle, try taking some near-IR photographs and let us see them!

Piers
http://www.CSIflashlights.com

[piers]

Infared film for your camera is properly referred to as false color infared film. ....

Well, Kodak make the famous HIE 'high speed infrared' and Konica make the Konica750, both of which are black and white. Fuji probably has one too. Kodak EIR is the color film, where each layer is sensitive to a slightly different wavelength of near-IR radiation and hence produces a false color effect.

Having you DSLR modified so that the hot mirror is removed and the camera is sensitive to (near) IR and UV provides more feedback and flexibility, probably, for most folks.

As noted, this is completely different that thermal imaging which would be used to detect hot and cold spots and of course study bats and other animals.

So, for scientists, thermal imaging is more useful. For photographers looking for yet another interesting angle, try taking some near-IR photographs and let us see them!

Piers
http://www.CSIflashlights.com