Clouds in infrared

[Howard Brown]

Infrared has been on my mind, then Michael mentioned Andrew Kirk from Owens Valley beside the Sierras, then my first search produced this which I could not resist posting – even a Michi Lauke in Phoenix. But perhaps you all can help me understand infrared more?
https://www.google.co.uk/search?q=infrared+cloud+photos&biw=1113&bih=668&tbm=isch&imgil=IDc22DIJJAcB4M%253A%253BCsiQLTuE–JbgM%253Bhttp%25253A%25252F%25252Fbishoppeakgroup.net%25252FLandscape%2525252520Images%25252FCalifornia%2525252520Mountains%25252FEastern%2525252520Sierra%2525252520Index.htm&source=iu&pf=m&fir=IDc22DIJJAcB4M%253A%252CCsiQLTuE–JbgM%252C_&usg=__3AYSYLMU2U0rYFEASEDvPUnndJo%3D&ved=0ahUKEwiM_pGZ1IbSAhVLJsAKHfofA8cQyjcIMw&ei=YEmeWIzOHcvMgAb6v4y4DA#imgrc=IDc22DIJJAcB4M

[Michael Lerch]

Think of Infrared as..photography with heat.. or of heat..

[George Preoteasa]

Infrared lies on the spectrum below red, so we humans don’t see it. Whatever is captured by the sensor needs to be shifted into colors that we can see (transposed like a musical piece written for a baritone when a tenor would want to sing it). Black and white is a bit different, in that, just like with visible light, colors disappear and only the intensity of the light is captured.

Anyway, there are two situations. If there is sunlight (which contains infrared), what you capture is the reflection of that light by the clouds (or other objects). The clouds do radiate some infrared, but what comes from the Sun is so much more intense. What makes those pictures so sharp is the fact that the infrared light is scattered very little, even less than the red light.

If there is no sunlight, then what the infrared sensitive film or sensor captures is the radiation emitted by bodies, the hotter, the brighter. Police and military uses come to mind, for instance a person hiding in the dark becomes a bright target when looked at with IR goggles.

IR cloud cover pictures taken by satellites reveal the cloud temperature. The tops are cold so one can tell how high the clouds are.

[Howard Brown]

Thank you, George, that’s very helpful. It would not have occurred to me about the sharpness. One thinks of heat dissipating quite quickly with distance but I suppose that does not apply to the infrared light.

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