IR Photography

[asterroc]

I tried out some IR photography this weekend (after a post on UV photography by txtriffidranch the other day). In the sequences below the cut, I have three images: normal visible light (technically, representative false color), a black and white version of the visible light image, and an IR black and white version. (I used an IR filter which blocked out all but the reddest of visible light and of course didn't block IR. Digicams are sensitive to a bit of the IR spectrum, so it sensed both the red and the IR and that became the image). If you want more explanation of the phenomena, I posted on my science blog about it.


From top of Mt. Holyoke, Skinner State Park, looking southwest.




Communications shack atop Mt. Skinner

Comments

[framefolly.livejournal.com]

Wow! Really startling changes -- and continuities! The second set, with the trees and sky, is particularly striking. Beautiful pictures!

[zandperl.livejournal.com]

One thing that really surprised me was the difficulty focusing the IR images. Firstly, the autofocus didn't work quite right - since IR light bends a different amount when passing through glass than visible light, the process the camera uses for visible light apparently doesn't work as well for IR light. The second problem was that when you block out all the visible light, the image gets much dimmer, so where the normal light images were taken at 1/200 of a second, the IR light ones were more like 1/2.5 sec, and at those lengths you start getting blurring from shaking the camera.

[seekingferret.livejournal.com]

I exploited CCD sensitivity to near IR at work, to track a 1060nm laser beam whose spot was invisible to the naked eye. It came out purple on the camera's LCD screen and in photographs taken with the camera, for reasons I cannot explain. (This was not using an IR filter, because we also wanted to see the surroundings)

[zandperl.livejournal.com]

I guess that means that both the red and blue sensitive pixels are also sensitive in IR. I'm a bit surprised.

FWIW it's my understanding that commercially available digicams generally don't use CCD technology, but CMOS. I'm not too clear about the distinction between the two, though I'm under the impression that until recently CCDs were preferred for astronomical use. I'm planning to grill a couple astronomer friends of mine about it, but if you know more than Wikipedia says I'd love to hear.

[rubicat.livejournal.com]

IR photography is fascinating. Of course, light itself is fascinating! :)

[zandperl.livejournal.com]

Birds have 4 types of color-sensing cells (cones) in their eyes: RGB and UV! I want a UV-only filter now! :)

[marquiswildbill.livejournal.com]

How far into the UV can birds see?
I'm quite intrigued because UV has enough energy to break a number of chemical bonds, so anything that is not near the visible light region would blind the viewer.

[zandperl.livejournal.com]

Now that I don't know, but I'm sure you can find papers on it. :) Let me know if you do look for it.

[q10.livejournal.com]

it might be that the normal camera optics filter out too much UV to make this practical - you might have to modify the internal filtering elements of the camera and/or procure a quartz lens.

[zandperl.livejournal.com]

I'm not sure; they do sell UV-filtering-out filters (I buy them for every lens I own just to serve as a protection against smudging and bangs), so the lenses can't get rid of all the UV. But I don't know.