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Old Jun 23, 2004, 10:41 PM   #1
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Here's a new Infrared picture I took today. Just converted to grayscale, cropped and sharpened a bit.



Here's a picture I took that was backlit by the sun.



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Old Jun 26, 2004, 9:46 AM   #2
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how you do that infrared picture???

thx
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Old Jun 26, 2004, 10:38 AM   #3
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That first one is very nice. It should feel cold but doesn't at all.


Pierre you might find this thread useful. http://www.stevesforums.com/forums/v...light=Infrared
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Old Jun 26, 2004, 3:58 PM   #4
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I read the other thread and found it interesting but it doesn't answer a basic question. If you take it outside on a pitch dark night and point it toward anything that is giving off heat, will you get an image? Or does it just filter everything from a daylight image except the IR range. It would seem to that an IR FILTER does not make the camera sensitive to IR but just allows the IR portion of daylight to reach the ccd.

Infrared film, on the other hand, IS sensitive to the IR range of the light spectrum. It can "see" heat images in the dark.
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Old Jun 26, 2004, 7:38 PM   #5
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You can, in fact, see heat IR images with digicams, but it has to be pretty hot. Same as with film. IR Film is sensitive only to the NIR spectrum and will record any image (given enough time) that falls within that spectrum. The same is true of IR in digicams. In fact, the basic sensor in a digital camera is far more sensitive to NIR than the best film. This is why ALL manufacturers place an IR filter over the sensor. Otherwise, your photos would look pretty weird (read: awful).

You cannot with normal IR film or the digital camera, capture IR images in total darkness (except with a high heat source such as a hot iron). IR is reflected off the subjects. Somethings reflect better than others. For example: Broad leaf trees reflect far better than pine trees, water and sky hardly reflect at all.

Obviously it is morecomplicated than these brief two paragraphs describe.There are several really good sources for NIR info on the web. Never mistake NIR for thetype of IR you see in night police chases, for example. Those images are caught usinghighly sophisticated and very expensive equipment withthe sensor essentially in a frozen or very cold state. IR film (and digicam sensors)WILL NOT capture these types of images.
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Old Jun 26, 2004, 9:37 PM   #6
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You're right, the filter does not make the camera IR sensitive. It just blocks all visible light (Depending on the strength of the IR filter) so that only the IR radiation reaches the CCD (Which prevents the visible light from overwhelming the IR image). Different cameras have different sensitivities to IR (All CCD's are sensitive to IR, but some companies put more filtering (Called a hot filter) in front of the CCD, so the IR doesn't interfere with the visible light image. The easiest way to test IR sensitivity is to point a IR remote at your camera lens, and the brighter the light appears, the more sensitive the camera is to IR. On some cameras that are not as sensitive to IR you will have to get a filter that only blocks most of the visible light. If you hold the Tiffen 87 filter (which I use) in front of you, you will not be able to see anything through it. I use a Minolta Dimage 7, which is the only camera of the Dimage line that will work with the 87 filter. The cameras that came after it added improved hot filters. What you see in the pictures is the light from the huge IR source (The Sun) bouncing off of different materials differently than visible light does. Which is what gives IR images their unique look. As to capturing images in total darkness. It depends on what you mean by total darkness. You can take an IR image in what appears to be totally dark conditions as long as you have a light source that only allows IR light to pass. This is what some of the less expensive Night Vision systems do (As well as Sony's Night-Shot system does). So, to you and me, it appears to be dark, when in reality, it is quite bright with IR light. I have even seen set-ups where scientists used flash units that had a IR filter over the flash head to take pictures in the dark without causing the bright flash of visible light. Viewingthermal images is further down the specturm beyond the Near Infrared. Systems that can see in this range actually need to be cooled (As Delos said) because theheat in the sensor itself, and the heat generated by the electricity powering it give off so much thermal energy that it would blind the imager.

I hope this answers some of your questions.
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Old Jun 26, 2004, 10:29 PM   #7
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For a fairly good example of IR vs Visible look a little further down in this forum or click on this link:

http://www.stevesforums.com/forums/v...amp;forum_id=8

The IR was taken with a #87 Tiffen and a Nikon D70.
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Old Jun 26, 2004, 10:41 PM   #8
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Is there an IR filter for Coken, specifically the P-series line of filters?
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Old Jun 26, 2004, 11:16 PM   #9
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I don't remember seeing one in their catalog. However they do have a holder for a gel filter, and I believeKodak does make a 3x3 and a 4x4 gel IR filter so you can use that.
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Old Jun 27, 2004, 1:39 AM   #10
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I thought I'd pop my head in again and thank Delos and photo_mage for the information.
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