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Digital Infrared Photography FAQ



Digital Infrared Photography FAQ v1.0

digital infrared photography f.a.q. v1.0.2


Frequently Asked Questions (FAQ)
maintained by Eric H. Cheng (eric@echeng.com)
http://echeng.com/photo/infrared
last update 2001-Jun-14

  1. What is near infrared light?
  2. How do I take near infrared photos with my digital camera?
  3. Can I record heat using the methods outlined in this web site?
  4. What digital cameras can be used to record near infrared light?
  5. How can I tell if my camera can be used to record near infrared light?
  6. Where can I buy the camera accessories mentioned in the tutorial above?
  7. Why are my photos blurry or fuzzy?
  8. What are typical exposure times?
  9. Where can I find an infrared light?
  10. I thought CCDs were as sensitive to infrared as they are to visible light. Why are my exposures so long?
  11. Why should I take infrared photos with a digital camera (instead of using traditional film)?
  12. My infrared photos are red, and don't look like the ones in your gallery. What's wrong?
  13. Why doesn't my infrared setup work inside?
  14. Can I remove the hot mirror filter from my digital camera?
  15. Why don't my digital infrared shots exhibit the "IR Glow?"

1. What is near infrared light?

Near infrared light is the light in the spectrum just beyond visible red light (starting at a wavelength of around 780 nm). A good way to visualize near infrared light is to think of a common stove. When turned on, the stove coil will begin to radiate near infrared light just before the coils start to glow red.

2. How do I take near infrared photos with my digital camera?

Read through my online tutorial and this FAQ. If you still have questions, email me!

3. Can I record heat using the methods outlined in this web site?

Thermal radiation ("far infrared") and near infrared radiation are not the same. Recording "heat" requires special imaging equipment that is not commonplace in the consumer market.

4. What digital cameras can be used to record near infrared light?

Any digital camera that doesn't have a filter that blocks infrared light (also called a "hot mirror" filter) installed can be used to record infrared light. Most consumer digital cameras don't have hot mirror filters installed by default.

5. How can I tell if my camera can be used to record near infrared light?

Test your camera to see if it can see beams emitted from a common infrared remote control. These beams seem to be fairly bright and are easily seen in a camera's LCD preview area. If you don't have an LCD on your camera, your only hope is to try to capture the beam by taking a picture of your remote (while depressing a button on it). If you cannot see the infrared beam, you may have to remove the infrared blocking filter by disassembling the camera. Note that this may void the warranty.

6. Where can I buy the materials mentioned in the tutorial above?

28mm-37mm stepup ring for Nikon Coolpix 950 from CKCPower
Tiffen #87 glass filter from B&H Photo
Gelatin #87 and #87C filters from B&H Photo
Gelatin filter holders from B&H Photo

7. Why are my infrared images blurry or fuzzy?

Traditional focusing mechanisms are optimized for visible light. Infrared light focuses at a different focal plane, so it may be hard to get your photos completely sharp.

Make sure you're using a tripod and good quality filters. If you're using a home-made visible light filter or a #87C filter, try using a commercial #87 filter instead. The #87C may not be letting in enough light for you to get a sharp photo. If you're using gel filters, try using a glass filter. Tiffen makes a #87 filter ($92.50 at B&H), and B+W makes a glass #87C filter ($37.50 at B&H).

Other hints:
a. Try using smaller apertures so depth-of-field is increased
b. Set the focus at infinity for landscape shots

8. What are typical exposure times?

On my old Agfa ePhoto 1280 (which I believe was rated at ISO 100), typical shutter speeds with a #87 filter were 1/4-1/15 sec., outdoors in the sun. The Nikon Coolpix 950 (pushed to ISO 360) works somewhat better, metering shutter speeds of 1/15-1/45 sec. (again, outdoors in the sun). Pro digital SLRs can be set to work at ISO 1600, which should help getting shorter exposure times.

9. Where can I find an infrared light?

Sony makes infrared illuminators for their Nightshot camcorders (they run about $70-80 or so). You can also purchase an infrared flashlight, or build your own out of infrared LED (Light Emitting Diode) arrays. I've found sources online that will build custom lights out of arrays of infrared LED's, but I don't remember where I found them. In practice, I've found that Sony's infrared illuminators don't work as well for digital cameras as they do for camcorders. I've managed to get useful illumination from close up, but shots in complete darkness (illuminated with a Sony infrared light) require very long exposures.

10. I thought CCDs were as sensitive to infrared as they are to visible light. Why are my exposures so long?

Although CCDs are roughly as sensitive to infrared light as they are to visible light, consumer digital cameras have filters that block out most infrared light. However, some infrared light gets through to the CCD, which is what we count on to digitally record infrared light.

11. Why should I take infrared photos with a digital camera (instead of using traditional film)?

Digital cameras are convenient and photos are free! Because digital cameras have LCDs that are used for real-time previews, we can preview the world in infrared. Infrared film photographers use Kodak Wratten #25 filters on traditional cameras in order to preview their images (which results in a red image), and are unable to preview their photos in infrared without fancy hacks (like piping a night-vision scope's image through the viewfinder).

12. My infrared photos are red, and don't look like the ones in your gallery. What's wrong?

You must use a filter that is completely visually opaque. Filters like #25's let in red light, which the camera is much more sensitive to than infrared. If you were to subtract out the red channel from your resulting image, you result might look like a more typical infrared image, but it's much easier to just use a #87 or #87C filter.

13. Why doesn't my infrared setup work inside?

Indoor lights don't typically give off much infrared light. I've successfully used halogens to illuminate subjects for infrared photography, but they just can't compete with the sun. :) You may also want to try dedicated infrared illuminators (info above).

14. Can I remove the hot mirror filter from my digital camera?

If you have a Nikon Coolpix 950 (or 900, or 990, I presume), check out James Wooten's page, where he details hot mirror removal from a Nikon 950 camera.

15. Why don't my digital infrared shots exhibit the "IR Glow?"

"The 'glow' is a result of overexposure and the fact that the anti-halation coating has been removed from Kodak's high speed IR B&W film." (thanks, Mike)

 

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