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What is the difference between an infrared filter and an ND filter? I have a big stopper and I would like to take some images to show the infrared spectrum I have seen images where green foliage shows up red and any heat source shown up white §Is there any lens filter recommended for this genre of photography

xiota
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tblane2
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1 Answers1

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ND stands for "neutral density" - it is a filter type that (in theory) absorbs all wavelengths of the visible light by the same amount.

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Effect of a ND-filter. CC-BY-SA 2.0: Robert Emperley

IR filters filter out all but certain wavelengths - the (near) IR wavelength of the filter. So basically, they are IR-pass filters, not IR-block filters. Thanks @TheLuckless!

As @Hueco states in his comment, IR filters will cut everything below a certain value. That value might be between 650 and 720nm - visible light, however, does go up to 750nm. Thanks for clarifying that, Hueco!

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Typical result of using an IR filter. Some effort was put into post-production: The red and blue channels were swapped. CC-BY-SA 2.0: Jannis

What you think of (white heat source, everything else red-ish) is most probably a thermographic camera - they differ from regular cameras in a lot of ways, including lenses that are (typically) made out of Germanium.

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Thermographic image. CC-BY-SA 3.0: Lutz Weidner

flolilo
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    It's important to note that most IR filters block somewhere between 650nm and 720nm and below. Important because visible light goes up to ~750nm. – OnBreak. Apr 05 '19 at 21:50
  • @Hueco Is there something you do not know better than me? :D In all seriousness, though: Will include that ASAP - just looking for some CC-BY-SA sample pictures for the respective categories. – flolilo Apr 05 '19 at 21:52
  • lol. I just happened to start looking at getting a camera converted by the folks at life pixel (many hours spent researching this topic). I'm just not sure if I want to send in the 60D or get a cheap used Rebel for the job. I do love my film, but when it comes to IR shooting, digital wins hands down – OnBreak. Apr 05 '19 at 21:56
  • While rare to find in the general photography world as a standalone piece, it is also good to keep in mind the existence of IR Block filters, as they are rather distinct from IR Pass filters. We might also want to highlight Near IR, as used in with "Infrared film", vs Far/Deep IR. [Which I think might be strictly digital for all practical purposes.] - Answer's original wording partially hides that they're both classed as part of IR Photograph. – TheLuckless Apr 05 '19 at 21:58
  • @Hueco Funny story - I am thinking about that for some time now, too. :-D Well, at least it's on my will be bought at some point in my life-list...a list that also features several fast primes and the tripod (technically I'm in the buying-process, but my favorite seller has health issues, so..I'm waiting ;-) ). BTT: Wouldn't a mirrorless be good, too? I mean: As far as I understand, the OVF is practically useless (for exact metering, that is) with IR. – flolilo Apr 05 '19 at 22:19
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    @TheLuckless Hopefully I integrated the information from your comment so that this is more clear now - thanks for the tip! – flolilo Apr 05 '19 at 22:20
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    @flolilo – OVF is useless with IR. When I had an IR-converted Rebel, there was no consistent exposure compensation that would work. Autofocus didn't work. Had to use Live View and manual focus to get reasonable results. Mirrorless with LCD or EVF would work better. – xiota Apr 06 '19 at 06:22
  • @Hueco – I'd recommend against using a Canon camera for the conversion. I had an IR-converted Rebel, and the sensor was IR insensitive compared with an IR-converted compact camera I have. It worked, but the shutter speeds weren't very good. I suspect the Bayer filter in Canon DSLRs blocks significant amounts of IR. – xiota Apr 06 '19 at 06:25
  • @Hueco – Infrared photography—why are green leaves not appearing as white? – xiota Apr 06 '19 at 07:02
  • @xiota that’s good to know about Canons. My only other real setup is Pentax 645 stuff. That’d be an expensive IR camera if I went that route. – OnBreak. Apr 06 '19 at 16:40
  • @Hueco - What I'd look for is a full spectrum conversion that shows bright pink foliage when used with no filter. Then you'd know the sensor is plenty sensitive to IR. With the Canon, it was possible to take normal pictures with no filter just by setting WB. I keep looking at m4/3 cameras with kit lens. Then I'd get adapters to use manual lenses. But I don't know how sensitive the sensors are. – xiota Apr 06 '19 at 17:59