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Homebrew Camera Mod Mimics LANDSAT Satellite 21

Posted by timothy
from the for-the-neighborhood-watch-with-dea-ambitions dept.
An anonymous reader writes "These folks at Public Lab have published instructions to hack a conventional camera to do photosynthesis photography, just like NASA's LANDSAT satellite. What better way to introduce your kids to space technologies and learn more about the environment? Measure the health of your garden, all with a simple filter switch and some post-processing. It's thoroughly documented at http://publiclab.org/wiki/near-infrared-camera, and you can do it to a variety of cameras." (And here's a link to the related — and fully funded — kickstarter project.)
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Homebrew Camera Mod Mimics LANDSAT Satellite

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  • Infrared filter? (Score:2, Insightful)

    by Anonymous Coward

    DNRTFA, but can I assume that we're talking about removing the infrared filter that is integrated into most cameras made in the last 15 years, and the hack for which has been available on the net for just about as long? It was all the rage when people found out that you could take nudie pics at the beach with this trick.

    • Re:Infrared filter? (Score:4, Informative)

      by Anonymous Coward on Thursday June 20, 2013 @11:49AM (#44061251)

      The change is to *replace* the IR filter with a notch filter that just removes the visible red, while leaving the near IR and green/blue light. The combination is interesting for detecting plants.

          http://publiclab.org/notes/cfastie/04-20-2013/superblue [publiclab.org]

      • by skgstyle (625779)
        Is this better/worse/ or just the same as using a infra-red lens filter for (D)SLR cameras?
        • by Lumpy (12016)

          If you took a photo of a person in a perfect camoflauge suit, they will stand out like a beacon with this camera mod.

          It will work great for detecting non living organic things in camo easily.

          • by tgd (2822)

            If you took a photo of a person in a perfect camoflauge suit, they will stand out like a beacon with this camera mod.

            It will work great for detecting non living organic things in camo easily.

            Depends on the material. Some printed inks are transparent to IR, and you'll get basically solid white, some inks aren't and you'll still get the patterns. This "trick" depends on the fact that the chlorophyll in plants is extremely IR reflective, that's all.

        • by tgd (2822)

          Is this better/worse/ or just the same as using a infra-red lens filter for (D)SLR cameras?

          Those are the opposite. IR filters remove the IR.

          Digital sensors in cameras essentially always have a UV/IR filter built in (UV/IR filters for DSLRs are really just lens protectors).

          Its easy to remove the IR/UV filters in a camera and shoot photos that go pretty far into the IR and into the UV ranges. With the right filters, you can do all sorts of "sciency" photography like this, or "artsy" IR photography like you'd get with Kodak's B&W IR film.

          The top-level post is right, though -- there's nothing new

          • by skgstyle (625779)
            Maybe you are thinking of UV filters? I was referring to lens filters like this - http://www.adorama.com/HY58RM72.html [adorama.com] which only allow infrared rays above 720nm to pass through the glass.
          • by Obfuscant (592200)

            Digital sensors in cameras essentially always have a UV/IR filter built in (UV/IR filters for DSLRs are really just lens protectors).

            No, they don't. That's why there is an IR filter you can remove in front of them. It's buried in the camera itself in most cases, but many of the cameras I've used (machine vision/scientific, in particular) have the IR filter easily accessible and removable. And many of the color cameras I've used outdoors now have very odd colors because the UV has deteriorated the sensor's color filters for the R, G, and B.

            Why make two kinds of sensors when you can make one and then put a $0.50 filter in front depending

        • by jythie (914043)
          I would put it at worse, but only because this is a cheaper way of doing it.

          Usually what you have to do is either get a broad spectrum conversion then get a special cut filter or have the cut filter put in the camera.... or have a tri-shot monochrom setup so you can be extra sure which wavelengths are getting into which channel.

          What they are doing here is similar to the old trick of using exposed film as an IR filter or shards of blacklight bulb as a UV filter, they found a cheap substitute for the high g
    • by sjames (1099)

      That's step 1. Step 2 was to filter out red light instead (making the red channel of the photo be an IR channel) by finding an off the shelf filter that happens to do the needed thing. Step 3 is post-processing to make that into useful information.

      Step 2 took a bit of research since most filters that don't cost more than the camera don't say anything about passing near IR or not. They just had to try a few and see which ones just happened to.

      Then, of course there's writing the code to do the post processing

      • by jythie (914043)
        Most filter manufacturers will supply you with transmission charts that go up to maybe 1000nm or so. 58mm filters (overkill for most P&S cameras already) can be pretty cheap and commonly available.
    • by Anonymous Coward

      What? How did I miss that? Pics or it didn't happen!

  • by KJSwartz (254652) on Thursday June 20, 2013 @12:39PM (#44061811)

    Similar effect - the main camera is filtered, but I've learned that the 2nd camera is not..
    Resolution may not be good, but should be adequate for proof-of-concept.

  • That you can hack digital cameras to take photographs in the infrared has been known for years... There's enough interest that you can even rent them [lensrentals.com]. (No commercial affiliation, just a satisfied customer.)

    The problem isn't the camera, the problem is the knowledge to evaluate the resulting photographs.

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