Slashdot Mirror

← Back to Stories (view on slashdot.org)

Homebrew Camera Mod Mimics LANDSAT Satellite

Posted by timothy on 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.)

21 comments

  1. Infrared filter? by Anonymous Coward · · Score: 2, Insightful

    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.

    1. Re:Infrared filter? by Anonymous Coward · · Score: 4, Informative

      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

    2. Re:Infrared filter? by sjames · · Score: 2

      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.

    3. Re:Infrared filter? by Anonymous Coward · · Score: 1

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

    4. Re:Infrared filter? by Anonymous Coward · · Score: 0

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

      All 20 lines of MATLAB/Octave code!

    5. Re:Infrared filter? by skgstyle · · Score: 1

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

    6. Re:Infrared filter? by sjames · · Score: 2

      If it could be ANY 20 lines of code, it would be trivial. Alas, it needs to be the correct 20 lines or the results are worthless. Which 20 lines are useful is a matter of understanding, educated guesses and trial and error.

    7. Re:Infrared filter? by Lumpy · · Score: 2

      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.

      --
      Do not look at laser with remaining good eye.
    8. Re:Infrared filter? by tgd · · Score: 1

      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, fancy, creative or whatever about this. There are literally a hundred sites about doing digital camera conversions and all the stuff you can do with full spectrum cameras.

    9. Re:Infrared filter? by tgd · · Score: 1

      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.

    10. Re:Infrared filter? by Anonymous Coward · · Score: 0

      And this is why no one wants to use perl for programming. Because no matter what you do, someone will respond on the internet with "but it is only one line of perl code."

    11. Re:Infrared filter? by skgstyle · · Score: 1

      Maybe you are thinking of UV filters? I was referring to lens filters like this - http://www.adorama.com/HY58RM72.html which only allow infrared rays above 720nm to pass through the glass.

    12. Re:Infrared filter? by jythie · · Score: 2

      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 grade filters one would use for professional or scientific work.

      That being said I am in favor of projects that let people play with exotic photography on a budget.

    13. Re:Infrared filter? by jythie · · Score: 1

      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.

    14. Re:Infrared filter? by Obfuscant · · Score: 1

      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 on the use?

      Its easy to remove the IR/UV filters in a camera...

      Not if the filter is built into the sensor, it isn't. That's why they don't build them into the sensor. If it's easy to remove the filters in the sensor, I challenge you to remove the Bayer filters from a color sensor and turn the camera into true monochrome.

      But you're right, this stuff isn't new simply because it is so easy to take the filters out of the camera. I've had mono cameras I've had to put IR filters in because the vendor didn't (but does for the same model in color because without it the colors are off.) I've got one on my desk now that has no IR filters but does have an IR pass, and the images are very, well, they look funny if you don't know what is happening.

  2. Why not use iPhone 4/4S Facetime Camera by KJSwartz · · Score: 3, Interesting

    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.

  3. Isn't re-discovery great? by DerekLyons · · Score: 1

    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. (No commercial affiliation, just a satisfied customer.)

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

  4. DIY? by Anonymous Coward · · Score: 0

    "Public Lab is an open community supported by a nonprofit?"

    Really, we are starting to call anything corporate funded, DIY. Next thing you know is DIYers need some community backing to do anything and be spotlighted.

    LIRC a DIYer, homebrew thing was a self supported, self promoted (but known virally through social sites), and truly done in a garage, truly viral in support.

    This looks like non-profit funded, academically supported project repackaged as a "DIY bedroom" project. It's not DIY, unless we are now calling stuff like university projects (with millions of $$ of funds) as DIY. Just a bunch of smart hackers who chose not to go the corporate job route...

  5. NDVI capabilities? by Anonymous Coward · · Score: 0

    This project reports to allow for NDVI calculation, yet removes the red band from the camera. Can someone explain how this could possibly work? NDVI is calculated as (NIR - Red)/(NIR + Red). The red band is used because chlorophyll's absorption peaks are red (780 & 800nm).