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Infragram Filters

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The Infragram project has used a variety of filters to make Do-It-Yourself infrared cameras, as well as infrared-visible multispectral cameras. This page is about choosing filters for different purposes.

Red vs Blue

Both blue and red filters are intended to block most visible light in one channel, to then use that channel for near-infrared light. This way, a single camera can be used to take simultaneous visible light and near-infrared light photos -- one in the red channel, one in the blue channel (we discard the green channel).

Most recent DIY efforts on Public Lab have focused on red filters, but early on we used blue filters. A red filter (the most common conversion we see on Public Lab as of October 2017) results in vegetation appearing pale blue, and a blue filter typically results in vegetation appearing pale yellow.

Left: pale blue from a RED filter; Right: pale yellow from a BLUE filter. Images by @mathew and Eclectis students

Background on filter choice

There's a lot of research about this choice here:

Title Author Updated Likes
How to calibrate the white-balance for NDVI using the BLUE filter? @cagiva 3 months ago
Red vs. blue filters for NDVI @nedhorning 11 months ago
Can I use any red filter for capturing NIR light? @sujayj about 2 years ago
Plant Health NDVI Consumer camera vs Professional multispectral camera @Claytonb almost 3 years ago
Plant health NDVI Red vs Blue filter @Claytonb about 3 years ago
Why a red filter should work well for NDVI @nedhorning over 5 years ago

Filter sources

We've been using Rosco theater gels as filters, and we currently carry the red Rosco Fire # 19 in the Public Lab store

Red filters include:

  • Rosco Fire # 19

Blue filters include:

  • Rosco # 2007
  • Rosco # 87

Also see this research on various Rosco filters:

Title Author Updated Likes
Artichoke filter search @cfastie 8 months ago
Hacked Infragram Raspberry Pi camera now on the International Space Station @warren about 1 year ago
NIR, Rosco fire #19 and my elph 300HS from Christmas @admaltais over 3 years ago
Video streaming with infragram on intel edison (ubilinux) @pjsbill about 4 years ago
Canon SD4000IS as Infragram @warren over 4 years ago
Announcing the Infragram Point & Shoot @mathew almost 5 years ago
A Wratten 25A replacement from Rosco? @mathew almost 5 years ago
NDVI with Canon A2300, APM Hexacopter DJI550, Help @andresc4 about 5 years ago
A490 Rosco 2007 initial results @patcoyle almost 6 years ago
NDVI from Infrablue @cfastie almost 6 years ago
Infrafilters @cfastie almost 6 years ago
Middlebury Meetup @cfastie almost 6 years ago
Rosco! @cfastie almost 6 years ago
Superblue @cfastie about 6 years ago
Show more

And the Rosco website:

And an article on the history of Rosco filters:

Exposed negative film

To make a camera take only near-infrared photos, you can use a piece of exposed negative film as a filter. This will block most visible light (since the red, green, and blue channels are blocked) but will allow infrared light.

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