Public Lab Wiki documentation



Near-Infrared Camera

11 | 105 | | #59

The Infragram Kickstarter video, a great introduction to the project.

Introduction

Vineyards, large farms, and NASA all use near-infrared photography for assessing plant health, usually by mounting expensive sensors on airplanes and satellites. At Public Lab, we've developed a Do-It-Yourself way to take these kinds of photos, enabling us to monitor our environment through quantifiable data.

Our technique uses a modified digital camera to capture near-infrared and blue light in the same image, but in different color channels. We then post-process the image (using Infragram.org) to attempt to infer how much it is photosynthesizing. This allows us to better understand and quantify how much of the available light plants are metabolizing into sugar via photosynthesis.

You can do this yourself (as with all Public Lab tools) but there is also an Infragram DIY Filter Pack available in the Public Lab Store.

We ran a Kickstarter for a version of this camera we call the Infragram. Read more about it here » Here's the video from the Kickstarter, which offers a nice visual explanation of the technique:


What is it good for?

Multispectral or infrared/visible photography has seen a variety of applications in the decades since it was developed. We have focused on the following uses:

  • Take pictures to examine plant health in backyard gardens, farms, parks, and nearby wetlands
  • Monitor your household plants
  • Teach students about plant growth and photosynthesis
  • Create exciting science fair projects
  • Generate verifiable, open environmental data
  • Check progress of environmental restoration projects
  • Document unhealthy areas of your local ecology (for instance, algal blooms)

Notable uses include this photograph of an unidentified plume of material in the Gowanus Canal (and writeup by TechPresident) and a variety of projects at a small farm in New Hampshire at the annual iFarm event. The Louisiana Universities Marine Consortium has also collaborated with Public Lab contributors to measure wetlands loss following the Deepwater Horizon oil disaster.

Here's an example of what one of our "Infragram" cameras sees (left) and the post-processing analysis which shows photosynthetic activity, or plant health (right). This picture was taken from a commercial airplane flight:

infragram

How does it work?

Camera modification: We've worked on several different techniques, from dual camera systems to the current, single-camera technique. This involves removing the infrared-blocking filter from almost any digital camera, and adding a specific blue filter.

swap.png

This filters out the red light, and measures infrared light in its place using a piece of carefully chosen "NGB" or "infrablue" filter. Read more about the development of this technique here. You can also learn more about how digital camera image sensors detect colors at this great tutorial by Bigshot.

Post-processing: Once you take a multispectral photograph with a modified camera, you must post-process it, compositing the infrared and visible data to generate a new image which (if it works) displays healthy, photosynthetically active areas as bright regions. An in-depth article on the technique by Chris Fastie (albeit using red instead of blue for visible light) can be found here.

History of the project: While we used to use a two-camera system, research by Chris Fastie and other Public Lab contributors have led to the use of a single camera which can image in both infrared and visible light simultaneously. The Infrablue filter is just a piece of carefully chosen theater gel which was examined using a DIY spectrometer. You can use this filter to turn most webcams or cheap point-and-shoots into an infrared/visible camera.

Background: satellite infrared imaging

The study of Earth's environment from space got its start in 1972 when the first Landsat satellite was launched. The multispectral scanner it carried, like the scanners on all subsequent Landsat satellites, recorded images with both visible and near infrared light. Remote sensing "scientists" quickly learned that by combining visible and infrared data, they could reveal critical information about the health of vegetation. For example, the normalized difference vegetation index (NDVI) highlights the difference between the red and infrared wavelengths that are reflected from vegetation. Because red light is used by plants for photosynthesis but infrared light is not, NDVI allows "scientists" to estimate the amount of healthy foliage in every satellite image. Thousands of "scientists", including landscape ecologists, global change biologists, and habitat specialists have relied on these valuable satellite-based NDVI images for decades.

There are public sources of infrared photography for the US available through the Department of Agriculture -- NAIP and Vegscape -- but this imagery is not collected when, as often, or at useable scale for individuals who are managing small plots.

ndvi-vis-comparison.jpg

Caption: Normal color photo (top) and normalized difference vegetation index (NDVI) image. NDVI image was derived from two color channels in a single photo taken with a camera modified with a special infrared filter. Note that tree trunks, brown grass, and rocks have very low NDVI values because they are not photosynthetic. Healthy plants typically have NDVI values between 0.1 and 0.9. Images by Chris Fastie. Visit the gallery of high-res images by Chris Fastie


Frequently Asked Questions

Ask a question about infrared imaging

Title Author Updated Likes Comments
Infrared camera @eduardo_gamosa about 2 years ago 0
Run infragram offiline (whitout online analysis) @elucasfreitas over 2 years ago 2
Why Red filter results are blurry compared to Blue filters? @shahdharam7 almost 3 years ago 2
Can NOIR camera distinguise different types of leaf? @shahdharam7 almost 3 years ago 3
NDVI image issues from GoPro 3+ Silver @jeffa_plain about 3 years ago 9
How generate NDVI images with Infragram? @henning_leonardo over 3 years ago 1
Why the color of Infragram picture is different from what I take with my Raspberry Pi using Picamera API @iman over 3 years ago 4
Is there any correlation between Infragram, IR and Thermographic images ? @dariusjack about 4 years ago 1
How to find the sweet spot for manual white balance settings using Pi NoIR and a blue filter with artificial (full spectrum) lighting @patalbright about 4 years ago 11
NDVI Image Captures Non-Plant Objects @velahs over 4 years ago 4
Why we see red image when using blue filter? @wangmeising97 over 4 years ago 7
How should I modify Infragram NDVI settings for Raspberry Pi Noir orbital photos? @brendan_stanford over 4 years ago 9
Can I use a clear case with the Infragram pi camera? @mimiss over 4 years ago 0
Is there a way to convert an infrared video footage to NDVI? @sam14 over 4 years ago 2
Can I use the infragram.org for my thesis? Thanks! @tooooopher05 almost 5 years ago 4
How can I make IR photos derived from various cutoff useful for creating NDVI (normalized difference vegetation index) images? @lev29 almost 5 years ago 7
How to do the white-balancing for the RED filter? @xmv79667 almost 5 years ago 1
Feasibility-check: NDVI analysis of moss @zomb23 about 5 years ago 3
Bad NDVI Results from Pi NOIR with Blue Filter @nstarli about 5 years ago 6
How to design a camera for calculating ENDVI. @nickyshen0306 about 5 years ago 5
Need help to reduce the Blue in mobius point and shoot camera @Muneeswaran over 5 years ago 5
What is the working principle of Blue/Red filter @nickyshen0306 over 5 years ago 2
How do I take root and hypocotyl pictures for plant without light influence @Xing over 5 years ago 2
I just gotten my newly purchased Infragram Pi Camera, my pi.local is blank and pi.local/Cam keeps popping up message "Error in RaspiMJPEG" hence I do not get any live video feed. Anyone can help? @willieong over 5 years ago 1


How to process your images

(this section is moved to and updated at http://publiclab.org/wiki/near-infrared-imaging)

We're working on an easy process to generate composite, infrared + visible images that will reveal new details of plant health and photosynthesis. There are several approaches:

Note: Older versions of this page have been kept at the following wiki page: http://publiclab.org/wiki/near-infrared-camera-history