Turn a Canon Camera Into a Plant Health Analyzer Using Public Lab's DIY Infragram

The "Infragram" project is a near-infrared imaging platform developed by the Public Lab community.   In this Instructable, we'll show you how you can use a cheap filter (available through Public Lab's recent Kickstarter) in order to modify an inexpensive point & shoot camera, turning it into a device capable of capturing capture "NDVI" imagery -- the same technology that NASA and farmers currently use to assess plant health.

This how-to focuses on a camera that is particularly easy to source and modify: the Canon A495 (the instructions will be identical for the A490).  You can buy a used version of this camera for around $50 or less on Amazon or Ebay.  

The main steps we'll need to accomplish are: a) remove the near-infrared blocking filter from in front of the camera's sensor, and b) add on a cheap "red-blocking" filter. 

Tools:

- A Canon A495 or A490
- A small phillips-head screwdriver
- A small strip of tape (most any type will do)
- A piece of Rosco #2007 filter paper (available from Public Lab right now via their Kickstarter, for $10)

Note:  if you'd rather not modify your own camera, Public Lab is also going to be producing a pre-assembled "point and shoot" camera -- you can sign up to get one by supporting their Kickstarter. 

Also note: this material is also explained very nicely in a Public Lab how-to video -- it'll be very useful to watch that video once before starting, and to use it as an accompanying guide for this Instructable. 

Warnings before you begin:

#1: There is a capacitor located deep inside the case of the camera.  Don't stick the screwdriver in random crevices of the camera -- you could receive a bad shock!

#2: It is very possible to ruin your camera's functionality by making a small mistake.  Don't do this with a camera that you'd really miss if something goes wrong ...

Okay, if you're ready  to modify your own Canon A495/0, let's begin!

First, you'll need to remove the batteries from the camera.

(But keep them handy -- you'll be using them again later.)

There are five screws on the outside of the case.
Using the phillips-head screwdriver, remove each one, setting them aside for safekeeping -- you'll need them again later when re-assembling the case.

Note: two of the screws are located under the rubber flap that protects the USB port; and another screw is located inside the battery compartment.

If you can't find all 5 on your own, hopefully the photos I'm including here will help you locate them.

Tip: use a piece of tape to hold the screws nicely in place on the table you're using -- you can place the screws on the tape in the order in which you removed them (and even label them), so that you won't forget which screw goes where.

All of the screws on the outside of the case are interchangeable, but they are different from the screw we'll be removing next -- so set them apart and remember that they're 'external' screws.

Next, you'll need to pull apart the external camera case.  We've found that it's particularly convenient to use your fingernails right next to the external speaker location.

Pull the case apart gently.  

You'll end up with three pieces: 
- the "back" of the camera, with a window that covered the LCD
- the "front" of the camera, which contains all of the electronics
- the battery compartment cover, which will just simply come off as you pull the case apart.

You'll need to remove three screws.

These are a different size than the "external" screws you removed on the outside of the case, so make sure to keep them separate and secure for re-assembly later.

The blue material in this picture contains the buttons you use to interact with the camera.  It is connected to the main circuit board of the camera via two "ribbon cables" -- little tabs that contain lots of fine wires.  In order to be able to reach the camera's sensor, we need to disconnect one of these ribbon cable tabs -- the one on the "bottom right" of the camera (shown).  

The best way to accomplish this is by sliding the shaft of a thin screwdriver right underneath the ribbon cable tab, between the tab and the rest of the camera.  You can then use the screwdriver to pull the ribbon cable out of its "socket".

Be gentle!

Now we want to be able to get the LCD display out of our way (the sensor is underneath it).

First you'll need to flip up the blue button pad.  Now that you've unplugged one of its ribbon cables (in the previous step), the other ribbon cable will act as a "hinge", allowing it to be flipped up out of the way.  

Now that you're holding the button pad out of the way, you can also flip the LCD display over.  You'll need to "undo" a little metal latch on one side of the LCD display (use the tip of a screwdriver to press the latch inwards, releasing the mechanism).  

Again -- be gentle!

Now you can see the circuit board of the camera, as well as what I'll call the "sensor assembly".  There are three screws on the sensor assembly that you'll need to remove.

Unfortunately, sometimes there is a little glue applied to these screws by the manufacturer to keep them in place.  You may need to scrape the glue off -- but be very careful not to leave glue bits inside the camera!

If you're keeping track of the screws you've removed (e.g. by placing them on a strip of tape, as suggested earlier), you'll now have three sets of screws: a set for the exterior, a set for the LCD (which I'm labeling "interior" in my photo), and a set that was around the sensor.

This is the trickest part -- it's very easy to damage the sensor in this step, so be very careful!  Also, try very hard not to allow any dust or other materials to fall on the sensor during this step.

Using your screwdriver, flip up the sensor cover assembly, as shown.  

You'll reveal the sensor, surrounded by a rubber gasket.  

Lifting up the rubber gasket a bit (but trying not to remove it), turn the camera on its side and shake out the infrared block filter.  It is a small, rectangular piece that looks like blue-tinted glass.  

Keep the filter in case you find another project for which it might come in handy!

As soon as the filter pops out, allow the sensor cover assembly to fall back into place, protecting the sensor.

It might take some jiggling to get the cover back in place; just be patient, and allow it to settle nicely back into its original location.

Then replace the screws you'd removed earlier.

Careful not to drop the screws inside the camera case!

If everything went well, now we can begin the process of re-assembling the camera. 

Flip the LCD assembly back over, and then replace the button pad atop it (there's a little metal tab to fix the button pad in place -- make sure you fit the button pad over that).

It's a bit tricky to get the button pad ribbon cable re-inserted in its socket -- be very careful not to 'crease' the ribbon cable while doing so, as you may break the tiny wires in the cable.  With some gentle wiggling and pressing, it should eventually go in (and needs to go in rather 'solidly' in order to make a connection).  

Now is a good time to test to see whether the camera still works -- if it doesn't, it'll be easier to just go back a couple of steps and make sure that e.g. that you plugged in the ribbon cable well enough (I myself hadn't, and was able to fix that relatively easily). 

Turn on the camera.  The lens should extend, and the LCD should light up.  Test the focus.  Hopefully everything works!  If not, retrace your steps a bit; making sure that everything is in order.  

Basically, you're now ready to finish re-assembling the camera, following the earliest steps of this Instructable in reverse order.  

1. Replace all of the LCD housing screws (the ones I labeled "interior" on my screw-tape collection)
2. Re-connect the battery door
3. Fit the case back together.  You'll need to be gentle when doing this, and make sure that all of the little plastic and metal tabs around the edges of the case fit together nicely.  It'll require a bit of wiggling -- just be patient.
4. Replace the "external" screws that hold the case together.

Now, you've finished turning your Canon into a "near-infrared imaging device"!  The "red" channel on the camera's sensor is now taking in both "red" and "near infrared" light.

The final step is to add an "infrablue" filter that blocks incoming visible red light -- this way, the "red" channel on the cameras sensor will only register near-infrared light, allowing us to compare the amount of infrared light the camera sensor sees with the amount of blue light it sees (this is what's needed to generate NDVI plant health imagery).

A useful filter to use (which might also be the final filter included in Public Lab's kit) is a "Rosco #2007" filter, which nicely blocks incoming red light.

Cut a small square of the filter material, just big enough to cover the camera's lens, and secure it with small pieces of tape. 

Now you can start to use your new "plant health tool" to take pictures of plants!

Public Lab is developing an online "infragram photo developing platform", currently located at http://infrapix.pvos.org (the location may change -- check the Public Lab's infragram material on their website for the latest location).  

Please do start to capture images with your new near-infrared camera, develop them,  ask questions, and give feedback and contribute to development via the Public Lab Google Group. 

Enjoy!