Public Lab Research note


Testing a cheap webcam with Infragram - spoiler alert: nope

by warren | April 25, 2018 20:56 | 230 views | 3 comments | #16212 | 230 views | 3 comments | #16212 25 Apr 20:56

Read more: unstable.publiclab.org/n/16212


We've started shipping some really cheap new webcams with our introductory kits -- the imagery is not great, but we really want to ensure there's an affordable starting point, so we're offering nicer cameras at higher prices. We're doing this with the Lego spectrometer and our new Basic Microscope Kit, I wanted to see if it was possible with the Infragram project. So I gave it a try, removing the lens and substituting a lens with a red filter (turns out these webcams do use an M12 lens mount, of the same kind posted about by @MaggPi).

Here's a plant in the lobby - you can see it reflecting some blue. No white balance, but some

image description

So, over to Infragram.org and I got, using default "red filter and default colormap" -- the below image. Not good; very little highlighting of these otherwise healthy plants. It is indoor but in relatively bright "rainy day" reflected sunlight.

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It also didn't really work when I boosted the value using this instead of the standard #ndvi: `((B-R)/(B+R)+.7)`:

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So, my conclusion is that this webcam doesn't work too well for this. Maybe on a very bright sunny day it'll be worth another try...

You have to report failures too, or someone else will be doomed to repeat them! :-)


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3 Comments

Quick follow-up about another cheap webcam - this one:

https://www.amazon.com/gp/product/B01DRJXAWA/

"ELP megapixel Super Mini 720p USB Camera Module with 100degree lens" (although the other variants have the same underlying board and sensor)

It didn't work either, with not much differentiation between infrared and blue or red (tried both filters):

Screen_Shot_2018-11-07_at_9.46.43_AM.png

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IMG_20181107_100932.jpg

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It was also easily blown out by bright sunlight, which is not a good sign either -- i think it was just hypersensitive to IR.

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