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.

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## 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](https://publiclab.org/n/9372)_

[![](/system/images/photos/000/018/533/thumb/Rosco_26_filtered.JPG)(/system/images/photos/000/018/533/original/Rosco_26_filtered.JPG) [![](https://i.publiclab.org/system/images/photos/000/001/647/thumb/IMG_0025.JPG)](https://i.publiclab.org/system/images/photos/000/001/647/original/IMG_0025.JPG)

### Background on filter choice

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

[notes:red-vs-blue]

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## 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](https://store.publiclab.org/collections/diy-infrared-photography)

Red filters include:

* Rosco Fire # 19

Blue filters include:

* Rosco # 2007
* Rosco # 87


Also see this research on various Rosco filters:

[notes:rosco]

And the Rosco website: http://us.rosco.com/en

And an article on the history of Rosco filters: http://www.rosco.com/spectrum/index.php/2016/11/decoding-the-language-of-color/


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## 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.