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](https://publiclab.org/n/9372)_ [(/system/images/photos/000/018/533/original/Rosco_26_filtered.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] **** ## 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/ **** ## 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. ...
| Author | Comment | Last activity | Moderation | ||
|---|---|---|---|---|---|
| warren | "Hi natalie- it looks like the focus is a bit off... You actually don't have to remove the lens or anything to test this, you can just tape some red..." | Read more » | over 9 years ago | |||
| cfastie | "kykytos, This is a really good question. Lots of blue light can pass through a #2007 filter, so a white light viewed through the filter will appear..." | Read more » | over 10 years ago | |||
| kykytos | "Hi, I don't understand how can be blue color the Rosco #2007 VS Blue filter when it allows blue light to pass. We see the color of the objects beca..." | Read more » | over 10 years ago | |||
| warren | "BTW, this post is now the 7th most popular research note (by view count) on the site! " | Read more » | almost 11 years ago | |||
| cfastie | "Hi jalarid, Yes that is correct. There is lots of active development about which cameras and filters work best, and how to get the most meaningful ..." | Read more » | almost 11 years ago | |||
| warren | "That's right, jalarid! " | Read more » | almost 11 years ago | |||
| jalarid | "Hi, so if I am understanding this correctly I only need to remove the IR filter from my camera and replace it with Rosco #2007 VS Blue filter. At t..." | Read more » | almost 11 years ago | |||
| mathew | "kykytos-- I put Chris out of the filter business . If you are interested in helping us do research on filters, please e-mail me. mathew at publiclab " | Read more » | almost 11 years ago | |||
| cfastie | "kykytos, Sorry, I am out of the business of mailing #2007 filter. We are currently testing several different filters with different cameras to choo..." | Read more » | almost 11 years ago | |||
| kykytos | "I'd like some of the Rosco filter too. Thanks! " | Read more » | almost 11 years ago | |||
| cfastie | "Hi jaluna, NDVI tells us something about plant health because it quantifies the difference between light that is absorbed by plant pigments and use..." | Read more » | almost 11 years ago | |||
| jaluna | "Hello cfastie! I follow your job with interest, but there are a thing that I not understand well. You say "A filter can be used to block all red l..." | Read more » | almost 11 years ago | |||
| nedhorning | "I have a feeling it is a white balance problem. The blue channel seems to be off. I would expect vegetation to be much darker in the blue channel. ..." | Read more » | almost 11 years ago | |||
| cfastie | "Can I do a better post-white-balancing to recover useful data? If you adjust the white balance on the infrablue photo, or make any other changes t..." | Read more » | almost 11 years ago | |||
| cfastie | "The Rosco 2008 should be one of the best filters for making NDVI because it blocks all the red light better than others. It has only 40% of the ove..." | Read more » | almost 11 years ago | |||
| cfastie | "Jeff, do you have an image of the lut you used? You can open a lut in Fiji by file/open. " | Read more » | almost 11 years ago | |||
| liz | "@Jeff i really like this NDVI color gradient that replaces violet with black. " | Read more » | almost 11 years ago | |||
| cfastie | "This set has the Rosco and the halogen. https://spectralworkbench.org/sets/show/366 " | Read more » | almost 11 years ago | |||
| warren | "Can you link to the spectra so I can give it a try? Thanks. " | Read more » | almost 11 years ago | |||
| cfastie | "Jeff, Your first question: I subtracted the Rosco spectrum from the halogen light spectrum, but the result made no sense at all. So I just used the..." | Read more » | almost 11 years ago | |||
| warren | "I've been modifying lots of cameras with the new superblue filter (using the Rosco filter you sent). For those (like webcams) which don't have cust..." | Read more » | almost 11 years ago | |||
| warren | "Apparently, from my phone, not nearly well enough. There are disadvantages to a mobile friendly website... Using baseline subtraction in Spectral ..." | Read more » | almost 11 years ago | |||
| cfastie | "That's an excellent color table for the heat metaphor. This topic of how to display NDVI deserves much more attention. "It'd be neat to test the r..." | Read more » | almost 11 years ago | |||
| warren | "I've been messing with different NDVI gradients, and have been trying to get one which shows "cool" colors below zero, and doesn't circle back arou..." | Read more » | almost 11 years ago |