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 | ||
|---|---|---|---|---|---|
| kykytos | "Is it important the station in which the photo is taken? I mean, how do you differ infrared reflected radiation from infrared emitted radiation (th..." | Read more » | almost 9 years ago | |||
| cfastie | "Bob, this is a great idea. A secret admirer sent me one of these and I was very excited. I didn't know that any mortal could order them for only $3..." | Read more » | about 9 years ago | |||
| bobmathieson | "anyone tried the Rosco sample book... only $3.95 from adorama. The swatches will not be big enough for front lens filters on SLRs but easily big en..." | Read more » | about 9 years ago | |||
| aguchosolano | "Thanks! " | Read more » | over 9 years ago | |||
| natalie | "Yes that's correct. We have about 100 of the Infrablu filters left. After those are gone, all the new Infragrams have one each of #74, and #19. " | Read more » | over 9 years ago | |||
| warren | "Hi, aguchosolano - the Public Lab store ships internationally and will send Rosco #74 or #2007. I believe they're going to start shipping #19 as we..." | Read more » | over 9 years ago | |||
| aguchosolano | "Thanks cfastie! I am from Argentina, so I will try to contact providers that could send the filters to my country. " | Read more » | over 9 years ago | |||
| cfastie | "Theatrical gels are a good substitute for more precise filters. Rosco #19 "Fire" behaves much like Wratten 25A and costs $7.00 for a huge (20x24") ..." | Read more » | over 9 years ago | |||
| aguchosolano | "Hello! Is there any "easy to find" material that I could use to take some pictures and calculate the NDVI? I mean, before buying expensive filters ..." | Read more » | over 9 years ago | |||
| cfastie | "@camilochiang, Yes, you are correct that with a blue Rosco filter, the photo captured by the converted camera is (more or less) NGB. I think the di..." | Read more » | over 9 years ago | |||
| camilochiang | "Hi cfastie! I really think that your work is pretty awesome and for that im trying to do some experiments with the NoIR camara and your "Rosco filt..." | Read more » | over 9 years ago | |||
| natalie | " " | Read more » | over 9 years ago | |||
| natalie | "What about a different filter? Or how do we white balance these? Next Steps suggestions. " | Read more » | over 9 years ago | |||
| warren | ":-/ doesn't look good. I think without white balancing it, we're going to have a hard time using this cam. http://infragram.org/i/53f266c40ab503..." | Read more » | over 9 years ago | |||
| natalie | " The plant is dying but it still have some green to it. How is this? " | Read more » | over 9 years ago | |||
| warren | "Mathew just had trouble uploading lots of photos too, so perhaps it chokes on large uploads. If you could just upload the one raw image with a red ..." | Read more » | over 9 years ago | |||
| natalie | "I guess. What a pain in the butt. I tried for about an hour to post them at the original size and the wiki just said updating, perpetually and neve..." | Read more » | over 9 years ago | |||
| mathew | "There's an application for linux-- GUVCView that should let you capture full resolution 1200x1600) in the settings. " | Read more » | over 9 years ago | |||
| warren | "Hi, Natalie - thanks for updating, but your photos are really tiny -- is there any way you can post them at full resolution? They look promising, b..." | Read more » | over 9 years ago | |||
| natalie | "Okay check out my updates. @warren, @mathew, @cfastie " | Read more » | over 9 years ago | |||
| warren | "Here are the notes and test photos from when we originally chose the current webcam http://publiclab.org/notes/warren/09-08-2013/infragram-webcam-..." | Read more » | over 9 years ago | |||
| mathew | "white balance is tough-- I only remember control of exposure in UVC. look at these programs: http://publiclab.org/wiki/spectral-workbench-usage#We..." | Read more » | over 9 years ago | |||
| warren | "I also updated http://publiclab.org/wiki/infragram#Filters with red/blue filter information. I believe all webcams are CMOS sensors so I'm not actu..." | Read more » | over 9 years ago | |||
| warren | "The blurry photo looks interesting though... " | Read more » | over 9 years ago |