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 | ||
|---|---|---|---|---|---|
| sujayj | "Thanks Chris " | Read more » | about 7 years ago | |||
| cfastie | "You can use any filter that blocks most blue and green light (all visible light other than red) and also passes a lot of near infrared light (somew..." | Read more » | about 7 years ago | |||
| LaPa | "I'm happy for this my first step in NIR and NDVI photograph! Maybe you know but ..... 1) I use not a real camera but a computer board (Raspberry Pi..." | Read more » | about 8 years ago | |||
| cfastie | "That looks pretty good. With the defaults in the photo monitoring plugin, the plant leaves have an NDVI value around 0.3. We don't know what the ND..." | Read more » | about 8 years ago | |||
| LaPa | "HI, What do you think about my last test? NoIR modulo cam+blue filter, WBgain red = 0.88 and WBgain blue = 0.57 " | Read more » | about 8 years ago | |||
| LaPa | "I'll try to get blue > 30 and red < 200 changing the gain. At the moment I do not know how change the exposure. May be I have to read better ..." | Read more » | about 8 years ago | |||
| cfastie | "Here is the range of NIR:VIS ratios for NDVI values between 0.2 and 0.8. " | Read more » | about 8 years ago | |||
| cfastie | "That looks promising. I guess that PiCamera module is a useful tool. I think that photo is a little too yellow. The blue values for foliage are ver..." | Read more » | about 8 years ago | |||
| LaPa | "Hi, I'm here again! I shoot a set of pictures by NoIR modulo cam and blue filter. I tryed finally different white balance. The photo that I post i..." | Read more » | about 8 years ago | |||
| cfastie | "The Bayer filters determine how wavelengths are separated into the three color channels. This is how the camera can sense the balance between the t..." | Read more » | over 8 years ago | |||
| poo | "this green photo don't Relevance to Bayer pattern Mr. @cfastie ? " | Read more » | over 8 years ago | |||
| cfastie | "Black surfaces do not reflect much light, but they do reflect some. Some black surfaces might reflect more green than other colors, and other black..." | Read more » | over 8 years ago | |||
| poo | "hi. I have a question. when I set a black paper or black thing in custom white balance, and then i take a photo, why my photo become a green photo?..." | Read more » | over 8 years ago | |||
| LaPa | "ok, i have to solve some problems of remote link of the Raspberry before taking other photos. And, of course, I have to buy a red filter because th..." | Read more » | over 8 years ago | |||
| cfastie | "LaPa, yes that would be very useful. It would also be useful if someone could do that with a red filter on the NoIR. Blue should be exaggerated whe..." | Read more » | over 8 years ago | |||
| LaPa | "Hi Chris thank you for the suggestions! Do you think would it be a good idea take a set of photos (NoIR camera + blue filter) of the plant graduall..." | Read more » | over 8 years ago | |||
| cfastie | "Those basil leaves should not be the same color as the flower pot. They need to be more orange. To get NDVI values in the appropriate range, the va..." | Read more » | over 8 years ago | |||
| LaPa | "At the moment I took a photo two plants in sunny light. But I didn't manage to take another without gain because it became cloudy :(. Is it possib..." | Read more » | over 8 years ago | |||
| LaPa | "Thank you cfastie, I seem that your post encourages me to keep on this way; I ask confirmation about this. Do you have any idea how to modify the p..." | Read more » | over 8 years ago | |||
| cfastie | "That orange color of the leaves is promising. It should be even oranger. If you can put the plant in brighter outdoor light and take two photos -- ..." | Read more » | over 8 years ago | |||
| LaPa | "anyway I try awbg. I wrote in the terminal "raspistill -awb off -awbg 0.88,0.97 and I took a picture of the tester and a two plants. The light was ..." | Read more » | over 8 years ago | |||
| LaPa | "Actually I don't know if it is possible mount two modulo cam in 1 Raspberry because it has just 1 slot to mount a modulo cam. I'll find out more ab..." | Read more » | over 8 years ago | |||
| cfastie | "It is not clear that the other respondents at the Pi forum understand what you are asking about. Using awb_gains will allow every photo to exaggera..." | Read more » | over 8 years ago | |||
| LaPa | "What do you think about this way to proceed? https://www.raspberrypi.org/forums/viewtopic.php?p=856005#p856005 " | Read more » | over 8 years ago |