What I want to do
Purchase an IR pass filter (blocks everything but IR light) or more ideally purchase IR pass filter sheets to be modified for my Mobius 2 camera NDVI system. I want to see if using an IR pass filter on the modified (IR filter removed) Mobius camera will help with NDVI in any way.
My attempt and results
I have not attempted this yet. I am on a fairly fixed budget (yay for being a student) and was hoping to get some input before pursuing this any farther.
Questions and next steps
I have found amazon sells glass IR pass filters for SLR cameras and I found some online retailers that sell the small filters. I am hoping someone here might be able to chime in on the pros and cons of using this in a 2 camera NDVI system.
I noticed that all the one camera systems use a filter to block certain bands of light so the NIR shows up better but never have I seen a mention of using an IR pass filter on a 2 camera system.
Would this be beneficial?
Would it make better images?
Can the current Fuji plugin be used with the IR pass filter?
Also if it is useful or worth a try what IR filter would be best for vegetation? They come in a variety of nm such as 760, 850, 950....
Why I'm interested
Just curious if this might be beneficial.
If you are going to use a single camera with the IR block filter removed, there are two options. If you can take two photos without moving the camera, one photo can be taken with an NIR pass filter (e.g., 720 nm or 750 nm) and another can be taken with an IR block filter just like the one you removed. Then the two photos of the exact same scene can be aligned and NDVI can be computed for each pixel. It might be hard or expensive to buy a 58mm IR block filter. The other option is to use a filter that blocks all blue light. The blue channel of the camera will capture only NIR, and the red channel will capture red and also NIR. The blue and red channels can be used to compute NDVI. The red channel is contaminated with NIR, but at least you don't have to align the two photos.
Another option is to use a second camera that has not been modified to get a normal photo of visible light. Use your modified camera with an NIR filter (720 or 750 nm) to take a photo of the exact same scene then align the two photos and compute NDVI with one channel from each photo.
You can use a narrow band filter to capture just pure red light (e.g., 650 nm). However, a normal camera has Bayer filters over each pixel and some of them pass only red light. So a normal camera already provides a mostly red channel (but with a much broader range and usually also some NIR). So a narrow band filter can produce better data for NDVI, but exposure times can be long and the filters are expensive.