Late last year we released our first version NDVI converted cameras using Schott BG3 filters. Using those filters we were able to generate pseudo NDVI images with a single camera, building off the work of the Public Lab project. After working with faculty at the University of Boston and the MEASA Lab at KSU, we determined that we weren’t quite getting the best results possible with the BG3 filter glass. Unfortunately, no off the shelf filter glass seemed to do exactly what we needed, block out red light and allow NIR light to pass instead. Luckily, we were able to find a manufacturer to help us build a custom filter to our specifications, and the results are looking really good! Below are two images, the first taken by a camera with BG3 filter glass and the second taken by a camera with the new custom glass, the difference is clear.
Aside from higher overall values, there is more differentiation and detail in the leaves and a larger difference compared to the non-organic background material. This is especially important for this type of camera. Since these are uncalibrated, pseudo NDVI images, what is really needed most is high differentiation so that comparisons can be made between the majority of plants and potential problem areas. The higher detail available now makes it possible to catch unhealthy plants sooner.
The new filters will be priced at $39.99 for the filter alone (8.9×7.9mm, fits SX260 and S100 at least) and $499.90 for a ready to go converted SX260 with CHDK. It’s a little cold to be doing any crop surveys here in the Northeastern US right now, I actually ended up killing those two plants after taking them outside for just a few seconds! We’ll be out and collecting imagery as soon as anything starts growing and I’ll post updates as they become available.
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