Okay, continue to search for filters. This time, IR pass. Guess what, I was able to find the a good IR pass filter from the same website.
20161223/http://www.pmoptics.com/filters.html
20161223/http://www.pmoptics.com/ir_filters.html
Okay, but what about UV pass filters? Judging from the text of the website above, I should just search for “UV filters,” apparently.
Oh wait, I should search for “UV pass filters.” Yeah, I think that should provide for broader results in my specific category of search.
20161223/https://en.wikipedia.org/wiki/UV_filters
Oh, but interesting. I’ve learned that sunscreens are a new class of environmental pollutants. One of the main problems is that wastewater treatment facilities are (for the most part) not capable of filtering out sunscreens from waste water.
20161223/http://www.globalspec.com/industrial-directory/uv_pass_filters
Those filters are too big. And, despite the IEEE logo, I think the selection of products is too limited.
20161223/http://www.naturfotograf.com/UV_IR_rev04.html
Oh hey! Maybe I should search for “UV band-pass filters.” Or maybe “UV band-pass filter.”
20161223/UV band-pass filter
Okay, so you were asking this question, so I shall tell you the answer. Should I go for three different filters that subtract one of the possible three undesired wavelength ranges? Then, for viewing, I would stack two of the three filters together. Or, should I buy three filters that subtract the other two wavelength ranges but pass the desired range? That way, I would only need to place one filter in front of the camera. It turns out that the method that subtracts two-out-of-three is likely better, as I have seen the graph of the filter efficiency, and the bounds are not “square.” Rather, the filter strength fades off gradually as the wavelength changes. So, it is likely better to go with the ones that filter the larger ranges, as we will likely get better quality with that method.
Wait, wait, upon further analysis of the URL above, from naturfotograf.com, I’ve been told that you need a Quartz lens for good ultraviolet photography. So, now I’m wondering. What’s the UV light performance of a plastic lens?
20161224/DuckDuckGo uv light plastic lenses
20161224/http://www.laramyk.com/resources/education/lens-options-and-materials/the-problem-with-uv-400-treatments/
Unfortunately, the results are somewhat dismal. A plastic lens absorbs 75% of ultraviolet light, and often times, there are UV absorption additives put in the plastic lenses to prevent them from yellowing from contact with ultraviolet light. This is in addition to the problem of there generally being only a very low level of UV light in outdoor environments, further complicating the matter of UV photography by requiring long exposures with even good lenses for UV. So, in other words, although it may be possible to get some UV photographs out of the Raspberry Pi NoIR camera, you really shouldn’t count on getting good quality photographs out of such a setup. As a matter of fact, as far as I am concerned, if I can’t get good photographs out of a certain spectrum, I might as well not try to take any photographs at all in that spectrum. So, that’s the end of UV photography with the Raspberry Pi NoIR camera. If I’m going to end up taking off the plastic lens and using my own lenses instead, I might as well hold off until I can do so with a DSLR camera, which will give me better results for an interchangable lens setup anyways.
So, I’m calling off the search for filters that block infrared and visible light but not UV light. However, this is where I last left off. I’ve found some interesting resources and the link below may give me some more hints as to what keywords to type in to search for the correct filters.
20161223/https://www.newport.com/f/bandpass-filters
20161223/https://www.newport.com/f/visible-absorbing-bandpass-filters