I thought I would class the various optical filters I own and use into 5 different groups. I do own many different other UV-pass filters of different thicknesses, but have not included them here. These include: Schott UG1, UG5, UG11, BG3, Hoya U360 and B+W 403.
As can be seen in the pictures below, I have adapted some of the smaller filters to 49mm filter size, so as to use them with my Xume magnetic adapters for easy changing of filters when shooting with them.
The 330AF20 lets through 320 to 340nm bandwidth, and is good for testing the transmission of lenses, or for seeing what a flower looks like in that spectrum of light.
For IR-cut, I tend to use the Baader UV/IR cut filter as it is the most effective in blocking UV & IR, which makes it particularly suited for UV-induced visible fluorescence (UVIVF). The Olympus internal cut filter (ICF) does let through a small amount of UV, so is not as useful for UVIVF. BG40 will give a closer white balance to the ICF than the other filters.
My favourite infrared filter is the RG665 (although not as readily available as the others and costs more) as it gives a slightly more colourful infrared image due to the light spectrum it lets through which includes a little red as well.
I have been using the Astronomik CLS-CCD filter as it is said to be the best at blocking skyglow for astrophotography. I do own the Baader Neodymium filter which is said to be great for lunar and planetary visual work and for imaging, but I have yet to try this – but hopefully will have a chance to do so real soon once my astronomy setup is completed.
I have seen some work on the net using the Baader Neodymium filter for imaging deep sky objects as well, so I will try that as well and compare it with the Astronomik CLS-CCD filter. I do own Kson O-III and UHC filters in both 1.25″ and 2″ sizes. I had previously bought a pair of each in 1.25″ size for binoviewing, but have since sold on my Denkmeier binoviewer. I have only photographed the 2″ filters in the photo below.
These filters are ones I have bought to do specific types of imaging. The 325BP10 is a narrowband filter to test how deep a lens transmits UV; unfortunately it did come with aberrations to its dichroic coating, which I have had to black-out with a sharpie to reduce the light-leak.
The Insect-D-sight 1 & 2e (IDS1 & IDS2e) filters were developed to pass UV and some blue/green, while blocking red and infrared, to mimic the light spectrum that certain insects see in. I find these filters very interesting, as they can reveal something about flowers which were otherwise UV-dark.
As you can see, there are so many different filters out there and different types of imaging that can be done with them. But clearly some of these filters will require a camera which has been modified by removing its internal cut filter (e.g. UV-imaging, IR and even astrophotography), in order for the sensor to be able to capture the invisible light spectrum.