Linear variable filters are unusual beast. One kind is linear variable bandpass filters - you can think about it as set of narrow bandpass filters distributed along the filter length.
Another kinds are linear variable short pass and a linear variable long pass filters. And you can make variable band monochromator using them
Apart from UV and IR cut, could you elaborate on some practical applications?
Well, videos show one application.
It is now state of the art, as allows to make to make very compact devices with adjustable parameters.
If you mean just bandpass filters, for example all of good spectrometers have them on linear sensor to highly reduce high order reflections from grating.
I was curious if there was some use that could cross over to video/photgraphy.
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