I agree with Ernie that filters are largely obsolete.
I keep high quality clear glass protective "filters" on all of my lenses except for the "great white primes" which mostly have sacrficial front elements (at least compared to the cost of the rest of the lens) and have far too large front elements to use a front filter.
The only time you really might need a filter now is a neutral density type if you want to shoot wide open with a fast lens in bright lighting (i.e. shallow DoF) and you either need to use a lower shutter speed or the amount of light takes you outside the available exposure triangle at your greatest shutter speed but that is a pretty rare set of circumstances for most people.
I've thus far been disappointed by how wimpy the red, yellow and orange software filters have been for my B&Ws. I recall the olden-day glass filters to have been more efficacious, particularlly the red.
Any opinions on this?
Nearly every digital image sensor assembly contains a UV filter, so you can scratch those off the list. I have found CPL filters can wreak havoc with some AF Phase Detect systems because CPL filters work by "normalizing" the light, which removes most phase information.
ND filters are more useful shooting video than stills.I can add background blur in Photoshop, so I really do not need to shoot stills at f/1.2 in bright sunshine.
However, video shutter speeds tend to be MUCH slower compared to stills. Using an ND filter is almost mandatory if you want any sort of OOF background. Also, using a variable ND filter is a good way to control exposure when shooting video, instead of changing camera exposure settings.
As for colored filters, that is definitely something that most software can easily handle. I do not know what software you are using, but PS can do almost anything you might need in that direction.
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