Since going digital people don’t seem to use filters on their lenses as much as they used to. Say you want to use a glass ND filter on your lens. First you need to remove the UV filter, more surfaces cause image degradation. But since the UV filter has been on since you bought the lens it seems to be stuck. How to get it off? The first thing is to find a roll of gaffers tape. Lay the roll on a sturdy table. Take the lens off you camera. Stand the lens on the gaffers tape with the filter end down so it is resting on the roll of tape. Grab the lens firmly and press down and turn. The filter will be slightly pressed into to stickiness of the tape to hold it in place and will have enough grip to release the filter from the lens. This might take a few tries but it will come off. Make sure how have a good grip on the lens. You don’t want it sailing across the room
This will not work if the lens has been dropped. You can email me on instructions on how to get a broken filter off, even if the glass is broken. That is not for the faint of heart, but is not hard.