wide angle lens and filters

[CRman]

My tokina 12-24 I have rarely gotten to use. I have upcoming trips where it will be handy. I did buy a slim mount multi coat CP for it. How important and at what focal length does it matter if you use a slim mount filter. I need a few NDs a grad ND and misc. filters. I have found the focal length I use the most to be 15-17mm.. I am worried when I need 12-14. Mainly landscape and waterfallfs as you may imagine. Thanks in advance.

Marc

 

[Mav]

Ken has you covered.