Nikon set the bar high when they introduced their 14-24mm F2.8 lens. This lens was so sharp that it outperformed fixed focal length lenses in the same range. But the one downside for many was the bulb front element; this bulging element made it impossible to screw on any filters. I am happy to report there is a terrific filter system for this lens, the WonderPana FreeArc system.
This setup uses a ring behind the lens hood of the lens and screws into a filter holder in front of the lens. It takes a few minutes to attach the system. You can also attach brackets to the filter holder to allow you to use graduated neutral density as well. I just returned from shooting in Acadia NP in Maine and used the filter system daily, and it worked great.
You can use both a polarizer and various graduated ND filters with the system. As many know, if you use a polarizer on a wide angle lens you get uneven polarizing (and uneven lighting) in your final shot. But if you use the polarizer to reduce glare on leaves or water, then you won’t even see this effect. I used a two stop soft edge graduated ND filter in Acadia (in the images above) and the filter helped keep my skies from being overexposed, and saturated color as well. The filter isn’t cheap, it comes in around $480. But in my book the results are worth it.