well I have a tokina 12-24 and when I mount a cokin P set on the end, you can see the flter housing on the sides, left and right.. If you flip the camera vertical, and rotate the cokin, the edges dissappear... has anyone ever tried to cut down the width of a cokin P holder?
I did. It works on 12mm. But you cannot rotate the holder at all @12mm. Moreover, there's a chance to get "a little" vignette, since the upper part of the holder is thicker.
If you are on the budget, or you don't wanna go for X-series, cutting the width of P-series holder is great.
I took this photo with Tokina 12-24mm @16mm and Grad ND on. I rotate the holder, which is for P-series, to match the slanted building line.