This is actually a test shot of filter holder. I borrowed my friend's Lee Holder + 105mm Heliopan CPL, and Wide Angle Lens adapter to compare with my Cokin Z-Pro holder setup. It turned out having obvious vignetting at 17mm. (I don't have such problem with my slightly modified Z-PRO systems). Instead of eliminating vignetting, I did it the other way around -- giving it much more vignetting in Photoshop.
And yes, it was raining.