Hi everyone, I have started experimenting with long-time exposures, and would like to use a filter system that would not cause vignetting with the following equipment: - full frame camera - 20 mm focal length - 72 mm diameter filter thread I would like to put at least 2 but preferably 3 different filters in front of the lens (polarized + natural grey + graduated grey). Is there a filter holder/system that would make it possible without vignetting? I currently use Cokin (I think this is "Cokin P", but I am not sure), and it holds 3 filters very well, but the holding frame is clearly visible even when I frame the picture before taking, not to mention the final image. I've been trying to hold the filters by hand in front of the lens, but it becomes very difficult with exposures of several minutes and above. Any advice would be appreciated.