My first post on the Holga 120 WPC (Wide Pinhole Camera) was done using the 6x9 cm mask. Now I have developed a roll I shot on a walk about in San Jose using the 6x12 cm mask. The first thing that is noticeable about this wider mask is that there is some mechanical vignetting apparent in the photos. Also, the vignette is asymmetrical with the right side being more pronounced than the left hand side.
Compared to the 6x9 cm mask, I think I prefer the wider format of this mask so that is what I'll be leaving in the camera for now.
You can see my original review of the Holga 120 WPC (Wide Pinhole Camera) in this post.