A very nice ultrawide pinhole camera from James Guerin at aupremierplan.

Here is his description the loading of this camera:

Curved film plane?

The film plane is curved to ensure even exposure across the negative, not possible with a flat film plane with such an extreme wide angle view (141° angle view of equates to a focal length of 6.4mm in 35mm terms). T

A side-effect of the curved film plane is that it results in a curved horizon in your photos unless the photo is taken with the camera level.  This is why a precise bubble level features on the top plate of the camera.

Camera features

• CNC machined body
• Curved film plane with a radius of 70mm (focal length).
• Large 6x17cm (57x170mm) negative giving 4 shots per roll of film (120 roll film).
• Angle of view: 141 degrees horizontal, 44 degrees vertical.
• Laser drilled 300 micron (0.3mm) pinholes (f/233). Pinhole material thickness = 50 microns (.002″).
• Magnetic shutter
• Dual pinhole allows horizon to be placed on upper or lower third (camera level)
• Accurate aiming lines for composition.
• Precise bubble level.
• Standard 1/4-20 tripod mount socket
• Rubber feet
• Film spool tensioner at take up spool