Make a strip of paper and fold it in 2 with a mountain fold. You can use this to experiment with to produce “objects with reverse folds.”
A fold with a corner of 45 degrees will result in angle of 90 degrees. Two mirrored folds produce a 180 degrees combined result. You can use this to make bellow like objects, as is shown in the image above of the old camera.
Please notice that it takes four reverse folds to go all the way around. To make an object with 8 equals sides, you measure the diagonal (or calculate it) and use this as the dimension between the mirrored reverse folds.
Draw it first on a strip of paper to try. Then use the design in a pleated crease pattern.
In my example, I started with a 4 cm wide strip of paper and used a 2,82 cm distance between the reverse folds. The object was made from an a3 piece of paper.