For those that like real experimental work, this 6 x 9 ( 8 on 120) pinhole diy camera was designed to provide apertures from f 75 to f 416.  There is little point in trying apertures smaller than f 416,  since diffraction  will then control the resolution, not the f number. The user manual for this  camera may be viewed on  the documents page.

 

diy cameras P8