It's true if image sharpness is the criteria. For pinholes optimized for best on-axis sharpness, blur in the center of the image will be proportional to the pinhole diameter. For example, I would use a pinhole diameter of .545mm for a focal length of 240mm, (f/440). At 60mm, the diameter would be .272mm (f/220). The shorter focal length would be two stops faster. However, if both pinholes were used on 4x5 film, the sharpness of the 240mm pinhole would be fairly uniform from corner while the corners of the 60mm pinhole image would be much less sharp and much darker than the center. The reduced illimination in the corners might partly mask the increasing unsharpness. Often esthetics is more important than sharpness.
Originally Posted by waynecrider
The topic of the most desirable pinhole diameter has been debated (sometimes hotly) for well over a century. A site with ongoing discussions of pinhole photography is http://www.f295.org/Pinholeforum/forum/Blah.pl. Another site with good information is http://home.online.no/~gjon/pinhole.htm