Greg asked > > So, does the light falloff of a pinhole camera image follow an inverse square > > rule? Will it always be an issue no matter how big your shoebox, cigar tube > > or Quaker Oats box is? Andy answered: > I believe the answer is YES. And Guy continues: In fact, the rule of thumb is that the maximum useful image circle is 3.5 times the focal length - that is 3.5 times pinhole-to-film distance. Because of the various factors mentionned by Andy. Of course, the light fall-off is only a problem with wide-angle, and it gets less (more) and less (more) a problem as the angle of view is narrowed (increased). If you create an image with a normal or telephoto angle of view, the light fall-off will be minimal. But then, the increase in focal length with reduce you effective aperture and increase exposure time overall. This could quickly become unmanageable, especially when you factor in reciprocity failure problems... In the case of the hotel-room-turned-into-pinhole-camera picture, I wanted to have a wide perspective and experienced a lot of light fall-off on the edges (actually this also can also be stated as experiencing a lot of over-exposure in the center). With trial and error method, I discovered that the best way to handle this is to do in-camera dodging at the center of the image by one or two stops. This is fairly easy to do and we did it with good results (but not enough vigour) in the second set of giant pinhole pictures I produced a couple of months ago. http://pages.infinit.net/memfloue/wilder.htm This is something which Vera Lutter in New York does regularly with her own giant pinhole work. In fact, she seems to have developped a tremendous control over this procedure, by the looks of the paper negatives she shows on the walls of galeries or in her book. Now what do you do if you're into small-scale pinhole _ ...-:)) ...!!_ and can't get into the camera to dodge the center of the image. I personally have started to use a dodging tool in front of the pinhole, remembering that the pinhole has this infinite depth-of-field capacity and that it will pick the dodging tool in focus if you don't move it enough. With very wide angle-of-view pinhole imaging, your dodging tool needs to be very large and close to the pinhole to do the trick. You need to experiment a bit with the procedure, of course, but the results can be amazingly good! Andy's refers to graduated center-filters. They will do the trick with lens but not so much with pinhole. If the filter is placed in front of the pinhole, the later will pick every details of it because of the infinite DoF. You can try to place it behind the pinhole inside the camera, but this will create problems of light reflections all over the film... I guess what I actually like most with pinhole is the image distortions arising from the characteristics of the instrument. But, there are times when it just won't work and you have to search how to make some corrections. Fun... Enjoy pinholin', Greg! Best, Guy
