Hey Tom >From the little experimenting I've done, fall off is significantly reduced by a circularly curved film plane. Especially if the radius of the curve is about the focal length. It's just hard to bend film holders & Polaroid film packs.. 8o) andy
-----Original Message----- From: pinhole-discussion-admin@p at ??????? [mailto:pinhole-discussion-admin@p at ???????]On Behalf Of Tom Miller Sent: Sunday, March 16, 2003 12:09 AM To: pinhole-discussion@p at ??????? Subject: RE: [pinhole-discussion] 6x22 pinhole camera coverage?! Guillermo wrote: The aperture is irrelevant, the only thing that matters is the ratio width of format to focal length (corner-corner distance to focal length if one wants to be exact). The ratio of that camera is 3.6 which in theory will have a 4.25 stops fall off at the sides with respect to the center, this kind of fall off is horrendous for glass photography, but for pinhole images, in practice, it doesn't look as big as one may think, IMO. As an example, this image http://members.rogers.com/gpenate/greek.jpg is a portion of a larger image made with a camera with ratio 3 width/focal length, that should give a fall off of 3.4 stops at the top and bottom of the image with respect to the center, and if you ask me, it doesn't look that big of a fall off. This put two questions in head. First, would a concave film plane reduce the fall off ratio? Optimally, the film plane could be curved in a way that makes the entire film plane equally distant from the pinhole. I looked at the 6x22 camera's photo on the silver-whatever web site and it looked like it could possibly have a curved film plane, although I couldn't tell if would be hemisperical like the Mottweiler Pinoramic. Second, what is the formula that you used to calculate the fall off? I'm curious because I've been doing a fair bit of extreme wide-angle stuff lately and it doesn't seem like the light falls off as much as one would think. It is a flat film plane camera with a 1:3.7 ratio. I've read a rule of thumb that at 30 degrees the fall of is one stop and that at 45 degrees it is two stops. It seems like there is a possibly handy formula in there. Thanks, Tom _______________________________________________ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??????? unsubscribe or change your account at http://www.???????/discussion/
