----- Original Message ----- From: "Shel Belinkoff" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, January 01, 2002 10:16 AM Subject: Re: Questions for Beseler 23CII Users
> Hi Tom, > > How did you arrive at this conclusion? What's the math behind it? > Might be worthwhile to know. Basic geometery. The size of the diffuser needs to be somewhat bigger than the diagonal of the negative. As an example, the 35mm format is nominally 24x36mm. To get the diagonal, add the squares of the length and width together, then take the square root of that sum: (24 x 24) + (36 x 36) = 1872. The square root of that is ~43.266 mm. This is the minimum size needed to cover a 35mm negative, providing the covereage extends right to the edge. In reality, coverage should extend several millimeters beyond the negative corners to prevent light source vignetting. Interestingly enough, that length is also considered the standard focal length for 35mm photography, but I digress. William Robb > > Tom Rittenhouse wrote: > > > > My calculator says a 9x9 negative requires a 12.8cm diameter coverage. I > > don't believe a their comdenser head 23C can cover that. A 6x9 image requirs > > 10.8, so to cover 9x9 the light source needs to be almost an inch bigger > > than to cover 6x9. - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
