Archived posting to the Leica Users Group, 2003/04/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]On Thursday, April 24, 2003, at 01:55 PM, Jim Laurel wrote: > In the examples we've been talking about standard 35mm camera lenses > on film > vs DLSRs with small sensors, isn't the circle of confusion the same > since > the lenses are all designed to cover 24x36mm? The DSLR just crops the > frame. The circle of confusion depends on the ratio between the intended print size and the original image size, ie the degree of magnification you expect to use, as well as the desired resolution at the print. So cropping the frame changes the CoC, everthing else being equal. Every time DoF comes up people get confused. As always I recommend going through the derivation of the DoF formulae yourself until you really understand it. It's not that hard, basic Euclid really. The best tool for working with DoF that I have found is the following Excel spreadsheet which allows you to specify every possible variable and see how they interact. I have posted it on my own site because the original source seems to have disappeared. ftp://ftp.pinkheadedbug.com/pub/mdofcal2.xls.zip I also made this very very simple one for my own purposes, which you may find helpful. ftp://ftp.pinkheadedbug.com/pub/JBdof.xls.zip - -- John Brownlow http://www.pinkheadedbug.com http://www.unintended-consequences.com - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html