WRONG- format is the size of the image captured from the lens, changing the format or the size of the print does NOT change the depth of field created by the lens image. PERIOD.
JC O'Connell [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of William Robb Sent: Thursday, November 13, 2008 9:49 PM To: Pentax-Discuss Mail List Subject: Re: FA 1.4/50mm tested by DPReview ----- Original Message ----- From: "Matthew Hunt" Subject: Re: FA 1.4/50mm tested by DPReview > On Thu, Nov 13, 2008 at 9:26 PM, William Robb <[EMAIL PROTECTED]> > wrote: > >> Actually, it depends purely on the magnification ratio and alowable >> COC. Focal length doesn't matter, nor does subject distance. > > Your statement is only an approximation, useful for close subject > distances. See: > > http://en.wikipedia.org/wiki/Depth_of_field#Close-up > > "Stated otherwise, for the same subject magnification, all focal > lengths give approximately the same DOF. This statement is true only > when the subject distance is small in comparison with the hyperfocal > distance, however." > >> Don't try to correct John on this, he's forgotten more than most >> people >> know >> on the subject. > > I'm not "most people", and he's wrong. John disputes that the > allowable CoC, which you mention above, varies with format. I have > provided numerous sources that state otherwise, and offer clear > explanations. > Of course it varies with format. As an examle, you don't need to magnify an image from a 4x5 negative as much as you do an image from an APS-C sensor, so the CoC of the sheet film can be larger. However, trying to correct John is a fools game, no matter what your opinion of the facts are. William Robb -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
