Archived posting to the Leica Users Group, 2003/04/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Johnny, I have two video cameras - a Sony PD-100, which uses 1/4" CCDs, and a PD-150, which uses larger 1/3" CCDs. Now, when I put both cameras side by side on tripods, set them to the same aperture, and frame a shot identically, the PD-150 picture exhibits markedly shallower depth of field than the PD-100. And when you do the same comparison with a camera that has 2/3" chips, again set to the same aperture, and with the subject framed exactly the same, the 2/3" camera 's picture exhibits even less DOF than the other two. Why is that? - --Jim - ----- Original Message ----- From: "Johnny Deadman" <lists@johnbrownlow.com> To: "Leica Users digest" <leica-users@mejac.palo-alto.ca.us> Sent: Friday, April 25, 2003 11:23 AM Subject: [Leica] DOF tech stuff was Digital Aesthetic > 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 - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html