This theoretical crap is boooooooooooooooooooooring. Quite wasting your time mass debating the theory & go put it into practice by taking some interesting photos.
DS 2009/4/7 JC OConnell <[email protected]> > > NO I DISAGREE. Image DOF is the RELATIVE sharpness > of objects in front of, and behind, the actual plane > of focus. TO INCREASE OR DECREASE this relative > sharpness you have to change the incamera > magnification or f-stop. PRINT SIZE has nothing > to do with changing the DOF of an image. While > you can argue all day long that making a print > smaller and smaller increases the "perceived" > DOF, I dont, because all it does is make it > harder to see the **same DOF**, its doesnt actually > change the image DOF at all. > > Furthermore, I disagree with using the term > "critial" to define DOF. Its not critical, its > what it is, and thats simply the difference in > sharpness of foreground and background objects > relative to objects in the plane of focus. It > doesnt have to be some "critical" barely perceivable > difference, sometimes its huge and obvious. but > in any case, if you want to increase or decrease > that DOF, you need to know what CHANGES it, and > what DOES NOT. > > > JC O'Connell > [email protected] > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of > Paul Stenquist > Sent: Tuesday, April 07, 2009 8:35 AM > To: Pentax-Discuss Mail List > Subject: Re: Trading resolution for depth of field > > > This is a simple issue. Bob is speaking of perceived depth of filed on > a viewed print. JCO is speaking of critical depth of field in respect > to the ability of a given lens to resolve detail. Both are correct, > but each is discussing an entirely different matter. > > Let it go. > > > On Apr 7, 2009, at 4:02 AM, Bob W wrote: > > > Instead of making an unsupported assertion why don't you provide a > > formula > > for calculating depth of field? Then we will all be able to test your > > assertion. > > > > I have provided a formula which shows quite clearly that you are > > wrong. The > > calculation uses coc as a factor. The formula for coc depends on > > viewing > > distance and print size, therefore by changing either of these the coc > > changes. If the coc changes, the depth of field changes. You can't > > argue > > with the numbers. > > > > Give us a formula which shows you are right, then people might start > > to take > > you seriously. > > > > Jose > > > >> > >> NO WAY JOSE. you can never change the dof > >> after the shot, DOF is an "in camera" thingy... > >> you have to change the in camera image magnification or f-stop to > >> change the image DOF. > >> > >> JC O'Connell > >> [email protected] > >> > > > >> > >> > >> Coc is always a factor. > >> > >> You can change the viewing distance or the print size, and the depth > >> of field changes. > >> > >> Bob > >> > >>> > >>> The question was regarding relative DOF, COC is not > >>> a factor. The only way to increase DOF from whatever > >>> your reference is, is to decrease IN CAMERA magnification or > >>> increase f-stop number. All that other stuff is moot. You cant > >>> change the relative DOF of an image after you shoot it. > >>> > >>> JC O'Connell > >>> [email protected] > >>> > >>> > >>> > >>> -----Original Message----- > >>> From: [email protected] [mailto:[email protected]] On Behalf > > >>> Of Larry Colen > >>> Sent: Monday, April 06, 2009 5:47 PM > >>> To: Pentax-Discuss Mail List > >>> Subject: Re: Trading resolution for depth of field > >>> > >>> > >>> On Mon, Apr 06, 2009 at 10:32:37PM +0100, Bob W wrote: > >>>>> So, if I'm willing to trade resolution for depth of field, am I > >>>>> better off using a wider angle lens and cropping (my > >>> intuition says > >>>>> yes), or do I get the same benefit by just combining > >>> pixels (which > >>>>> would also reduce noise) for a larger circle of confusion? > >>>>> > >>>> > >>>> To calculate the nearest (dn) and furthest (df) points in > >> focus use > >>>> the following formulae: > >>>> > >>>> dn = U * F^2 / [F^2 + (U * c * f)] > >>>> df = U * F^2 / [F^2 - (U * c * f)] > >>> > >>> Ah. Thanks. Focal length is second order factor, circle of confusion > > >>> is first order, so focal length has a greater effect on DOF, than > >>> CoC (pixel size). > >>> > >>>> > >>>> where > >>>> c = circle of confusion > >>>> U = subject distance > >>>> F = focal length > >>>> f = f-number > >>>> > >>>> To calculate the circle of confusion > >>>> > >>>> c = (v * D) / (1000 * S) > >>>> > >>>> where > >>>> v = film format / image size > >>>> D = viewing distance > >>>> S = print size > >>>> > >>>> Source: The Professional Guide to Photo Data, 3rd edition, > >>> by Richard > >>>> Platt. > >>>> > >>>> Very easy with a spreadsheet. > >>>> > >>>> Bob > > > > > > -- > > PDML Pentax-Discuss Mail List > > [email protected] > > 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 > [email protected] > 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 > [email protected] > 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 [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
