no no no no no print size does not change DOF, never does and never will. DOF is "locked into" the image at time of exposure dude.
JC O'Connell [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of DagT Sent: Tuesday, April 07, 2009 5:59 PM To: Pentax-Discuss Mail List Subject: Re: Trading resolution for depth of field Hmmmm, now lets see... Yes, if you look at the picture from the same distance, you will sense that the DOF is larger if the magnification is less. But, if the picture is the same then you reduce the size of the print and the viewer will go closer and adjust the sensed magnification. If that is the case the viewer will sense the same DOF. If you reduce the magnification while the print size is constant then you have changed the lens, the size of the image sensor/film or a little of both, in which case the viewer will keep the same distance (unless he wants to look at some detail) and sense a different DOF. The effective resolution limits the possible magnification, viewing distance, and the possible range of DOF. But this is theory not practice. In real life people usually don´t let the sensor/film decide the size of the print. They want a print this size and they like the effects your photograph has in that size. In that sense the larger resolution, once it is sufficient at a certain viewing distance, has the effect of giving a possibility of moving in closer letting the image fill you field of view and at the same time see more details. In that process you can say that the DOF changes as you move into the picture. The sensed magnification changes as well as the DOF. So in some ways you are both right. (and by the way JCO, I´ve been making my own prints since 1977 so don ´t use your experience, it´s not enough :-) DagT Den 7. april. 2009 kl. 21.53 skrev JC OConnell: > I already stated you can choose ANY reference you > want ( a particular COC for example) it doesnt matter, > if you want to increase or decrease DOF, regardless > of your reference, only image mag/f-stop can CHANGE it. > > I think what your trying to do is define DOF absolutely, > via a maximum COC for example. This is fine if you know > and understand that concept. But changing your COC size > only changes the way you MEASURE the DOF, it doesnt > change the actual DOF. IF if WANT more or less DOF > it does not matter how you define/reference it, only MAG/FSTOP changes > will increase/decrease the DOF ***COMPARED TO YOUR REFERENCE, WHATEVER > YOU CHOOSE*** All the other varibles cancel out and your left with > only MAG and F-STOP to increase/decrease DOF. > > JC O'Connell > [email protected] > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf > Of > Bob W > Sent: Tuesday, April 07, 2009 3:41 PM > To: 'Pentax-Discuss Mail List' > Subject: RE: Trading resolution for depth of field > > > >> Sir, >> >> MY "burden of proof" is no greater than yours. >> If you cant provide any reliable "proof" >> that my contention is not true, then >> your word is no better than mine. > > You haven't supplied us with anything that is falsifiable. All you've > given us is unsupported assertions. > >> I dont need >> any more "proof" to support my contention than >> you need to support yours. >> > > I've provided you with definitions of terms, a mathematical formula > and > a published reference. Others have pointed you to definitions and > formulae which state the same thing as me, and which also have > published > references, including references from companies such as Kodak and > Zeiss > and the leading optical scientists. > >> This is very simple. DOF is all about magnfication >> and f-stop. >> >> I did supply the formula, >> >> relative DOF = F-stop number/MAGNIFICATION. >> >> INCREASING F-STOP NUMBER OR DECREASING IMAGE MAGINIFICATION increases >> the image relative DOF. >> >> Conversely, >> >> DECREASING THE F-STOP NUMBER OR INCREASING THE >> MAGNIFICATION decreases the image relative DOF. >> >> If you dont believe me, do some experiments. >> I have, its called about 35 years of practical >> experience to back up what I have read in theory. >> This isn't my theory, this is the correct theory >> that I have read and found to be true over the years. > > I have as much experience of practical photography as you do. I can > cite > theory, and I can provide references. You cannot provide references, > and > the formulae you have provided do not include definitions of terms > (such > as DOF), so they're useless. > > Give us a respectable reference which supports your claim and these > so-called formulae. > > 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.
