Archived posting to the Leica Users Group, 2001/02/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Bravo Johnny D. You can see clearly and your information is right-on regarding DOF, COC standards, etc. Contrary to what Austin might believe, the reference standards applied by Leitz, Zeiss, Nikon, Canon, and other top lens manufacturers, in determining the depth of field of their lenses, are all very close. It is very hard to help others learn, when they don't evaluate what they hear or read in a scholarly open-minded way. If one covers one's ears, all they will hear are themselves. Regards, Rob McElroy Buffalo, NY Johnny Deadman wrote: > on 2/8/01 2:02 PM, Austin Franklin at austin@darkroom.com wrote: > > >> I do not understand why some people cannot accept that the generally > >> accepted definition of coc and depth of field is in fact tied to film > >> size. > > > > I understand that you have cited some unknown, unsubstantiated, reference > > (of which I am not saying you don't know the source, and can't substantiate > > it) that claims this, but that doesn't make it 'correct'. It just makes it > > some amorphous method that some manufacturer supposedly uses. > > > > As has been pointed out, how DOF is 'determined' should be re-thought, and > > possibly standardized, or at least certainly qualified. > > Austin, Austin, Austin. > > Did YOU bother to look up the definition of DOF before you wrote that? > > The Focal Encyclopaedia of Photography is totally clear about it, as is > Ansel Adams (and I might say every other photographic reference I am aware > of). Go through the derivation, which is not at all difficult, standard > Euclidian stuff, and you'll see that it is not remotely amorphous. In fact, > the accepted definition of DOF is remarkably well thought out, even if you > disagree with it. It assumes perfect lens, perfect film and perfect > printing, and is keyed to a standard degree of magnification, which differs > according to format. > > It is, moreover, TOTALLY standardized. > > In other words it represents a usable MAXIMUM apparent depth of field at a > given degree of magnification. This is very useful and simple. The only > issue I have with it is that the CoC values assume you'll only look at eg > 8x10s from 35mm. It's childs play to substitute whatever CoC values you like > according to the magnification you expect. > > Your version of DOF may have its uses, but it isn't DOF as generally > understood, which is why you need to call it something else, as I suggested > a while back. Then perhaps people can evaluate it rather than arguing with > you. > > Stop digging! > > -- > Johnny Deadman > > http://www.pinkheadedbug.com