Archived posting to the Leica Users Group, 2001/02/08
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> > > In response to Jim Brick, austin@darkroom.com wrote "I believe you
> > > are 'confusing' DOF on the film with DOF on the printed image at
> > > viewed distance. They are different. Even on the print,
> then again at
> > > viewed distance have different 'DOF' too."
> >
> > > This theory confuses the issue even more. "DOF on the
> printed image at
> > > viewed distance" - there is no such thing!
> >
> > Of course there is such a thing.
>
> Austin- I respectfully disagree with you. You are confusing
> sharpness/resolution/mtf values with depth of field.
Not confused at all, they all are inter-related, and can play a significant
role in the DOF on the media.
> > You can make a print that has less resolution than is on
> the film, and thefore, it make things that aren't in critical
> focus on the film, be in as sharp a focus as the print can produce.
>
> This concept is of course true, but it is not OPTICAL depth
> of field
Agreed, but it DOES play a role on the DOF on the film, which was the point
of discussion. It is also NOT apparent, it is real, and can be measured.
In fact, it is not even subjective, ie, subject to criteria like 'optical'
DOF is ('optical' to distinguish it from what I will call 'thresholding').
> The OOF areas are still OOF.
Technically, no. 'Some' of the OOF is now just as 'in focus' as what you
are considering 'in focus' on the film. Obviously, the OOF areas that fall
below this threshold are still OOF...
> Your theory is true but it does NOT relate to depth of field.
It has the exact same result. I believe it is still 'depth of field' as it
relates to the linear distance represented in the image being in
'focus'...so I would contend it is still DOF.
> > Oh yes the DOF does change if the diffusing filter is
> diffuse enough to reduce the resolution of the lense lower
> than that of the film.
>
> No it doesn't. Here's where we need the new word. If
> someone can come up with "bokeh" to describe the look of OOF
> images, then surely we ought to be able to find a common word
> to describe this phenomena of the effect of lower resolution
> on apparent depth of field.
Well, given what I said above, I believe it can be called DOF. If you want
to come up with a word for it that is more specific to the cause, as opposed
to the effect (as the effect IS the same), that is fine with me!
Respectfully 'refuted' ;-)