Archived posting to the Leica Users Group, 2001/02/08

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Subject: RE: [Leica] how can the 75 Lux focus go bad? NOW - DOF
From: "Austin Franklin" <austin@darkroom.com>
Date: Thu, 8 Feb 2001 12:52:22 -0500

> >To say DOF is not real is absurd (not my first choice of
> words mind you).
> >DOF is real.  There may be no 'recognized standard' criteria
> for measuring
> >DOF, but it is measurable and is real.
>
> Right Austin, I said it!
>
> Go put your hand on DOF and tell me about it.
> Tell me how it feels.
> You can't !!

So if you can't put your hand on it, it isn't real, right?  I certainly can
see it (and so can most other people), but I guess to you that doesn't make
it real.  You definitely get the 'absurd statement(s) of the day' award,
Henry.  Go stand outside in your shorts when it's 20 below and tell me cold
doesn't exist because you can't put your hands on it.  I do believe your
hands will be on something that IS cold though...and if you wait long
enough, you'll certainly see the effects of the cold that isn't real...

> The term DOF is something that was generally agreed upon
> before either
> one of us was born. But it only describes a phenomenon. That
> being human
> perception of something being in focus when it is not.
>
> DOF is an acceptable variation from the plane of focus.

Sure is, and it can be caused by different sources.  That's the part you are
not understanding, or possibly accepting.

> It is not a property of a print.
>
> "Print" DOF is your new term and it is INACCURATE in that you are
> apparently using it to measure resolution of a printing
> system and the
> subsequent degradation of the image so that the appearance is
> altered.

Well, it's still DEPTH OF FIELD.  Jim understands it, Johnny understands it,
I understand it, and my guess is others do too.  If you want to qualify the
result with the cause, then go ahead, but the result IS the same, no matter
how much you want to argue about it.

Do you actually understand it, and just want to argue semantics (for what
ever reason)?

> Are you going to make up a whole new terminology of photography?

No, just giving an explanation for the difference people see on different
media, and why.

> I will give you that what you are calling "print DOF" can be
> an issue in
> the look of a print but its not about DOF.

Even though the result is the same, you believe that depth isn't depth, and
field isn't field.