OK, now you're talking complications. DOF is black art. To be really
scientific, the f stop required for a given acceptable image you need to
know sensor/film size, focal length, and the size print you expect to
make, (or the size of the image on any display for that matter), then
take into account viewing distance. A lot of that is assumed in the
simple DOF scales you see on lenses. Wikipedia actually has a pretty
good discussion of DOF calculation including the math here
<http://en.wikipedia.org/wiki/Circle_of_confusion>
On 12/2/2010 7:36 PM, Walter Gilbert wrote:
Thanks, Ecke ... that will be helpful down the road, no doubt.
I guess what I'm looking for is a combination of both. Nothing overly
scientific -- like down to the atomic level, or anything.
Maybe if I can explain the way I've grasped the concept of the effect
of aperture size on depth of field: I see it as analogous to pouring
sand through a funnel. If you use a funnel with a larger spout, the
sand is going to pile up on the surface underneath it. Whereas, if
you use a funnel with a narrow spout, the sand will spread out on the
surface beneath it. That's how I view light passing through a larger
or smaller aperture as it relates to the focus -- which, as far as I
know, is completely false.
If I could find something that gives a technical explanation, perhaps
formulas, and then an analogy to help it all sink in, it would help me
a great deal. I mostly don't want to sound like an complete idiot
when I go about explaining what I'm doing. :-)
Thanks again,
Walt
On 12/2/2010 6:24 PM, eckinator wrote:
Roman posted this link a while ago and I find it quite useful for
doing the math. Is it that or are you interested in the underlying
logic?
http://roman.blakout.net/?dof
HTH Ecke
2010/12/3 Walter Gilbert<ldott...@gmail.com>:
Hi all,
Being not particularly mathematically inclined (to put it very
charitably),
I was wondering if any of you could point me toward a sort of online
idiot's
guide to understanding and calculating exposure values, depth of
field, and
other basics along those lines. I figure having at least a loose
grasp on
details of that nature might be helpful as I dip a toe into the
world of
analog.
I've posted an entry on my photo blog concerning some of the basics
that I'm
already familiar with, and plan to chart my progress as I go along.
Granted, what I've written is geared toward people who know even
less about
photography than I do (as hard to conceive as that may be), but it
can be
found here:
http://waltgilbert.posterous.com/putting-myself-through-the-old-school
It's a first baby step on a long journey, but I'd like to document
it as I
go along, and share it with anyone who might be interested. So,
essentially, I do understand the stuff they probably teach you in
the first
week of Introduction to Photography 101 -- but largely on an intuitive,
practical level. Are there any resources on the web where a
simpleton can
go to familiarize himself with those principles on a more technical
level?
Thanks in advance for any help you can provide.
-- Walt
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