Archived posting to the Leica Users Group, 2001/02/08
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Rob McElroy jotted down the following:
> Some of this confusion can be summed up by understanding the difference
> between OPTICAL depth of field (which is calculable and found on the DOF
> charts that are on the internet and in countless reference books) and APPARENT
> depth of field (which is a subjective interpretation of what "appears" to be
> in focus by a given observer).
OK, explain how OPTICAL depth-of-field could exist independent of
(a) the essentially arbitrarily chosen 0.03mm CoC size,
(b) an observer.
The definition of depth-of-field is "that which appears to be in focus
around the plane of focus". Notice that "a"-word (no, not "around", the
other one ;)
As an exercise to the reader, you assignment for this week is to figure out
where the CoC size of 0.03mm for 35mm film comes from. Consider the
hypothetical case where human actuity was 100 greater than it really is.
How would that affect the CoC size and what Rob calls "optical DOF" above?
M.
- --
Martin Howard | "Common sense is just the layer of
Visiting Scholar, CSEL, OSU | prejudices put down before the age of
email: howard.390@osu.edu | eighteen." -- Albert Einstein
www: http://mvhoward.i.am/ +---------------------------------------