At 17:24 1/17/00 , Brian Windrim wrote:
>Unfortunately, depth-of-field is determined geometrically
>by subject distance and the effective diameter of the lens'
>entrance pupil. No "implementation tricks" can alter this.
>
>Therefore, for a given focal length the depth-of-field will
>always be the same between different lenses at the same
>aperture (provided that the apertures are accurate).
In conjunction with these parameters, absolute values for DOF are defined
by the largest acceptable "circle of confusion" on the resulting image.
This is how out of focus an image (or parts of it) can be before it is
noticeable to the "average observer" of a print at a "normal" viewing distance.
The general accepted standard for 35mm is 0.03mm, however some others (Carl
Zeiss and Sinar) have used 0.025mm, and there has been debate about some
manufacturers using larger standards for marking DOF on their lenses.
The question this has brought to mind: What circle of confusion diameter
does (did) Olympus use for marking DOF with the Zuiko lenses?
Basics about circle of confusion related to DOF
can be found here (see Q8 and Q11):
http://www.photo.net/photo/optics/lensFAQ.html
A more detailed tutorial can be read here:
http://www.photo.net/photo/optics/lensTutorial.html
-- John
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|