==================
I was wondering if lens design ie. "internal" focus / Tamron or Tokina 300mm
vs "helicoid" / standard Zuiko 300mm could make a difference in the depth of
field if all else is equal.
To put my question another way. Will the depth of field be exactly the same
at 20 feet and at f5.6 with both types of lenses? Could the design of the
lens increase or decrease this depth?
==================
No, depth of field is the same.
Holding all else equal isn't possible. An internal focusing lens gets
shorter in focal length as it focuses more closely, which raises the
question of what is being held equal. If you hold subject distance
equal, then the internal focus lens does not take the same image focused
more closely. Since it is reasonable to assume we want to compare
DOF in the same images, each taken with each type of lens design,
we in fact waht to hold subject magnification fixed, and f-stop fixed.
If subject magnification and f-stop are held fixed, then depth of field
stays fixed, regardless of lens design.
Joseph
< 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 >
|