The equivalence using a diagonal based "crop factor", from FourThirds
to Pentax "APS-C" is closer to 1.3x. So if you want to go this way
(sorry WR) I'd list:
FourThirds 50/2 -> 66mm focal length FoV, f/2.5 DoF.
(More accurate FoV transforms have to account for the format
difference: 1.23x V, 1.39x H. That is, a 50mm lens on a FourThirds
camera will produce images that look as if you fitted a 62mm lens on
the K10D, enlarged the vertical dimension to fit an 11x14 inch print,
then cropped the horizontal dimension to fit the print's width.)
I've come to see this FoV-DoF transformation very clearly in the past
year and some ... ;-)
Godfrey
On Mar 25, 2009, at 11:06 AM, Thibouille wrote:
Indeed that's what I find interesting with that kind of lens: macro
1:1 *and* speed.
As far as DOF is concerned I suppose we could sum it up (more or
less) as:
FourThird 50/2 -> APS-C 75/2.8
APS-C 75/2.8 -> 24x36 100/4
645D ??
Well thts just theory of course, not a classification of any kind.
Olympus has had the ZD 50mm f/2 Macro for years now. A superb lens,
ultra
sharp, wonderful bokeh, and the speed makes it useful for far more
than just
macro work. In actual macro photography, you normally stop it way
down
anyway.
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