Jim Davies wrote:
> DOF is no different on an EOS than any other camera. It's 1/3rd in front
> of subject, and 2/3rds in the back of subject.
Eegads, not this!
Grind through the equations a bit, and you'll quickly find that the
1/3 front, 2/3 back rule of thumb is uselessly inaccurate. For example,
at high magnifications, and large apertures the ratio approaches 50-50
(i.e. the front DOF is roughly the same as the rear DOF). At hyperfocus
(achieved at small magnifications and/or very small apertures) the ratio
is 0 - 100, because the front DOF extends forward to half of the focussing
distance while the rear DOF extends to infinity, and any finite number
divided by infinity is still 0 ;-).
> I'm not sure how many shots
> you're judging this result on you got, but if you get focus lock on say a
> person at 20 feet, you should see more in focus to the rear of the person
> than to the front.
This is a reasonable expectation provided that you include the whole person
in the frame (i.e. magnifications on the order of 1/50 or smaller) and that
you use a middling-to-small aperture (say, f/5.6 or smaller). If you're
shooting a head-and-shoulders crop or if you're wide-open at f/1.4, then
the DOF will be more uniformly distributed front-to-back.
-- Patrick
*
****
*******
***********************************************************
* For list instructions, including unsubscribe, see:
* http://www.a1.nl/phomepag/markerink/eos_list.htm
***********************************************************
