Originally posted by goubejp Right, at 10 meters a 600 at f4 has only 4 cms of depths of field; most of the time I stop my 600 to f8 to get 8 cms of depths of field to get managable depth of field
Perhaps you could confirm an observation that I think I have made with respect to long lenses and DOF. Specifically, I have spent some
time comparing the results of a couple Pentax exotics that I happen to own--- an FA*600 f/4 and an A*400 f/2.8 and a pentax dedicated
TC's.-- the 2x-L and the 1.4x-L sometimes stacked with another converter...
Answers I've been fishing for include whether Optical cropping (adding a TC) produced better results than Digital Cropping (cropping in Photoshop). One of the casual observations that I have made however. is that adding a TC to a lens doesn't seem to alter
the DOF characteristics of the lens, Thus if you were fairly close (lens to subject) where DOF could become an issue you could
use the A*400 with a mild TC (the 1.4x-L) --- and get the effective focal length of almost 600---- actually 560, but the DOF associated
with a 400mm lens instead of the longer focal length glass.
Guess I'm looking for some validation of what I think I've observed... but anyhow my present thinking is that the 400mm with a TC
is a pretty good gambit where DOF (or lack thereof) is going to be the spoiler of a photo. Or am I keeping my A*400 f/2.8 around
even though it has no chance of out performing the FA*600 f/4 no matter what the conditions....