C.H. Ling writes:
<< I also agree MTF is a very useful tools and the charts are much more
useful then the overall rating. bUT I have one question, does any one
know how Photodo check the MTF of center and edge? what important is
will they refocus on the edge before they take the reading? If a lens
has high field curvature then the edge MTF will be very poor (because
you focus only at the center) but the real picture on the field may not
be that bad. >>
It's my understanding these are instrumentation readings, thus
independent of focus and curvature of field concerns. But I still have
lots to learn on the subject.
Should we be focusing on the center of a subject? Now that I use 2-4
series screens and mostly lenses with fine corner performance, I can
check focus on off-center objects without repositioning my camera. Field
curvature concerns . . its just part of a visual depth of field check on
screen.
Gary Reese
Las Vegas, NV
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