Howard,
You may be right.
As your web example suggests, there is an "hour glass" of light
transmission, with a focal point known as "focal node" in some circles.
Unfortunately, I have seen depth of focus and depth of field used
intermittently for the same discussion.
I also thought what you were referring too, was known as focal plane. Hence
the old days when we used "focal plane" shutters.
Take care,
Gregory david Stempel
FIREFRAMEi m a g i n g
www.americanphotojournalist.com
www.soundexposure.org
