Hi--

>You may well be correct that absolute optimum is not achieved 2 stops
>down, but I have never seen a lens where the first two stops were not the
>most significant in image improvement, by far, with subsequent stops
>improving the image only marginally, at best.
johnchap@erols.com

>> >........................... and the fact that optimum lens
>> >performance is about 2 stops down, one does not shoot wide open.

I was reacting to the above, with which I don't agree.
You have a good point above, but there are many exceptions
(some f1.4 lenses that gradually improve from f1.4 to f8;
teles and macro lenses that are close to optimum wide-open;
zooms and super-wides that take many stops to become useable
in the corners). I think "f8 for optimum sharpness in the
center with good lenses for 35mm" is a more universally
true ROT...