Sharpest Aperature for these lenses

[WSpruance]

I have tried to interpret the lens graphs available on the Internet without success. I know every lens has a best aperture (sharpest) for the individual lens. Can someone please provide this aperture setting for the three lenses that I have listed below.

Thanks in advance........

[slejhamer]

The general rule that I recall is that critical aperture for a lens is 2 stops down from wide open. So, if you have a zoom that varies aperture with focal length, the critical aperture will also change.

Example: on the 28-135mm f3.5-5.6 lens, at 28mm critical aperture would be f7, and at 135mm it would be f11.

Correct me if I'm wrong.

[lightandlife]

To me, aperture is of a lesser concern. When using a zoom, I would avoid either end, unless it is a matter of getting something or nothing.

From the series {28, 56, 112, ...}, the zoom is roughly a 5X zoom. It wouldn't be sharp at either end (X and 5X). One would get acceptably sharp images between 2X (or 1.5X) and 2.5X, and sharpest somewhere in between and almost as sharp as a prime. This is just a conjecture.

[Vegas Poboy]

Most of the lens that I've read reviews on is f/8. Most of the time thats the setting I use on AV mode.