At which aperture is this lens the sharpest?

Is there a table with a listing of various lenses with the aperture at which their 'normally' known to be their sharpest?

I guess the rule of thumb setting is f/8 but from experience with various lenses like the 'kit lens' .. it starts getting really sharp when used at f/5.6 and up. etc.

Think it would be a good reference point for many members ...

It varies on the lens and maximum aperture. F5.6 or f8 is usually tops.
You can try photozone.de

Rule of thumb...

This is probably about as accurate as the shutter speed=1/focal length formula - which means not very accurate at all:

Lenses normally are sharpest about two stops down from their maximum aperture. However, there are some lenses such as the 400mm f/5.6L that are as sharp (and that is pretty darn sharp) wide open as when stopped down.

"f/8 and be there" is the photojournalist's creedo.

But I've found almost all of the Canon lenses to be quite sharp stopped down one stop.

There are a few exceptions, lenses that rock wide open: 85L, 135L 200/2L....

Looking at photozone, it seems to be about 1-2 stops. The old adage was about 2-3 stops, so for a f4 lens that would be f8-11 but maybe modern lens design is getting better.

There is no one single aperture that all lens are their sharpest at, simply because there a a wide range of max apertures lenses are sold with. In general, you will find that the sweet spot of most lens is about 2 stops down from wide open.

AeroSmith wrote in post #5699339
There are a few exceptions, lenses that rock wide open: 85L, 135L 200/2L....

Notice what letter each of those lens have in common...

So, there you have it, about 2 stops, but as others stated, each lens is different. For instance, I've had 3... 50L's two of which were super sharp by 1.8 and didn't get much sharper past that, the 3rd, which I currently own is as sharp as the others at 1.4. Same with the two copies of the 100-400's I've owned, while both were sharper than some others I've seen, the one I own currently is sharper wide open than the first copy I owned....So, again, each seem to have their own individual "sweet spot", this is a "your mileage may vary" deal. I'm pretty sure humans make these lenses, so you will have variances.

Agree with comments above. 85L is wicked sharp wide open, doesn't really improve stopped down.