I have tried a visual method shooting out of the window across the street into a hedge with lots of details, but the little jpeg pic works very well too. In the end, that was the method I use. Popped it on the laptop and had a fiddle for a bit until all the lenses looked nice and sharp.

Of course, I'm moving to using the Natural style setting more these days which turns the sharpness down a bit, so it kind of defeats the object but at least I know they're right.

A couple of them needed quite surprisingly severe settings like -14 in one case. Seemed like a lot to me. Others were between 3 and 7