One could buy a stainless steel ruler and a small mirror at Office Depot and devise a home brew setup. I would like to see some posts on how this could be done.
There are already lighter
focus test charts on the web, in this kind
(I got one really neat at home, from a single sheet of paper, with little tabs for easy assembly, and moreover it does not only works with pentax cameras but just can't retrieve its URL). (Edit : I found how-to instructions with a nikon version here
and a no-brand one here
For the DoF repartition problem, it's easy to compute with DoFmaster
- and anyway as long as the 0 target is sharp, result is OK.
The DoF extension can hide any moderate stop-down focus shift - but anyway it is to be considered as it affects also real-world focusing.
Field curvature can be set aside by using only the center part of the image, at the expense of resolution...
And the main variable is maybe subject distance, which I've heard can significantly affect focus accuracy (ie some lenses/cameras combo performing very well with a camera/test chart distance of 2m and not so well with the camera/snow leopard distance of 35m) : best tested with the real-world value... that may involve big test targets (hence the need to DIY).
Edit : Re-thinking to it, there is another variable to estimate : for a given camera, the reproductibility of results (ie AF accuracy)... Not to mention the need for this accuracy of course.