How far can you close the Iris before the picture suffers?
 

I am not looking for a 'film look' or anything - I would actually like as big a dof as I can get but I don't want the picture to become too soft.

How how closed can the iris go with the EX1 and still give a decent picture?

so far f5.6 seems fine.

Anyone tested this? Whats 6.7 or 8 like?

thanks.

I haven't noticed any issues below F8. I know at 11 or 16 I have seen it become junk, which is not uncommon for most lenses. I think most lenses are optimized to be sharpest in the F4-F8 range.

Depends on ligh a bit I suppose but I have shot at f11 with no noticable abberation. I find f9.5 as good as f4 in most situations.