I just got shown this very interesting artical by Ken Rockwell about the use of apeture and its effect on, where a smaller apeture produces a sharper image and that an apeture of f8 or wider should be used for maximum unless is absolutely necessary.
I don't know if other people know about this already (I may just be lacking in knowledge ) but thought I'd share and see what peoples thoughts were.
Here is the artical:
And here is another artical from someone else:
http://www.cambridgeincolour.com/tutori ... graphy.htm