From: into@oblivion.nothing.com   
      
   Maybe I should have looked at the wikipedia article on   
   macro photography before I posted.   
      
   Seems I was on the right track. Because focusing close   
   causes a very obtuse light cone (numerical aperture) on   
   the objective, the DOF is accordingly much shorter.   
      
   And from that article I learned a few new ways of doing   
   macro photography that I hadn't known before, notably   
   the use of an infinity corrected microscope objective   
   attached to a telephoto lens, and attaching a reversed   
   short lens to the front of a longer focal length lens.   
      
   I already knew about lense reversing and extension tubes.   
      
   Brian   
   --   
   http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism   
   Sed quis custodiet ipsos Custodes?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)