Sigma 150mm f2.8 Apo Macro OS in-depth review.

 
An example of what it means practically: How the distances vary to get  1:3 reproduction ratio with the nikon 200 micro AfD and with the Sigma 150 Macro OS:
 
 

 
If the little snake was real instead of being made of stone, I might have had some problem concerning safety (its or mine, it depends ).
 
 
 
 
Conclusion.
 
I think that the 150 Sigma OS is an  eccellent lens under all aspects, operationally better than the 200 micro nikkor AfD and, without splitting hairs too much, with the same overall image quality.  The problem of the huge reduction of the actual focal length still remains however, even at RR of 1:2  actual focal length is rather scarce for a lens labelled as a 150mm.
It does not prevent however that lots of macrophotographer make spectacular images with this lens (as with the 100-105 macros, to be honest). It is a matter of habits and ease of use. One has to choose  if it may be more beneficial for him the superior ergonomy and ease of use or the greater working distance.
For what it is worth the new Sigma 180 macro f2.8 OS behaves like its smaller companion or even better, and has a greater working distance, thus the problem is solved (apart for the price, size  and weight ).
 
My sincere thanks to Mauro (Rudolf) Maratta for allowing me to try this lens, and to my friend Gianni for the loan of the Sigma converters. 
 
 
Silvio Renesto