Great! Thank you, Peter (did I get it right from P. J. ? :-) ) and Kostas! Those links are indeed very helpful!
Again, many thanks to all who responded. Igor PS. As you might have guessed, I am considering some "enablement" :-) So, if you are considering selling any of Pentax SMC f/fa/d-fa 100/2.8 macro and/or f/fa 138/2.8, please contact me off the list. Well, I am also considering Sigma 100-300/4 - so if you want to get rid of one, - let me know. PPS. I hope this type of solicitation is ok on this list.
