Thank you for your reply and suggestions, Javier. I lean toward your suggestion about the non-linerarity of the diaphragn ring positions as the cause of the behavior I'm seeing. The 28mm Tamrons work perfectly with either adaptor so it seems, to me at least, that either one is compatible with the R4's. _________________________________________________________________ Don?t just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/ ------ Unsubscribe or change to/from Digest Mode at: http://www3.telus.net/~telyt/lrflex.htm Archives are at: www.freelists.org/archives/leicareflex/