Paul >"Back focus" is a term used to describe autofocus that misses the mark and locks in behind the subject. I think that it's most often the result of operator error. Or at least a product of using autofocus in a situation where one should be focusing manually.
This is exactly my perception/conclusion as well. Regards Jens Bladt http://www.jensbladt.dk -----Oprindelig meddelelse----- Fra: graywolf [mailto:[EMAIL PROTECTED] Sendt: 4. december 2005 22:30 Til: [email protected] Emne: Re: A better 70-200mm F. 2.8 The photos are rather too small to tell anything from. However, it is most likely an auto-focus problem, not one with the lenses. Try manual focus. After you have the proper part of the image in what you think is correct focus, go look out the window for 5 minutes or so, then come back and tweek your focus as quickly and exactly as you can. Now you can take your photo. Do that with the other lenses. Get back to us with the results. I would look at every other posibility with focus problems before blaming the lens. And by the way, from a technician's point of view back focus problems means the lens is not focusing the image exactly the flange to film distance from the lens mount. I do not think that is how you were using the term. graywolf http://www.graywolfphoto.com "Idiot Proof" <==> "Expert Proof" ----------------------------------- Jens Bladt wrote: >I have been trying out three different lenses in the 70-200mm range. >Sigma EX 2.8/70-200mm APO >Tokina AT-X Pro 2.8/80-200mm >SMCP-FA 2.8/80-200mm ED(IF) > >All of them seem to suffer from Back Focus. The Sigma not much, though. >Had I been offered a used Sigma, I probably would have bought it. > >I published a small test showing the problem. >Due to Back Focus (i BELIEVE), my SMCP F-4-5.6/70-210mm is the sharper one >at F. 5.6. > >Please take a look and feel free to comment: >http://www.flickr.com/photos/bladt/sets/1509814/ > >Regards >Jens > > > > > >
