You are probably right, Rob. >From the PDML postings I got the impression, that some lenses are prone to consistantly causing the camera to (auto)focus behind the centre subject. I seem to have got that wrong. Regards
Jens Bladt http://www.jensbladt.dk -----Oprindelig meddelelse----- Fra: Rob Studdert [mailto:[EMAIL PROTECTED] Sendt: 6. december 2005 00:50 Til: [email protected] Emne: Re: SV: A better 70-200mm F. 2.8 On 5 Dec 2005 at 23:31, Jens Bladt wrote: > 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. It seems that the term has recently changed meaning, as far as I'm aware it used to refer to setting the absolute focus on the image forming plane when the taking lens was set to infinity. Back focus changes slightly with aperture in some fast lens designs, my Noctilux displayed such behaviour. I think we are just discussing focus errors. Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
