Dave and Cotty I seem to be learning a lot these days. My problem was/is, that when buying a new lens (in this case a 80-200mm F.2.8) I want to test it, Test results are depending on aaccurate focus. And I seem to hva a lot of trouble getting af F.2.8 shot sharp enouhg to evaluate properly. Is the lens bad, or is there a focsing problem, not caused by the lens? See some of my testes at: www.jensbladt.dk/Test
Later I have noticed, that if there's a contrasty part of the subject - a little above and behind the point where I want to focus, the canmera focuses on the contrasty part instead, disregarding the centre of the focusing screen in the *ist D. Havning done this shot (arm rest of my couch), I no longer doubt, that the FA 80-200mm is a sharp lens, even at F.2.8 (the image is a crop showing appr. 1/4 of the frame. This shot was done by focusing manually: http://www.flickr.com/photos/bladt/70368090/ Sorry for all this fuzz, but I don't spend up to 1000 USD on a lens very often, so when I do, I want to make shure, that it's worth it :-) Regards Jens http://www.jensbladt.dk -----Oprindelig meddelelse----- Fra: Dave Brooks [mailto:[EMAIL PROTECTED] Sendt: 5. december 2005 01:10 Til: PDML Emne: Back Focus Date: Sun, 4 Dec 2005 23:31:00 +0000 From: Cotty <[EMAIL PROTECTED]> To: "pentax list" <[email protected]> Subject: Re: A better 70-200mm F. 2.8 Message-Id: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On 4/12/05, Jens Bladt, discombobulated, unleashed: >All of them seem to suffer from Back Focus. Sorry to be a pain Jens, but the only back focus I have ever heard of in optical hardware terms is to do with manually adjusting the rear element (s) of a lens to achieve correct focus depending on what camera (video) a particular lens is mounted on. <http://www.rondexter.com/professional/equipment/adjusting_back_focus.htm> and <http://www.pentax.co.uk/cctv/technical_1.html> In a still camera application where back focus is usually not adjustable, do you mean that the lens is focussing on the wrong plane? Cheers, Cotty ____________________________________________________________________________ ________________ Cotty. The back focus problem a LOT of D1's suffered(as mine does) seems to be linked to a ~slightly~ out of aligned centre sensor,acording to Nikon.Although they have never officially admitted to this,will fix cameras that are sent in for the problem. Mine does this in poor light and if the contrast between subject and background is close.However its noticably in the viewfinder so for the most part i can recompose and get the shot. About the only thing the D2H does right is focus<g> and the istD has never experienced this , so far. David J Brooks Equine Photography in York Region www.caughtinmotion.com Pentax istD, Friggin Nikon D2H
