I wouldn't call them zombies... Paul Stenquist wrote: > I suspect that back and front focus problems are almost always the > fault of the camera. I too have noticed the hysteria on the Pentax > forum. It's the result of some real problems that have now caused > paranoia and a search for problems where none exist. Some DA* 16-50 > lenses had a manufacturing defect that caused an uneven focal plane. > In other words, the right side of the frame might be in focus, while > the left side was not. This was a lens problem, but it seems to have > been relatively rare and confined to early samples. However, a second > condition has complicated the situation. It seems that early K10D > cameras were not properly set up for USM, and the firmware update > didn't do the job. These cameras backfocused with the USM lenses. > But it's apparently a simple fix, and it's not a lens problem. > However, the mindless zombies on some forums have blown all of this > way out of proportion. As you say, they test every lens, usually > handheld and in questionable conditions, and curse and complain. It's > an ugly situation, although brought on in part by some problems > Pentax created. > Paul > On May 6, 2008, at 7:30 AM, Andreas Pfotenhauer wrote: > >> hi, >> >> i recently followed a discussion in my favorite forum (bulletin >> board?) >> where a guy who had bought a DA 35/2.8 Limited was very disappointed >> because he found the *lens* to have severe back focus on his K10D >> while >> on his K20D it seemed to work just fine. >> >> As far as i understand it (with my limited optical knowledge), a lens >> can (and does) produce various forms ob optical aberrations, but if >> the >> "virtual image" is not directly on the sensor but in front or behind, >> then it's simply not properly focused, isn't it?! So the AF of the >> camera would be to blame for not acting accurate or, as second >> possibility, sensor, AF sensor and/or focusing screen are not leveled. >> I was asking if someone with a deeper understanding of the optics >> could >> confirm or denial this, but no one was able (or wanted) to, thats why >> I'm asking here now :-) >> >> The reason why I'm so interested in this is: a increasing number of >> ppl >> in that forum now test their newly bought lenses with a printed test >> chart under more or less undefined light conditions, of course they >> find >> some back- or front focus (of you look hard enough you surely find >> something to worry about, I'm 100% convinced), and then they send >> their >> lenses back, open new threads in the forum where they loudly complain >> about lens qualities, unsettle some more who start testing their >> lenses >> ... you get the drift. >> >> I would be deeply grateful if someone could shed a light on this, so >> this can be settled once and for all. >> >> Free beer is offered if that one will ever visit Frankfurt, >> Germany ;-) >> >> cheers >> Andreas >> >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above >> and follow the directions. >> > > >
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