I think it means that you are testing too much and not taking enough pics. I also think that your problems may be a symptom of having to be "first on the block." My DA* 50-135 focuses perfectly with my K20D at both 50mm and 135mm. I did adjust it. I think the number was -1 or thereabouts. Paul On Mar 22, 2008, at 8:32 PM, Joseph Tainter wrote: > My defective DA* 16-50 is ready to go to Pentax to correct the fact > that > it won't autofocus to infinity at 16 mm on the K20D. The K20D has > to go > with it. > > Before sending them off I thought I would check the focus > asjustment of > the DA* 50-135. I tested it at 135 mm, figuring that the most rigorous > test would be at that focal length because that's where the depth of > field is smallest. It turns out that an adjustment of -4 gives the > sharpest distance focus at that focal length. But then I noticed that > when I zoom the lens to 50 mm it now autofocuses beyond infinity, and > the images are not sharp. > > Arghhh! Okay, I guess the DA* 50-135 has to go to Pentax too to be > calibrated to the K20D. But this is disturbing and frustrating. I have > been concerned that it may be difficult or impossible to adjust the AF > of zoom lenses through the K20D--adjusting for correct focus at one > focal length could mean incorrect focus elsewhere. What I have seen so > far (with both DA* lenses) confirms that suspicion. > But there are larger implications: > > 1. Does this mean that I have to give up using autofocus zoom > lenses if > their focus cannot be uniformly adjusted? > > 2. Does this mean that every time I buy a new camera I have to send > the > body and all of my zoom lenses to Pentax to be calibrated to each > other? > > 3. Does this mean that every time I buy a new zoom lens I have to send > it and all bodies currently in use to Pentax? > > Or did I just get three bad DA* lenses (this is my second DA* 50-135) > and two bad K20D bodies? > > That's about $3000 worth of gear that I can't use. > > (Yes, I know, some of you will want to reply that your zoom lenses > work > fine. Please don't.) > > Frustrated, frustrated, frustrated. > > Joe > > -- > 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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