andy_coach Posted February 19, 2012 Share Posted February 19, 2012 <p>After several hours of trying to fine tune two Pentax AF lenses with front and back focus, on my K-5, I am giving up. Could someone please suggest where I can send the camera and lenses to be calibrated? Thanks a bunch in advance.</p> Link to comment Share on other sites More sharing options...
ricardovaste Posted February 19, 2012 Share Posted February 19, 2012 <p>Are they zooms? Sometimes a "bad" zoom will focus differently (incorrectly) at different focal lengths. Not a great place to be in.</p> Link to comment Share on other sites More sharing options...
andy_coach Posted February 19, 2012 Author Share Posted February 19, 2012 <p>Yup, they are zooms, unfortunately. One is a Sigma 18-50 the other is the Pentax 12-24. They both respond to the AF fine-tuning but just not enough and I don't seem to be able to get the same results consistently after adjusting ff or bf. At 50mm, the Sigma is "almost" there but focus accuracy is horrid at 18mm. The Pentax is off the tuning scale, it seems. This is definitely more than I know how to fix.</p> Link to comment Share on other sites More sharing options...
ukhov Posted February 19, 2012 Share Posted February 19, 2012 <p>-it may tune itself on amount of use ,if lens new?!</p> Link to comment Share on other sites More sharing options...
r.t. dowling Posted February 19, 2012 Share Posted February 19, 2012 <p>Are either of the lenses still under warranty?</p> Link to comment Share on other sites More sharing options...
michael_elenko Posted February 19, 2012 Share Posted February 19, 2012 New or used? What is you focus testing methodology? ME Link to comment Share on other sites More sharing options...
andy_coach Posted February 19, 2012 Author Share Posted February 19, 2012 <p>Good idea on warranty.. I am researching it, I may still have some left on the Sigma, not sure about the 12-24, got it used from Amazon. <br> I used <strong> </strong>Yvon Bourque's AF chart to adjust the focus.<br> Maybe I can bribe a forum member to give it shot? :)</p> Link to comment Share on other sites More sharing options...
michellemandat Posted February 20, 2012 Share Posted February 20, 2012 <p>IMHO some zooms are prone to give BF/FF except 18/55. Calibration w'll do nothing.</p> Link to comment Share on other sites More sharing options...
michellemandat Posted February 20, 2012 Share Posted February 20, 2012 <p>IMHO some zooms are prone to give BF/FF except 18/55. Calibration w'll do nothing.</p> Link to comment Share on other sites More sharing options...
mattluther Posted February 20, 2012 Share Posted February 20, 2012 <p>How about your other lenses ? And do you use any general setting for the body?</p> Link to comment Share on other sites More sharing options...
andy_coach Posted February 20, 2012 Author Share Posted February 20, 2012 <blockquote> <p>How about your other lenses ? And do you use any general setting for the body?</p> </blockquote> <p>All my AF primes are dead on, e.g. the 35/2.4, 50/1.4, or the 400/4.6. The Sigma 70-200 focuses accurately as well.<br> What do you mean by "general setting for the body"? Are there other settings that could throw the AF off?</p> Link to comment Share on other sites More sharing options...
andy_coach Posted February 20, 2012 Author Share Posted February 20, 2012 <p>Good news, I've rediscovered a local Pentax and Sigma repair shop, www.criscam.com, I used them once years ago and had assumed they'd gone out of business. Turns out C.R.I.S. is still around and I will be taking my K-5 and the two lenses to them this week. They were a bit incredulous to hear that K-5's AF fine-tuning tool did not do the trick for either lens but agreed to look at them nonetheless. I will report back. Thanks a bunch for your replies, they're very appreciated.</p> Link to comment Share on other sites More sharing options...
mattluther Posted February 21, 2012 Share Posted February 21, 2012 <p>I meant the Apply All-setting, which really should be named Apply <em>to</em> all. I just wanted to get a hint about wether this was a generally troubled body or not.<br> I have a 12-24 and use the +1 setting on it, but they are quite individual of course. I'm a little sceptical about using the focusing charts on wide lenses, especially a zoom. You are likely to be off at some focal length. And then the testing is done at a distance you hardly ever use in real life. To get the chart large enough in view at 12 mm the camera back has to be at 40 cm. The lens hood is then 20 cm from the subject.<br> Not being able to focus at infinity is worse. If the shutter is set to focus priority, it will not release at all. </p> Link to comment Share on other sites More sharing options...
miserere_mei Posted February 22, 2012 Share Posted February 22, 2012 <p>Andy, CRIS is now the official repair center for Pentax USA. Pentax HQ in Colorado no longer provides repair services if I'm correct.</p> <p>And for what it's worth, Pentax would only calibrate your lenses and body if they were Pentax brand, so you're lucky if CRIS calibrates your Sigma lens.</p> <p>I have a Tamron zoom that is a bit wonky on my K10D (which doesn't have AF adjust for individual lenses). It focuses perfectly at the long end but often backfocuses at the wide end. The solution? I focus at the long end then zoom out to take the shot.</p> Link to comment Share on other sites More sharing options...
andy_coach Posted April 21, 2012 Author Share Posted April 21, 2012 <p>I am happy to report that the repair shop did a great job, the lens now accurately focuses at both ends, fully open. The adjustment was done "as a courtesy" since (as the Sigma rep explained) the lens was still under extended warranty AND this was not a repair. All is good :)</p> Link to comment Share on other sites More sharing options...
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