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Wednesday, May 19, 2010

Focusing Issue with the DA 17-70/4 SDM

Recently I have seen four user reports by four different owners of the DA 17-70 about the inability of completing AF with the lens in the range of 50 to 70mm, in a Chinese forum. Direct links are as below:-

http://www.dchome.net/viewthread.php?tid=875053

http://www.dchome.net/viewthread.php?tid=875053&page=1#pid10272648

http://www.dchome.net/viewthread.php?tid=871324

http://www.dchome.net/viewthread.php?tid=871324&page=1#pid10221635

(Above: First Three Posts are in Traditional Chinese, the Fourth is in English)

So, what's going on? What happens for those lens units? What causes the problem? Design issue(s)? Quality issue(s)? Or Both??


Previous Related Articles:-

SDM Issue Strikes Again - This Time DA 17-70

The SDM Petition Online

SDM Reliability Issue
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Comments (8)

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special flied lice's avatar - Go to profile

special flied lice · 773 weeks ago

not only a pentax issue. If your sorry ass would have taken the time to read from other idiot-proof forums, you would have noticed that this is also an issue with nikkor, canon and sigma zoom lenses at different ranges. My Canon 50D always struggles with the 18-135mm lens when focusing past 70mm up to 105/135mm if light conditions are not favourable, yet i don't think this is a quality issue but rather a limitation with the vast majority of low-mid end AF zoom lenses. In the end with a little patience and some practice you learn how to overcome these issues by simply getting to know the gear you use.
2 replies · active 771 weeks ago
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RiceHigh's avatar - Go to profile

RiceHigh 110p · 773 weeks ago

Beware of your wordings when you are trying to make a reply. Be civilised and be respectful to other people, if you really want to express your views and put forward your comments!

In response to your "point" that you are trying to make, I have no problem with my FA 24-90 on any of my Pentax DSLRs for years at the longer focals and so does any of my 18-55 kit lenses (different models) on any of my Pentax DSLRs at 55mm. So, why does the 17-70 SDM alone should have the issue? I really doubt if you do have a Canon 18-135 actually. But in fact, I have experienced no issue neither for that lens used on a 550D.
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Walter's avatar

Walter · 771 weeks ago

You must mean by using manual focus...
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Luk's avatar

Luk · 772 weeks ago

I have the same problem, my 17-70 was i in polish Pentax service and they sent me a opinion that lens (SDM) is all right :(
1 reply · active less than 1 minute ago
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RiceHigh's avatar - Go to profile

RiceHigh 110p · 772 weeks ago

I suspect the SDM is just moving too fast for the AF sensor to detect the focus. At longer focals, the DoF decreases, so the focusing motor should move slower to cater for this.
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Walter's avatar

Walter · 771 weeks ago

Those reports must be in error!

I have read hundreds of times that RMabo's 17-70 has no SDM problems. It is flawless! All his Pentax equipment is flawless.
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don2hmr's avatar

don2hmr · 760 weeks ago

I am afraid 17-70 is already the SDM one with least problems, not to mention 16-45 and 50-135. And it appears that most of these problems are associated with the K20D body.
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RTogog's avatar

RTogog · 591 weeks ago

Mine just live again !. I did cleaning its contacts and switch to MF, then did some movement to its focus ring several times. After so live witch back to AF, the auto focus return to live again. I realize now, it is hard to not believe the SDM is reliable. I will make sure to have second lens as backup if outing with this lens.

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