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02-19-2015, 09:42 AM   #1
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18-135 Focus losses when zoom out

I just received my new K3 and also the 18-135

I am in love with the camera but not crazy for the lens. Anyway, too soon to express opinions.

One thing I noticed is the out of focus when zooming out from 135.
Is this normal? If yes, why?

Thank you

P.S. zooming all in to focus, it's a technique to find the most accurate focus on a subject. This may be old school but it's my habit since 84 and so I noticed this problem on this lens right away. I never seen this on other DSLR before

02-19-2015, 09:46 AM   #2
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The ability to maintain focus while zooming is not common to all zoom lenses. I assume you are using manual focus, because using auto-focus the lens will refocus while zooming and you'll never even know. Try giving the AF a chance.

It's an ability that was much more critical before AF. You could zoom in and magnify then back out and maintain your focus point knowing the actual spot you wanted to be in focus was in the sharpest possible focus. These days, use your selective focus points to actually focus the AF on the point you want to be in focus. Functionally it's the same, only faster, except for maybe macro work and stacking, and why you'd be using a zoom lens for macro work would be an unknown.
02-19-2015, 10:36 AM - 1 Like   #3
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https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/201887-list...om-lenses.html

The DA 18-135 is not a Parafocal lens. It does not maintain focus across the zoom range you have to refocus at different zoom ranges.
02-19-2015, 11:56 AM   #4
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QuoteOriginally posted by normhead Quote
The ability to maintain focus while zooming is not common to all zoom lenses. I assume you are using manual focus, because using auto-focus the lens will refocus while zooming and you'll never even know. Try giving the AF a chance.

It's an ability that was much more critical before AF. You could zoom in and magnify then back out and maintain your focus point knowing the actual spot you wanted to be in focus was in the sharpest possible focus. These days, use your selective focus points to actually focus the AF on the point you want to be in focus. Functionally it's the same, only faster, except for maybe macro work and stacking, and why you'd be using a zoom lens for macro work would be an unknown.
Thank you mate!

Yes I know how to use the autofocus and of course I give it the chance, even though only in fast situations. I like manual focus. You take that away from me, I feel like being makin love to a woman without kissing her. You know what I mean.

---------- Post added 02-19-15 at 01:57 PM ----------

QuoteOriginally posted by UncleVanya Quote
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/201887-list...om-lenses.html

The DA 18-135 is not a Parafocal lens. It does not maintain focus across the zoom range you have to refocus at different zoom ranges.
Ok that's it. I didn't know this. I am behind tech wise I guess.

Thanks a lot!

02-19-2015, 12:09 PM   #5
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QuoteOriginally posted by igabc Quote
Ok that's it. I didn't know this. I am behind tech wise I guess.

Thanks a lot!
No worries. Glad I could help - at least within that thread you can find a list of those that seem to be Parafocal and know when you can still use the technique you like best. The varifocal lenses may have become more popular with the increase in autofocus and the reliance on computer modeling for lens designs.
02-19-2015, 12:25 PM   #6
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Yeah... I am lucky I have took very good care of my set of 6 prime vintage SMC lenses used on my old MX.

Autofocus : photographer = microwave ovens : cook

:-P
02-19-2015, 01:50 PM   #7
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I am going to return this lens. I would buy it for just 100 USD. Not more than that and definitely not for 280.

I don't even consider it a photography lens. It's good as a molecular, to get closer to subjects, good quality builds fast AF, but not a photographer tool.
02-19-2015, 01:52 PM   #8
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QuoteOriginally posted by igabc Quote
I am going to return this lens. I would buy it for just 100 USD. Not more than that and definitely not for 280.

I don't even consider it a photography lens. It's good as a molecular, to get closer to subjects, good quality builds fast AF, but not a photographer tool.
Really? I love mine. Here's some examples of work produced from the 18-135:

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/179869-da-1...at-can-do.html

Here's a random page:
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/179869-da-1...can-do-51.html

02-19-2015, 02:00 PM - 1 Like   #9
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QuoteOriginally posted by igabc Quote
Yes I know how to use the autofocus and of course I give it the chance, even though only in fast situations. I like manual focus. You take that away from me, I feel like being makin love to a woman without kissing her. You know what I mean.
I really dislike the feel of the 18-135 for manual focus. It is a great lens and I use it all the time in AF but detest it for manual focus.
02-19-2015, 02:06 PM - 1 Like   #10
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QuoteOriginally posted by crewl1 Quote
I really dislike the feel of the 18-135 for manual focus. It is a great lens and I use it all the time in AF but detest it for manual focus.
Ahhhh - sorry now I understand. Manual focus primary use lenses are different. I LOVE them but not with my K50. The stock focusing screen stinks for manual focus and I still haven't found LiveView to be consistently better than focus confirmation even with focus peaking. Frankly I guess at some future point I need to try one of the split prism focusing screens but the hassles of that setup are enough to keep me from just jumping in feet first.

For great feeling manual focus I'm not sure what current model zooms to recommend. The SDM based DA* lenses have an odd feeling to them when manually focused - the lack of a positive stop at either end is one of the things that makes me a little cool towards using them in full time manual mode. The older FA lenses are so so but I think the K and A series might be your best bet. Best of all they are generally cheaper (not all models) than the equivalent DA/DA* models.
02-19-2015, 09:00 PM   #11
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Today I tried to take the new K3 "out for a ride" in the freezing 16F (-9C). I couldn't resist. But I took only few shots then ran back home with my hands almost frozen. I also took some pictures to compare the 18-135 to the vintage SMC 135. Using vintage glass is not easy (exposure) but that old focusing ring is amazing. Much more precise, easier to work with, softer...love it!

the chromatic aberration on the 18-135 is really bad (at full zoom). I have also noticed some ghosting effect on tree branches that really worry me. I will post some samples soon. Hopefully it's not a sensor defect.
02-19-2015, 11:45 PM   #12
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QuoteOriginally posted by igabc Quote
Today I tried to take the new K3 "out for a ride" in the freezing 16F (-9C). I couldn't resist. But I took only few shots then ran back home with my hands almost frozen. I also took some pictures to compare the 18-135 to the vintage SMC 135. Using vintage glass is not easy (exposure) but that old focusing ring is amazing. Much more precise, easier to work with, softer...love it!

the chromatic aberration on the 18-135 is really bad (at full zoom). I have also noticed some ghosting effect on tree branches that really worry me. I will post some samples soon. Hopefully it's not a sensor defect.
Samples would be good. Don't see either of those issues with mine and I would expect an old lens to have more issues on digital vs one optimized for it.
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