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12-02-2013, 12:30 PM   #1
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Help Get My Head Around 18-135 WR

Hey forum, I could use some help and advice regarding my 18-135 WR lens. I bought it with my K5ii after reading all of the reviews, advice and comparisons between it and the 18-55. I've used it a fair bit, but am really more of a prime shooter and have several that I would rather use when given the choice.

I will say that the 18-135 is extremely well built. Focus is fast and silent and it handles beautifully. And I value it for the WR. It's my only weather resistant lens and I live in Seattle, so I must have one. If not, I'd have lots of other choices. I do have a manual push/pull Tokina zoom which kicks the crud out of it on sharpness and gives me more long end reach.

This weekend, I was bored and testing primes vs each other and shot the WR zoom at that focal length for comparison. At some FLs and apertures it was close, but it was never as good. That's to be expected. At 24mm where I consider it to be very good, it dramatically underperformed. I retested, but manually focused in LV and it did much better, as good as my prime in fact.. That tells me that the focus is missing, by a lot. It is backfocusing, to be specific. The first test was done on a tripod at a static object in good light, so fairly ideal circumstances for AF.

I read a lot about AF adjustment, which seems less than idea for a super zoom. If I dial it in at 24mm, it's likley to be off at 70, right? It seems to focus better at 50, which is probably closer to where I would want to calibrate the adjustment or may be 70. I'll spend more time with that, but I suspect that an adjustment in the middle of the range is not going to make it more reliable overall. Any thoughts or advice? Having it be essentially a 50mm prime, it's suddenly not compact, light and is extremely slow. I need for it to function useably well over most of the range.

My other thought, which defies all Pentax Forums advice is to perhaps sell it and buy an 18-55 WR zoom and use the money on a prime at a range where I'm currently lacking. I want a WR walk around zoom, but the one I have is not making me as happy as other choices in my bag, so why not have a cheaper one and reallocate some of that budget to a lens that might make me happier? The 15-55 WR also has a 52mm filter thread, which matches other lenses I own, which will enable me to share filters. The 18-135 is currently an odd size for me, so I haven't bought any filters for it.

The 18-135 is very compact for what it is, when you start comparing it to similar zooms. Again, very well engineered. The 18-55 is significantly smaller and lighter, though. It also seems that the tighter the zoom range, the easier to dial in AF adjustment, right?

The silent focus on the 18-135 is amazing, but it's too slow to shoot at something like a concert and I can use something like my DA40/2.4 or my manual focus 55/1.8, for example, which is dead silent, of course. Outdoors at a picnic or street photography, which is more of an application for my WR zoom, a little focus noise is not nearly as big of a deal.

So a) is there some good advice for dialing my existing zoom in and b) Am I the only one who has ever considered downgrading from the 18-135 to the 18-55? Am I crazy to think such things?

I see some nice sample photos and happy users of the 18-55 lens, but whenever the question of comparing the two comes up, we as a group are never kind to the 18-55.

Thanks in advance for the advice.


Last edited by troika; 12-02-2013 at 12:37 PM.
12-02-2013, 12:38 PM   #2
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Could it be that there's something wrong with your 18-135mm? Personally, I'd never downgrade to a lens that goes bzzt bzzt while focusing, but that's just me The 18-55 is certainly a bit smaller than the 18-135.

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12-02-2013, 12:48 PM   #3
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While it's not as sharp as my FA100 Macro shooting the same subjects, my copy is no slouch. I'd suspect something is wrong - is the lens still under warranty?
12-02-2013, 12:51 PM   #4
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QuoteOriginally posted by Adam Quote
Could it be that there's something wrong with your 18-135mm?...
Well, it's certainly missing focus, but I don't think that constitutes "something wrong" and I think I'm supposed to be able to adjust that. I haven't tried yet, but will.

Generally I think it's a really good lens. At 24mm for example, I think it's great focused to infinity and when I manually focused it in my test it was great. As good as the prime I was testing. i could see it actually being better at some things because of the coatings and aperature blades, but (at least in this one test), it's not going to be "sharp" relying on AF.

I've always found it less than crisp at the other end of the zoom range and that seems to be a consensus.

If I can fix this with some AF adjustment and get really crisp usable images over the middle 70% of so of the zoom range, I'd be happy. I'll print a test chart out and work on that. I recall a thread where someone was very blase about this lens and consented to send it with their camera to Pentax and was overwhelmed by the result when they got it back. I'd be willing, but I couldn't find that thread searching for it and wasn't sure I was remembering correctly.

12-02-2013, 12:55 PM   #5
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QuoteOriginally posted by TER-OR Quote
...is the lens still under warranty?

I don't know, good question. How long is the warranty? I (EDIT: I bought it last February) and I bought the extension from Adorama with my kit.

You and Adam seem to be on the same page. I just wasn't thinking that this was a defect, so much as a product of a) needing a focus adjustment and b) things characteristic of a super-zoom.
12-02-2013, 12:58 PM   #6
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Nah, it should be acceptably sharp mid-range in particular. The 135 is a little soft on mine, but up to 100ish it's nice.
Check your paperwork - and get it calibrated if you can.
12-02-2013, 01:01 PM   #7
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I've used the 18-135 a lot with my K-30 and did the focus fine adjustment on it. I found it to vary between -1 and -3 throughout the zoom range and at different apertures, which isn't much variation. I set it at the midpoint of -2 and it is perhaps not perfect but certainly good enough at that setting over the whole range.

What range of fine adjustment are you having to dial in over the whole range of focal length. If you need a very wide variation then maybe the lens is faulty.
12-02-2013, 01:03 PM   #8
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I think with any consumer zoom you are going to compromise IQ at some focal lengths.

I like the 18-135 for it's compactness, convenience and WR, as I use it as my 'outings with family' lens and never have to worry about what we encounter, or stopping to change lenses.

If you think of it that way it may not matter that the IQ is less than prime quality at some focal lengths.
Bring out the primes when you need them.

You can try doing a focus adjustment and see how it responds, you can always change it back if it makes things worse and then consider the warranty claim.

12-02-2013, 01:04 PM   #9
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QuoteOriginally posted by lister6520 Quote
...

What range of fine adjustment are you having to dial in over the whole range of focal length. If you need a very wide variation then maybe the lens is faulty.
I don't know, I haven't tried yet. I read about it this weekend and decided that I needed to print out a chart and wait for some sunlight, since it said not to adjust under tungsten light. I certainly need to try focus adjustment and will work through that process before I do anything else.
12-02-2013, 01:39 PM   #10
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I have the 18-135 as my only WR lens for use with my K5-II. For me it performs fine for when I need it, but my primes are sharper with better color. But for a walk around lens when it is not safe to change lens I am glad I brought it with me. On a recent trip to Yellowstone it was mostly the only lens I would use, because of the blowing wind & sulfur, mist & water spray and rain. We were traveling via motorcycle/sidecar so most of the time there wasn't any safe place to be changing lens.
It was kind of cool for us city slickers to be sitting on/in the bike & sidecar, stopped in the roadway while several bison wandering past only a few feet away. Sure glad we left our little barking dog home.
12-02-2013, 01:49 PM   #11
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Yeah, so just to be clear. I'm sold on having a zoom in my bag and WR is one of the reasons I am with Pentax. There is no question that I will own a WR zoom for walk around and circumstances to the ones being described here. I've used mine quite a bit under similar circumstances. If I manage to get home in time today, I'll try to test and adjust my AF settings and see where it leaves me.
12-02-2013, 05:20 PM   #12
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I made it home in time to do a little testing outside in natural light. I didn't have a test chart, but used a pencil stuck in a lavender hedge and a leaf on a very bumpy sidewalk; camera on a tripod, etc.

It's definitely backfocusing through most of the range, I adjusted up to +7 and started getting some good hits in the ~55mm range, I need more (and probably more structured) testing to determine what that does to the focal lengths at either end. It's possible that it's now front focusing on the wide end and still back focusing a bit on the long end, which I think makes sense...but I have to think about it and do more testing.

So, I suppose that means that this lens has always needed an adjustment and I shouldn't read too much into the fact that since I hadn't made it, I was never overwhelmed with the results. I'll invest in working through this and will print or buy a chart to do it properly.

Based on what I've said here, do those of you with more experience still think this is "something wrong with my copy" issue or just the normal adjustments that AF lenses need?

Without naming other lenses to compare it to, is it fair to say that zooms with shorter overall range tend to be easier to dial in across the range? in other words, a AF +/- adjustment applied to a 16-45 lens might reasonably be more consistent across it's range than on say an 18-250? (Picking 2 lenses that I don't own and don't mean to invite discussion on specifically)
12-02-2013, 05:26 PM   #13
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I don't know that there is a rule, I think it may come down to the individual unit and sample variation.
I had a 17-50 from another manufacturer that had BF on one end and FF at the other end on my camera, and the reviews say it is a well regarded lens.
My 18-135 has not needed any adjustments at all.
I have an 18-250 that is fine as well across its range.
12-02-2013, 09:06 PM   #14
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If it won't calibrate across the zoom lens, submit a warranty request though Pentax. They'll fix it in a few days and it'll come back close to perfect, I'm guessing.
12-02-2013, 09:21 PM   #15
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That's starting to feel like a great choice. Any advice on how to initiate the procedure?
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