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05-26-2011, 06:11 PM   #1
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ephotozine review of DA 18-135mm WR

Just published today! I'm excited about getting this lens someday; the photozone review scared me a bit but I'm glad this one is a lot more positive.

SMC Pentax-DA 18-135mm f/3.5-5.6 ED AL [IF] DC WR Lens Review

05-26-2011, 08:55 PM   #2
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In my opinion this review has nothing very surprising given the other tests, reviews, and user opinions we've seen. With a compromise lens like this, some people just tolerate the compromises better than others. There are some errors in the charts--i.e. the MTF50 at 70mm lists the same aperture value twice, and the MTF50 at 135mm lists the first entry as f4 (impossible--must be f5.6).

Speaking of which, I find the 135mm f5.6 (or f4 as their error puts it) plots to be suspect. The MTF20, MTF50, and CA values are wildly divergent from the rest of the tested values. For instance, the part-way and corner MTF's are higher than the center (only time this comes close to happening), and considerably higher than the values they reach when stopped down. In my opinion, the lens was "misfocused" for this 135mm f5.6 test, and that is giving us the aberrant values (also thus note the aberrant distortion value).

That having been said, those "aberrant values" suggest to me that the issue is not mere softness at 135mm in the edges/corners, but rather significant field curvature at 135mm. For with this "misfocus," we get good part-way and corner performance at the expense of center sharpness (which here is pretty near even with the rest). So the field curvature is well worth noting (photozone gave no clue to this), as that may not be as field-relevant to shooters as mere softness. As always, lenses exhibiting enough field curvature are harder to test for MTF, as of course it is up to the reviewer to choose what value to bias (center or off-center), and people should thus take those numbers with a little more caution than usual.
05-26-2011, 08:56 PM   #3
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The corner sharpness (particularly at higher focal lengths) appears to be a bit disappointing to me.
They don't really say anything about it - or am I reading the MTF graphs wrong?
Would imagine it would be very noticeable if photographing square on subjects.
So if you are after corner to corner sharpness then maybe not such a good fit.

Still a nice focal range and WR is great.
05-27-2011, 07:09 AM   #4
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I would prefer the 55-300 on the similar focal lengths that the 18-135 covers. my complaint is, Pentax should/could have just atleast made the lens as good as the 55-300. I dunno, although the 18-135 is quite good to be fair, it is also underwhelming at the same time, especially for the premium that Pentax is asking for it.

05-27-2011, 07:43 AM   #5
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Yeah, I'm struggling over whether to buy this zoom lens for the price (Adorama is selling it for US $429 right now, lowest I could find it brand-new). I don't have a WR body (I have a K-X) so the fact that the lens is WR isn't the biggest consideration for me. However, it would be nice to have the lens in my collection so that when I do eventually step up to a K-5 (or other WR body), I'll already own a WR zoom lens. Small size and light weight are very important to me, so that's why the 18-135 appeals to me a lot. Also I like the lens' quiet DC AF motor (but worried about whether it will be any more reliable over the long term compared to SDM?). I don't think I need longer than a 135mm range for most of my shooting purposes. I just want a single lens for travel, so that I don't have to swap my primes all the time. I'll accept the compromises that the 18-135 represents-- where image quality takes a back seat to convenience. Curse you, LBA!
05-27-2011, 11:29 AM - 1 Like   #6
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I have this lens and it's simply a great travel kit - WR, DC focus, compact and super convenient range. Color and contrast are very good too. You really have to use it to appreciate it. I'm sad that people dislike this lens simply because of the poor border performance in the test charts. For most people, this lens won't disappoint in real world use.
05-27-2011, 12:34 PM   #7
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Thanks, @spesholized, for the positive recommendation from an actual owner of the lens-- it definitely helps feed my desire to own one soon! I think people dislike the lens in part because of the disappointing optical performance relative to the high price. If the lens were in the US $300-range, I think many people would be jumping on it for the WR and DC features alone. Or, lots of people already own a 18-250 zoom, or 17-70, etc, so it's hard to justify another zoom that covers some of the same range.

As for me, I have the kit lenses DA-L 18-55 and 50-200, so in order to get a superzoom for travel purposes, I can choose from among a used 18-250, 17-70, or 18-135. Because all three lenses are over US $400, it comes down to which one do I want to spend my money? I think 17-70 does not offer enough reach, so I'll rule that one out. That leaves 18-250 versus 18-135, a tough choice when one considers the differences: extra reach versus WR, zoom creep versus silent AF, very good IQ versus "average" IQ, used copy versus new under warranty, tried-and-true versus unproven, etc etc.

I am an owner of the DA-L 50-200, so I'm no stranger to owning lenses that do not receive unanimous praise. But for some of the things that matter most to me (physical compactness and lightness of the lens), the 50-200 is the right choice for me even though I know the 55-300 is optically superior. I bet I'll be feeling the same way if and when I acquire a DA 18-135...
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