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08-01-2014, 08:18 AM   #1
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Zoom Lens Upgrade

I am looking to upgrade my kit zoom lens. Currently have the weather resistant version of the 18-55. However, I more often use my old Pentax A lenses. I am specifically looking for a better travel/walk around AF zoom lens and would also like to have a bit more range on the long end. I am considering the Pentax DA 18-135 ED AL or the Sigma 17-70 F2.8-4. The range 17-70 would probably cover most of my walk around needs. I have looked at the forum's reviews for these two lenses. All comments and suggestions appreciated.

08-01-2014, 08:38 AM   #2
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Have you checked the Pentax DA 17-70 too? That's also a well-regarded lens.
08-01-2014, 08:49 AM   #3
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The 18-135 is a great walk around lens. My wife upgraded to it from the 18-55 and the IQ difference was easily noticeable without pixel peeping. The Sigma 17-70 is also highly regarded though I have no experience with it. The choice would be between a WR lens with longer focal length that is somewhat slower and the Sigma without WR and shorter focal length but somewhat faster. Which do you value more? WR? 135mm? f/2.8?
08-01-2014, 08:55 AM - 1 Like   #4
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DMD,

I just finished the 18-135 WR review for Pentax Forums (sorry, it hasn't been officially published yet otherwise I'd link to it), and in it is a significant amount of attention spent comparing it to the 17-70 F2.8-4 "C," widely accepted as the best of the 17-70 variants from any brand.

Between the two, the bottom line is this:

Physically

+ 18-135 is weather sealed
+ 18-135 has significantly longer reach
+ 18-135 is smaller, lighter, and uses smaller filters
+ 18-135 is just as fast at AF (perhaps a hair faster?)
- 18-135 does not have distance markings for manual focusing
- 18-135 has a really unpleasant manual focus ring
+/- 18-135 only lags 17-70 by 1/3 stop for max aperture throughout similar zoom settings, 2/3 stop at most for a small amount (F5.6 on the 18-135 doesn't start until after 70mm)

IQ Wise

= Indistinguishable bokeh between the two at similar apertures
= Nearly indistinguishable center sharpness between both for shared zoom range (if there is a slight edge, it goes to the 17-70, but you have to be looking for it)
- 17-70 maintains excellent edge sharpness (especially after 2/3 stop closed down) while the 18-135 is very disappointing
= Just as easy to isolate your subject through shallow DOF

Doing the review made me realize one thing - unless you need edge to edge sharpness, I couldn't find a legitimate reason to skip the 18-135 WR in lieu of the 17-70. Of course, if the Sigma were weather sealed, that would be a game changer in this comparison, but it isn't. If you have a weather sealed camera, then imo it behooves you to get the 18-135 WR.

These shots were taken with the 18-135:













Hope this helps.

-Heie

EDIT:

I forgot to mention the pseudo macro abilities. The 17-70 offers .29 (1:3.4) vs the 18-135's .34 (1:4) max reproduction. Doesn't seem like a lot, but it is. The only major issue, though, is that at minimum focus distance, the 17-70 is literally within an inch (2.5 cm) of touching your subject. It was extremely difficult to use the 17-70 in that situation I found.

As soon as the full review goes live, I'll be sure to link to it.


Last edited by Heie; 08-01-2014 at 09:53 AM.
08-01-2014, 09:14 AM   #5
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The 17-70 also focuses closely. Don't know about the 18-135.
08-01-2014, 09:53 AM   #6
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QuoteOriginally posted by SpecialK Quote
The 17-70 also focuses closely. Don't know about the 18-135.
I believe the 17-70 does about 1:3 while the 18-135 stops at about 1:4. So the Sigma gets closer, but the Pentax isn't bad either.
08-01-2014, 10:19 AM   #7
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Here's another vote for the 18-135.
Since I got one I don't think my Sigma 17-70 has been out of the cabinet
08-01-2014, 10:56 AM   #8
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QuoteOriginally posted by DMD Quote
I am looking to upgrade my kit zoom lens. Currently have the weather resistant version of the 18-55. However, I more often use my old Pentax A lenses. I am specifically looking for a better travel/walk around AF zoom lens and would also like to have a bit more range on the long end. I am considering the Pentax DA 18-135 ED AL or the Sigma 17-70 F2.8-4. The range 17-70 would probably cover most of my walk around needs. I have looked at the forum's reviews for these two lenses. All comments and suggestions appreciated.
The Pentax DA 17-70 is very versatile, very good IQ. Got mine used a few years ago at KEH. My work horse small studio lens and a good walkabout choice.

Disclaimer. I live on manual exposure, so constant aperture is important to me. If the Sigma was, I'd have looked at it. My Sigma 100-300/4 is a great lens.





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