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09-21-2012, 12:17 PM   #1
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Help me decide

I came to the point where I have to choose upon an upgrade to the kit lens on my beloved Pentax K-10.
I have narrowed my choice to 2 lenses -
SMC Pentax-DA 17-70mm F4 AL [IF] SDM
SMC Pentax-DA 18-135mm F3.5-5.6 ED AL [IF] DC WR

SMC Pentax-DA 18-135mm F3.5-5.6 ED AL [IF] DC WR

The most important factors for me are the image quality and mainly sharpness.
I saw many sample images


Pentax SMC DA 17-70mm f/4 AL [IF] SDM - Review / Test Report

and here


I find it difficult to choose between the two, even tough I lean towards the 17-70.

Any comments?

09-21-2012, 12:35 PM   #2
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From what I've read the 17-70 is sharper, but I chose 18-135 for WR. It replaces the 16-45 as short walkaround zoom for me.
09-21-2012, 12:49 PM   #3

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If sharpness is paramount, get the Tamron 17-50 and a 90/105mm macro, which are almost all sharp lenses.
09-21-2012, 02:47 PM   #4
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I recently had to make a similar decision. I went with a Tamron 17-50 due to the sharpness and the constant f/2.8 aperture. Each of the lenses you are considering has its pros and cons, but in the end they are all a better option than the kit lens.

09-21-2012, 02:53 PM   #5
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Maybe the best way to go about this, is to ask, what things do you dislike about the kit lens? The 17-70 will give you some more speed (aperture) and a little more focal length, whereas the 18-135 will get you a lot more focal length but no speed improvement. I guess those things are obvious just based on the specs. But the reason I ask is that there are other options too, like buying one or two primes instead of another zoom.

I personally bought the 18-135 because I already had the 18-55 and couldn't see the need for a similar zoom range in the 17-70. The 18-135 range is really great for walk-around use, and I rarely need more than 135mm. And for low-light use I have some primes.

Edit: OK, I see you already mentioned sharpness. Everyone seems to say that ... who doesn't want to take sharp pictures after all. If that is your main criteria, then the 17-70 does seem to have a better reputation for sharpness across the whole image. Most tests (including my own informal tests) show that the 18-135 is sharp in the center, not so much at the edges. There are other threads debating whether this is a problem or not. For me, the emphasis on center sharpness at the expense of edge/corner sharpness is not a problem, in fact it is sometimes preferable.

Last edited by Tanzer; 09-21-2012 at 02:59 PM.
09-21-2012, 02:59 PM   #6
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I have the tamron 17-50 but actualy wish i bought the pentax 17-70 lol The tamron is without doubt the sharpest available though. The 17-70 is still a good lens. Certainly the best from Pentax. Your best looking on photozone and checking the pros and cons yourself.
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09-21-2012, 03:06 PM   #7
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I recently bought the 17-70 from a forum member. Although I primarily shoot primes the Da 17-70 has become one of my most used and loved lenses. A 2.8 lens is nice when needed, but I rarely shoot wide open so the Da lens fit for me.
Good luck in deciding!
09-21-2012, 03:27 PM   #8
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I second the 18-135mm. Its AF is faster and it gives you more reach. I used it to shoot all of photokina and had no problems at all...

The only thing it isn't good at, IMO, is portraits. But neither is a F4 zoom!

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09-22-2012, 11:38 PM   #9
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I came upon this post

What is your opinion experience in this matter?
09-23-2012, 06:37 PM   #10

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QuoteOriginally posted by ronyzmbow Quote
I came upon this post

What is your opinion experience in this matter?

With film, lens color rendition differences were significant in critical work. Modern lenses have less difference and digital is easy to color correct. If Sigmas have a color-cast rep, it is that they are a bit yellow or warm.

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