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03-17-2012, 04:16 PM   #16
philbaum's Avatar

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Location: Port Townsend, Washington State, USA
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I'm looking at these standard zooms as well but for a different reason. I shoot promos and rehearsal shots for a live theatre (as in plays), occasionally there is a need for wide angle shots, and i have no zoom that covers that area below my Tamron 28-75f2.8. I usually get by via putting on my DA21, but then i'm stuck there if i want more FL than that, so i have to change out the lens again - major pain in the ass.

I've looked at way too many things on the internet for the last 2 days in comparing Sigma 24-70 f2.8, Sigma 17-70 f2.8-4 HSM, Sigma 17-70 f2.8-4.5(older model without hsm) and the Pentax 17-70 F4.

None of the shorter zooms out there, i.e. Tamron or Pentax 17-50 f2.8s thrill me because they don't have enough overlap into the 70 FL area which is frequently needed even when one can roam the seating area as much as one wants. The upcoming Pentax 16-85 on the road map makes me salivate, but i'm tired of waiting for a "possible" lens.

After all my comparison effort, Pentax 17-70 F4 looks like the best out there for what i need. It has several good characteristics:

A. Even said this about it:
The Pentax DA SMC 17-70mm f/4 AL [IF] SDM is undoubtedly the most
desirable standard zoom lens in the current Pentax lens lineup. The resolution
characteristic is very good without any significant weakness. The vignetting
and distortion are about average for a lens in this class. The lateral CAs are
relatively well-controlled although you may spot some traces in field
conditions when using wide-angle settings. The quality of the bokeh
(out-of-focus blur) seems to be very fine albeit limited compared to fast prime
lenses naturally. Contra-light situations are handled fairly well with
comparatively underdeveloped ghosting problems. Typical for most Pentax DA
lenses the build quality is on a very high level. The fast and near-silent
ultrasonic AF is also a very welcome new feature. All-in-all a very harmonious
package selling for a very fair price of around 480€/US$
B. If you go to the site and compare MTF figures between the available Pentax 1770 test (done with K10 at 10 mpx) with the new Sigma 1770 HSM (no test yet available on Pentax mount, but there is one done on the Nikon D7000), you'll find that the new Sigma supposedly is a sharper lens than the Pentax 1770 F4. But i think thats an incorrect assumption to draw because of the different sensors. For example, if you look at's retest of the DA 40 (originally done on a K10 with 10mpx and more recently repeated on a K5) you'll find that the MTF resolution increased by 19% or therabouts (i didn't do a comprehensive check). So applying 1.19 to some of the older Pentax 1770 numbers shows that its everybit as sharp as the Sigma 17-70 at F4 (f2.8 is kind of soft so it wouldn't be fair to use it for any comparison - duh )

C. Then i went to the interesting blur chart on and compared the flatness of that blue blanket 3-D chart between the Pentax 17-70 F4 and the Sigma 17-70 f2.8-F4 HSM. The Pentax 17-70 blue blanket lies much flatter and spends more of the time in the 1-2 Blur unit area than the Sigma lens which occasionally sneaks up to 3 blur units.

D. Looking at the user reviews on PF, they suggest that users were impressed with the quick focusing nature of the sdm on the Pentax 17-70, apparently relating to the short 45 deg. throw of the focus ring. The sdm does'nt concern me because i've had 2 sdm lenses for 3 years with no problem from either. Further, Adam's recent poll on sdm shows a pretty remarkable dropoff in problem reports for the last 2 years. Some users with older Pentax 17-70 lenses complained about the sharpness of the lens, even returning 1 and getting back a sharper one, some other users said it was remarkably sharp, one saying that it was better than any other brand they had tried for that type zoom.

E. The down side for both lenses is that they are pretty sizable. If i remember right, the new Sigma was 3.9 inches long by 3.2 in. diameter while the Pentax is 3.7 in long by 3.1 in. diameter. Sigma weight 19 oz and Pentax weighs 17 oz.
Those are the retracted sizes by the way, extended they are much longer.

I'd love to wait for the new Pentax 16-85, but it'll probably be selling for far more than the current $479 of the Pentax at BH. I think i'll spring for it now, unless there are convincing replies on the OP's thread that the Pentax version is not the way to go. (By the way, I've seen good comments on both the older and newer Sigma 17-70s, so i'm sure a good case can be made for those as well )

Last edited by philbaum; 03-18-2012 at 04:33 PM.
03-17-2012, 04:21 PM   #17
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WWWench's Avatar

Join Date: Mar 2009
Location: Palm Springs, CA
Posts: 66
This is my belt-loop travel rig, considering most factors with airlines, security (searches, me, camera gear) the 'strap cut thief ' too. Art museums allow since it looks toyish.
TY atekant for the tip for my extra pancakes. I carry a monopod as well, walking stick and good weapon if needed.
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03-18-2012, 07:44 AM   #18
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If you want compact and fast apertures then ditch a big all in one zoom and grab and DA15 or 21, an M50f1.7 and a M100f4Macro or M100f2.8nonMacro. You don't have WR but you have all of the bases covered and these are excellent lenses while being small.

It's the same basic kit that I have but I add in a few others... like I want the 18-55 WR (don't have yet) if it's going to be wet, maybe I'll throw in the M28f2.8 or use my DA40 in place of the M50. I also have a M135 instead of either of the M100 lenses but I would like to get the macro or upgrade all the way to DFA 100WR.

One thing that hasn't been mentioned yet but you don't need fast apertures with wide angles because you can get reasonably good photos at 1/focal length unless there is motion. but you have the K-5 with a lot of iso which is better than using a fast aperture anyway.
03-18-2012, 02:39 PM   #19
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Laurentiu Cristofor's Avatar

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Location: WA
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QuoteOriginally posted by atekant Quote
I am looking for the one perfect travel lens to take along with my K-5.
"Travel" is too generic - will you go to a city, where you'll have more use of wide to normal focal lengths, or will you go to Africa looking for wildlife, where you'll want a telephoto. There is no lens that can properly cover both those scenarios, so you can drop the idea of "one lens to rule them all" from the start.

Better think of what kind of travel you will be doing, what kind of focal lengths you will be using, and what kind of optical performance you are looking for and then find the best compromise. You'll not find perfection for sure, just a compromise that will suit you - and *you* is the keyword there - you might be the only one willing to live with that compromise.


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