[jwcjrccc]

I have a Pentax DA 16-45 which I often use for photos of buildings in small towns. I use the wider angle portion of the lens frequently. DXO Mark lists the Sigma 17-50 F 2.8 as the best zoom lens for the Pentax K-5 II, and the Pentax DA 16-45 as the second best zoom lens for the K-5 II. Has anyone used both lenses, and if so, was the image quality of the Sigma much better than the image quality of the Pentax 16-45? Is it worth spending approximately $300 to purchase the Sigma lens if one already has the Pentax 16-45? Also, has anyone used both the Pentax 16-45 and the Pentax 18-135? If so, is the image quality of the 18-135 noticeably inferior to the image quality of the Pentax 16-45 at the same focal lengths? Oh, the problem of being on a budget...

[fredralphfred]

Can you tell us what you're unhappy about with the photos from the 16-45? If you know of something specific you think the Sigma might do for you, it would be a bit simpler for someone who has had both to let you know. I've had neither ('though I do have the 18-135). If you're using the wide end consistently, would you not be better off overall using something like the HD 15 or the Samyang 16?

[jwcjrccc]

Can you tell us what you're unhappy about with the photos from the 16-45? If you know of something specific you think the Sigma might do for you, it would be a bit simpler for someone who has had both to let you know. I've had neither ('though I do have the 18-135). If you're using the wide end consistently, would you not be better off overall using something like the HD 15 or the Samyang 16?

Well, you have asked a very good question, The JPGs taken with the 16-45 look acceptable, but I am embarrassed to say that I'm so far behind in processing photos, that I've processed few of the raw files taken with the 16-45. I should process a number of the raw files taken with the 16-45 and determine whether I'm satisfied with them. Until I do that, there's really no point chasing after a lens that might produce marginally better photos. You've made a very good point. I should be able to answer your question before buying another lens. Thanks.

[fredralphfred]

Well, you have asked a very good question, The JPGs taken with the 16-45 look acceptable, but I am embarrassed to say that I'm so far behind in processing photos, that I've processed few of the raw files taken with the 16-45. I should process a number of the raw files taken with the 16-45 and determine whether I'm satisfied with them. Until I do that, there's really no point chasing after a lens that might produce marginally better photos. You've made a very good point. I should be able to answer your question before buying another lens. Thanks.

Well, the reason I asked is that I purchased too many lenses this year, then when the K-50 dropped, I got it in a kit with the 18-135. I've had so much fun with the 18-135, I almost don't care that I've got better lenses sitting at home. It's nice to know I do if I think of something specific I want to do, but I really, really like that lens. If I'd gotten that lens with my K200D 7 or 8 years ago, I'd probably never have purchased another.

[normhead]

Also, has anyone used both the Pentax 16-45 and the Pentax 18-135? If so, is the image quality of the 18-135 noticeably inferior to the image quality of the Pentax 16-45 at the same focal lengths?

On Photozone they appear to be very similar, with the 16-45 being better wide open, but stop down virtually identical with the 18-135 being better corrected for CA. If I had the 16-45, I'd be really tempted to go with the 55-300 for my next lens.

The Sigma 17-50 and Tamron 17-50 are both a touch better, but comparing images I doubt you'd see much difference. assuming both were good copies of the respective lenses. But why duplicate what you already have?

[audiobomber]

You will probably be interested in these test images. They are posted at full resolution. Click on the magnifying glass, then move the slider in the popup to pixel peep.
https://plus.google.com/u/0/photos/100586096103361553535/albums/561531801814...LOD9LjmoOKTlAE

The 16-45mm is a stronger lens than the 18-135, but because of the 18-135's range and weather-resistance, the 16-45 stayed home more often than not.

I bought the Sigma 17-50mm early this year and eventually sold the 16-45. I had no clear preference in IQ between the two standard zooms. Sometimes the 16-45 looked better, sometimes the 17-50. Sometimes 16mm is more important than 50mm. The Sigma has noticeably better CA performance. Due to the extra stop, the 17-50mm is more versatile. I can get away with a zoom in some cases where I would previously have used a prime, because f4 is too slow. I was a huge fan of the 16-45 for many years. I feel the 17-50mm is a worthwhile upgrade due to the extra stop.

I use the 18-135mm when I want WR and all-purpose range. I rely heavily on weather-resistance. If you don't have a WR lens, it is well worth considering. The 17-50mm can substitute for primes, it is that good, and pairs nicely with another lens, e.g. 100mm f2.8 macro, 55-300 f4-5.8 or 70-200 f2.8.

[mgvh]

When I was just starting out 4 years or so ago, I bought a 16-45 from someone here on the forum to replace the 18-55 kit lens. I wasn't particularly impressed with the 16-45, but I didn't know better at the time to realize that it was decentered. I sold it on ebay (providing pics showing the effect), not only because it was soft on the one side, but also because I found that 45mm was simply too short, and I was constantly switching to the DAL 55-300. So, I replaced it with the 18-135 and have been very happy. My question is whether the 16-85 would suit me better. I would like the extra 2mm on the wide end and the slightly better quality at the wide end the 16-85 apparently can supply, but I'm not sure I'm willing to give up the convenience of that 85-135mm at the long end.

[One3rdEV]

jwcjrccc- I think your decision to take a closer look before jumping is a good idea. I do not have the 16-45mm so I cannot speak to that lens, but I've had the impression it is a good lens. I do own both the Sigma 17-50mm F2.8 and the Pentax 18-135mm F3.5-5.6. A quick look at Photozone.de indicates that the 16-45mm has slightly reduced barrel distortion and pin cushioning effect than the Sigma 17-50mm (by up to about 0.5%). This might be a slight advantage for buildings as subjects. The Pentax lenses will tend to have that bit more contrasty look which is somewhat signature for Pentax. The Sigma has a little less contrast and per my personal opinion a bit closer to real-life color rendering. When I compare images with the subject still in front of me- I tend to prefer images taken with the 17-50mm. This is based on the perspective created from my former life shooting transparency film with Zeiss medium format lenses. However, when I look at DSLR images across the web (e.g. when I am not comparing to the actual subject and am just considering the image as it is rendered)- I totally love the Pentax look! The Sigma on my K5 classic is capable of some very fine resolution. One thing I don't care for with the 17-50mm is that its large lens diameter of 77mm frequently bumps into my wife when my camera is hung over shoulder and we are walking hand-in-hand (but at least it has a zoom lock). The 18-135mm at only 67mm lens diameter is much better in that regard- except it doesn't have a zoom lock and results in zoom creep. For the purpose of family activities or vacation photos I am very pleased with the 18-135mm. I believe its 'flawed' characteristics of sharp center and notably softer edges work fine for many of these types of images and sometimes contributes to a 3D effect. It handles flare well and I believe much better than the Sigma. Photos of buildings (e.g. an old fashioned structure surrounded by its environment near the edges of the frame) could look good with the 18-135mm. In this case its characteristics would tend to isolate the subject. However architectural work where the impression of center image sharpness might be desired all the way to the edges of the frame would very likely not be well suited to the characteristics of the 18-135mm.

---------- Post added 07-11-15 at 12:59 AM ----------

LOL - well by the time I got the above lengthy reply completed, a few more members had posted. So I'll add a few more comments regarding some points made by those.

I've also have had lots of fun with the Pentax 18-135mm which was purchased several years after the Sigma 17-50mm. In fact the Sigma sits on the shelf most of the time while the 18-135mm is frequently in use. This is because the 18-135mm is so well suited to the situations I find myself shooting in the most often… family activities, WR for kayaking etc.

I also find the auto everything digital age in general to be a more finicky and less consistent mistress than the old film days (e.g. autofocus, exposures, lens calibration and lens performance).

The one time I did a side-by-side comparison of the 18-135mm and 17-50 F2.8 together on a tripod I was surprised to find the Sigma RAW performed slightly better in regards to resolution, color graduation and even 3D effect. I, similar to Norm, tend to be an optimistic fan of the 18-135mm and I figured that the 18-135mm at its best should be able to give the Sigma EX DC a run for its money. Nevertheless, I'm still a fan. And neither will be sold. Of course more than one test and 2 images should be made in order to conduct a fair assessment and I also don't know where my samples fall within the distribution of lens performance potential.

[jumbleview]

I have Pentax 16-45 for about 2 years and sigma 17-50 2.8 EX HSM (no OS) for couple of month. Mechanically sigma is better. At 17 mm it is shortest. Pentax is longest at 16 and because of that it is not possible to use wide open with in-camera flash. With sigma in-camera flash is OK for all zoom range. Regarding the sharpness they both good, sigma probably a little better especially if you compare at max zoom. Sigma focuses faster. But colors from Pentax I like more, maybe I just did not get used to sigma yet. Quite possible it could be improved in post processing. As for now I am going to keep both of them, later I'll see.

[jwcjrccc]

Thanks for your comments on your experience and thoughts on these lens.