[Funsize]

I used to really like the Pentax 18-135 but a few things happened that made me leave it off my camera. The first was the sigma 18-35, and the second was upgrading from a 15" screen to a 27". I had a lot of landscapes I took with Pentax that were just slightly off, and I couldn't figure out what was wrong with them. They sorta hurt to look at, and no matter what I did, they just didn't look right. When I got the larger screen, suddenly I could see what was wrong. Not only was there no fine detail in the corners, but they were downright smudgy. The center would be fine, but everything else looked like a mess. Looking back, I could have upped the aperture to f/8, but a lot of my shots were impromptu, often at dusk, and I would have had too much motion blur. The sigma is orders of magnitude sharper (assuming you can get it to focus, which it does quite well past 2.8). Previewing shots on the back of the camera became surreal; since I was so used to the soft edges, I was shocked by how much more I could see with the sigma lens as I went around the image checking my shot. It was sorta like getting properly fitted glasses for the first time, you didn't know what you were missing.

Long story short, the Pentax 18-135 is ok for landscapes on smaller screens at higher apertures, but the Sigma 18-35 is going to give you much better results which will stand up to enlargement.

[normhead]

I've always had a 27 inch screen, so, that's not an issue with me at all. My advice would be, your lens needs calibration.





Right off the edge, pixel peeper, razor sharp, I included the icicle just to show how sharp it is. Taken at 48mm. While you can't really prove a negative... it's easy to disprove and argument like the above. All that says to me is, you don't have a good copy. That's a 1:1 crop, and it doesn't matter how large you print that image, thanks to modern enlargement algorithms it's going to look sharp, at practically any size.

The disadvantage of the 18-135 is lack of lack of a wide aperture.. The disadvantages of the 18-35 are lack of range and weight.

You can get a bad copy of either, and the 18-35 seems to have a disproportionate number of copies with focusing issues. If you want to start piling on either lens for "weaknesses declares near fatal on the internet, that's pretty much a waste of time. You buy a lens for what it does. But if your lens doesn't so what you think it should, it doesn't mean every lens like it is the same.

And if you get a bad copy of either should you decide on one or the other, send it back. Neither have a 100% keeper rate, but overall Pentax has a better keeper rate than Sigma, although I have no data on these two lenses in particular.

This print, printed at the above print quality for the 1:1 but but higher res at say 120 dpi (expanded to 300 dpi) would be 40 inches wide. And it would look good at that size.

[MadMathMind]

What are you trying to do? The lens you picked couldn't be more different. The 18-135 is a general purpose and versatile lens that will you give you quality photos of ordinary events and people. Do you want shots like these?



or with the 70-200...




Because the 18-135 isn't going to do that for you--you can't restrict the DoF enough with it. But if you just plan to shoot at f/5.6 or so and above, then the 18-135 will do a very nice job for you!

---------- Post added 04-10-15 at 10:45 AM ----------

Previewing shots on the back of the camera became surreal [with Sigma 18-35]

Amen to that! Shots on the back screen look so good that you really can't see the flaws until you get home. In that respect, it's a bit of a curse.

[Funsize]

I don't think my 18-135 was a bad copy. Like I said, I used to really like it; the center was quite sharp and was pretty much always in focus. The problem was pretty much everything that wasn't in the center. This can be used to your advantage, though, because it will help with subject isolation if you're taking a picture of an individual thing. I've got lots of portraits with it that are really nice, but I'm going to need to reshoot every landscape I took with it.

[normhead]

I don't think my 18-135 was a bad copy. Like I said, I used to really like it; the center was quite sharp and was pretty much always in focus. The problem was pretty much everything that wasn't in the center. This can be used to your advantage, though, because it will help with subject isolation if you're taking a picture of an individual thing. I've got lots of portraits with it that are really nice, but I'm going to need to reshoot every landscape I took with it.

Thats why I gave you an example of an edge image with great edge sharpness. It's a different lens between 20 an 50 mm, than it is between 70-135. That needs to be acknowledged when discussing edge weakness. At 24 mm, it's pretty much the same as the best out there, although I haven't seen results from the 18-35. And as I've pointed out, there are many ways to achieve subject isolation... there is one it's not so good at.... the one that requires wide aperture. But at subject isolation it does just fine in many circumstances...

You don't have to completely obliterate the background to achieve subject isolation.




The 18-35 is a better lens for some things... and it has advantages. I agree. But the 18-135 also has some things going for it to, this is not a slam dunk. The 18-35 is not going to be the best lens every time, unless you have a lot of other lenses to go with it, and you're OK carrying all that weight. In fact, if you don't have a lot to go with it, for most shooters, it's a very limited lens. For the guy who has everything, it's certainly a nice addition to the camera bag.

For most outings I have trouble justifying the weight of my Sigma 8-16, and it covers a focal length not covered by any other lens, so has a unique spot in the lens line up. A lens like the 18-35 overlaps with a lot of different lenses, from the 20-40 to the kit lenses, the 16-50/17-50 etc. It's pretty much only of value to those who feel they have to have the 1.8, in which case, there simply are no other Pentax options.

As soon as he said "Carry in a back pack, with room for one other lens", I ruled it out. Too limited range. Really heavy. Just not that kind of lens.

I'm providing images here, that show exactly what I'm talking about. I'm not sure how there could be a misunderstanding.

[Fauxton]

I have a question if you were going to take your k3 out to take photos of what ever came up from in town shots to landscapes to animals , and you have a small backpack camera holder with enough room to hold 2 good size lens one on the camera like a sigma 2.8 70-200 and a sigma1.8 18-35 . that fits next to the 70-200. would you take a pentax 18-135 or the 2 sigma lens . I don't know anything about the pentax 18-135 and I was wondering if I would be able to get as nice and sharp photos from the pentax lens as I can with the sigma lens . I don't care about the extra weight . I was thinking about getting the pentax lens if you people thought it would compare in sharpness to the sigma lens . I also don't mind changing lens . I'm also not going to go out on a rainy day so the water seals won't matter to me .

If you don't have the Sigma 18-35 and have a good copy I'd recommend against it. Check the reviews here. The lack of predictable focusing would be very problematic. The Sigma f2.8 70-200 is a fine lens. If you have that lens then the 18-135 Pentax doesn't match it well. I would recommend something that keeps you in the f2.8 area and performs well and reliably. Choices there would be the Sigma 17-50, Tamron 17-50 or if you have money to burn the Pentax 16-50. You may also want to consider the Sigma f2.8-4 17-70. Those would be my recommendations given your parameters.
If you just have those three lenses (Sigma 70-200, Pentax 18-135, Sigma 18-35) I'd go with the Sigma 70-200 and the Pentax 18-135. This would be on the known predictability of focus of the 18-135 over the Sigma 18-35. Its better to be in focus and soft near the edges than misfocus and be soft all over. I have the 18-135 and its a good reliable performer. Not as sharp as my 17-50 but quite good across the range.

[pentaxk3user]

Thanks everyone for taking the time to give me your thoughts. I really like this forum .I'm a amateur and I try to take in as much info about thing that I can .And I'm really surprised that you all take the time to help us out . I guess what I was thinking was if the 18-135 was a really good lens like I see from the photos posted for around 250.00 it would be a nice lens to get and keep on the camera .I'm not a pixel peeper or anything like that , I mainly just want what in the center to be in focus like a persons face or a building or a car things like that . I think I was asking if the sharpness was close to the 18-35 and the 70-200 and if it was close enough I could just use it and use the other lens for more specific things . I do have a 1.8 50mm that came with the k3 that is easy to keep with me . I guess I'll just get it and give it a try .If nothing else I can use it for photos or videos from my tree stand when I'm hunting on the rainy days . From all the photos I have seen It just looks like a good lens to have . Thanks again for your help .

[HAHA]

I have all three of the lenses and I would say that they can't really be compared. The Pentax 18-135 is a versatile and compact lens if you are on the move. The Sigma lenses are superior optically and are always the choice if you can afford the weight. The 70-200 is about the only option for action photografy with Pentax up until now. The 18-135 is pretty quick but not compared to the Sigma 70-200.
At the wide end, you have many more options than the 18-35. The Sigma is sharp but very heavy so you might be happier with some 17-50 F2.8. Both Tamron and Sigma have those. I have the Tamron and it stays on the camera a lot even though I have the other lenses.


But every now and then, It's starts raining, snowing or whatever... Then the Pentax is needed.
I guess you need a lot of lenses.....

[formercanuck]

Personally, I think it really depends on what you're shooting, and what you're looking for.
You mentioned that
a) you don't mind changing lenses
b) you're not going to be in rain/places where weather sealing is an issue.

I know that I have and really like making use of my 50mm f/1.4 and 28mm f/2.8, but for 'general outdoors' for me, I always use my 18-135mm WR.
a) Its convenient (i.e. I'm not going to miss a shot changing lenses)
b) lighting, I don't have to worry about light much (SoCal is always sunny)
c) it is a decent lens
d) outdoors - I use it mainly outdoors wherever I go. My old Sigma 18-200mm DC lens fogged up badly in Alaska drizzle

That being said, if I had to carry a couple of zooms, i'd be looking at a Tamron 17-50mm f/2.8 and 70-200mm f/2.8 as a pair. I

[normhead]

In Pentax APS-c land the DA*60-250 is the lens to go with your Tamron 17-50, unless you desperately need ƒ2.8. That one stop can mean a lot to some people. If you aren't one of those people a 70-200 is quite heavy for less range and sharpness. And I really wish people who claim something would make a big difference would post two photos not one. One at the next ƒ stop. I've surprise myself so many times doing this type of comparison, I take others who make these pronouncements very lightly. I would say, based on my experience, if you shoot every aperture from wide open to ƒ16, it's very rare the wide open image is the best, like maybe one in 10, Most of the time the subject in focus/ pleasing OOF areas factor, does not favour a wide open aperture, even on a 2.8 lens.

[formercanuck]

I tend to agree... especially outdoor/daylight. I've found that f/2.8 on some lenses is actually too bright at even 1/6000.

I'll be up in your neighborhood in July, Norm. Staying a week upstream of Ottawa on the river.

[normhead]

Cool, Ottawa up river is probably 3 hours from here....but if you get a chance, stop by. Mind you we get busy in July, we've already a 12 day trip booked end of July, so pretty good chance we'll both be gone.

[formercanuck]

Well... its ~45km outside of Ottawa near Dunrobin. Family is coming down south from Elliot Lake area to meet up.