louparker Loc: Scottsdale, AZ

My Pentax 18-250 zoom lens on my Pentax K-5 just "died" -- the creep lock froze up and then broke, and now the zoom ring and AF with that lens attached to the camera doesn't work (the lens just hunts continuously for focus). To zoom, you have to manually pull the barrel in and out and use manual focus. I know the problem with the AF is the lens because I attached it to a K-7 I still have and it does the same thing. I called the best camera repair shop in the area and they confirmed that the the lens and not the camera likely is the problem, but they told me that neither they nor Pentax supports repair service for that lens, and besides even if they did, it would cost more to repair than to replace it, and neither Pentax nor Tamron (who made the lens for Pentax) make that lens any longer.

So, I am looking to replace it with a new K-mount (or KAF-mount) zoom lens. As for new lenses, my options are: (1) Pentax brand 18-270; (2) Tamron 18-270; (3) Sigma 18-250; and (4) Sigma 18-300. The 1st 3 choices all use 62mm filters, but the filter size on # 4 is 72mm, which would mean that I have to also replace my $100+ 62mm circular polarizer. Price-wise, #3 is the least expensive, but #4 is only slightly more and has a longer range but would require buying a new polarizer, and of all 4 choices, it is slightly heavier. Your suggestions and recommendations?

krmitchell55 Loc: Springdale, Arkansas

Here's a discussion on Pentax forums.
www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/365806-pentax-18-270mm-vs-sigma-18-300mm-lens.html

FL Streetrodder

I use a Sigma 28-200 zoom on my Pentax along with a Pentax 55-300 lens and both perform well for me. The Sigma uses 72mm filters and is considerably heavier than the Pentax lens, but has a very useful zoom range for me. The Pentax 55-300mm complements my 18-55 lens nicely and uses 58mm filters.

assman Loc: Grand Rapids, MI

You might want to look at the Pentax 60-250. I think it is one of their best zoom lens made.

MT Shooter Loc: Montana

Read the review comments here for lots of first hand knowledge:
https://www.pentaxforums.com/userreviews/sigma-sigma-18-300mm-f35-63-dc-macro-hsm-c.html

Get one here:
https://www.uglyhedgehog.com/t-585177-1.html#10015661

PHRubin Loc: Nashville TN USA

I bought the Sigma 18-300 a while ago and am very happy with it. I do not have any filter on it, but ALWAYS have the lens hood mounted for protection. I keep it on my 80D and carry them around in a gym bag. I had it on my back seat when a deer crossed the road forcing me to jam on my brakes. The bag slid forward and fell to the floor. No damage to either camera or lens (or bag), though now I carry the bag on the floor.

Gallopingphotog

I have both the Pentax 18-270 and Sigma 18-300 (long, boring story....) and I much prefer the Pentax lens. Crisper

louparker Loc: Scottsdale, AZ

Thanks for your review -- can you tell me why you prefer the Pentax over the Sigma. I'm very conflicted having read good AND bad reviews for both lenses, so I would really appreciate your elaboration and experience with both.

Gallopingphotog

Sigma v Pentax: Right from the git-go the Sigma was sticky and stiff. The zoom ring (whatever you call the ring that makes the lens change distance) is just hard to turn. I thought it would ease up a little with use but it's still balky.
Like I said earlier, I think the image the Pentax yields is just a little crisper when compared side by side zoomed in in Lightroom.
The Sigma is a couple ounces lighter than the Pentax, but a good inch longer when collapsed.
And now just this week there's a problem with the contact points. Instead of showing the f/stop on the camera display, it just shows f/.... Doesn't matter if the mode is manual, AV, program, etc. I've tested the lens on both of my Pentax bodies, same result. With other lenses, the f/stop display is fine. Tried cleaning points with lens fluid but no luck. Guess I will be sending it to Sigma for repairs. No camera store anywhere near here unless you want to count Best Buy

louparker Loc: Scottsdale, AZ

Thanks for your comparisons. A couple of comments based on other reviews and specs I have read: (1) the stiff zoom ring on the Sigma seems to be universally noted by others; (2) all specs I have seen state that the Sigma is almost 5 ounces or 132 grams heavier than the Pentax (1.0 lb. vs. 1.29 lbs., 453 g. vs. 585 g.) because the Sigma lens is definitely physically larger overall than the Pentax lens; (3) curiously, most others who have compared the 2 lenses feel that the Sigma is sharper overall than the Pentax, so I definitely appreciate your opinion about that; and (4) I have seen no other comments about the display issues you described, but again, it's good to know about that -- have you tried cleaning the contact points with 91% alcohol or tuner cleaner instead of "lens fluid," which is not a very good cleaner for metal parts?

If anyone else can weigh in on a comparison of the 2 lenses, it would be greatly appreciated. Thanks again for your comments.

Gallopingphotog

have you tried cleaning the contact points with 91% alcohol or tuner cleaner instead of "lens fluid," which is not a very good cleaner for metal parts?

Thanks, I will try that. If that doesn't work, we are going to Las Vegas in May and there's a locally owned camera store I've done business with in the past. I'll take the lens, see what they can do. I am not inclined to spend a ton on it, since I prefer the Pentax lens anyway!

TreborLow

I went for the 18-300 and am reasonably happy with it. It has one annoying feature that lens extends by itself if pointed down. There is a lock for carrying it, but.... Sharpness is quite good upto about 250, and wide open is not as good as stopped down a stop or two. Thus at the longer end I find I am stopping down more than I would like. Nevertheless, it works very well as a general purpose lens. I went for a less expensive polarizer and for the few times I have used it, found it acceptable.
My 'better' lens is the Sigma 17-50, 2.8. Wonderful except for the reach. For that issue I was able to find a reasonably prices Pentax* 300 f4 prime and that is a truly amazing performer.
Good luck!
Bob