[twix23919]

I'm looking to purchase just one lens right now....I find that I use my 18-55 kit lens the most, but I'm not happy with the quality. Here's what I'm looking at:

• Pentax Zoom Super Wide-Telephoto SMCP-DA* 16-50mm f/2.8 ED AL (IF) SDM
• Sigma 17-50 f2.8 EX DC OS HSM

What is the difference between the two? What would make one better than the other? Does the Pentax one allow you to use the 2.8 throughout the zoom? I could not find that in the description on B&H.......thanks ahead of time for your input!

[bymy141]

I'm looking to purchase just one lens right now....I find that I use my 18-55 kit lens the most, but I'm not happy with the quality. Here's what I'm looking at:

• Pentax Zoom Super Wide-Telephoto SMCP-DA* 16-50mm f/2.8 ED AL (IF) SDM
• Sigma 17-50 f2.8 EX DC OS HSM

What is the difference between the two? What would make one better than the other? Does the Pentax one allow you to use the 2.8 throughout the zoom? I could not find that in the description on B&H.......thanks ahead of time for your input!

First, YES, they both let you have f2.8 troughout the zoom range.

The differences between the 2 are some times obvious, some times not:

1) Weather & dust sealed: Pentax Yes, Sigma No. When travelling the world (like we do) this is a very big plus for the Pentax.
2) AF motors: Pentax SDM, prone to failure, HSM not. Although my Pentax has lasted for 3 years and +100k shots by now...
3) Image Quality. The Sigma does better in tests at f2.8, the Pentax is soft in the corners at f2.8, one or more stops closed they are on par.
4) Size and weigth: Sigma is somewhat smaller, lighter.
5) Price: Sigma you should be able to get cheaper.
6) The Pentax is 1 mm wider, it sure makes a difference at the long end.

The latest Lightroom lens filters take care of all minor flaws like distortion, CA etc of the 16-50mm, I don't know if there are filters available for the Sigma yet.

I bought the Pentax 16-50mm 3 years ago and it has been my most used lens by far!
Sigma did not have the 17-50mm in its program then.

However, if I had to by a new standard lens today, I'd be having a very big dilemma: Sigma's IQ + HSM versus Pentax's dust & water sealing & 16mm....

Have a look here:

Pentax SMC DA* 16-50mm f/2.8 ED [IF] SDM - Review / Test Report
Sigma AF 17-50mm f/2.8 EX DC HSM OS - Review / Test Report

Cheers, Bert

[Cambo]

I'm looking to purchase just one lens right now....I find that I use my 18-55 kit lens the most, but I'm not happy with the quality. Here's what I'm looking at:

• Pentax Zoom Super Wide-Telephoto SMCP-DA* 16-50mm f/2.8 ED AL (IF) SDM
• Sigma 17-50 f2.8 EX DC OS HSM

What is the difference between the two? What would make one better than the other? Does the Pentax one allow you to use the 2.8 throughout the zoom? I could not find that in the description on B&H.......thanks ahead of time for your input!

still disgusted that THAT company actually put out a 300 F2.8 with the front element TAPED in place with double sided tape - absolutely appalling. Sure they've come up in quality since then (15-20 years ago), but would you trust a company with those kinds of ethics? I won't, ever.

They BOTh are 2.8 throughout the zoom range, hence only one aperture listed in their name, otherwise it would be 16-50 f=2.8-4.5, or something (look at the front of your kit lens). Also, optically, there are very few Sigmas up to par with the larger companies offerings, and even when the resolution is good, colour rendition and contrast often suffer, as does resale value. The Sigma owners will now scream and flame me, but the truth hurts sometimes...

My vote - stick with the Pentax.

Cheer,
Cameron

[jmschrei]

Have you looked at reviews? I do have the 16-50 and bought it as a kit lens with a rebate so the price was reasonable. It can produce some stunning images but has some significant weaknesses (purple fringing and weaker IQ at wide end bother me the most) and then there is the potential failure of the SDM motor. After 1.5 years I am starting to find I am unable to autofocus periodically, especially if I haven't used the lens for a while. And there is the other issue, the lens is huge and heavy and now that I have been building a collection of primes in that range I am less inclined to use it. I do like to own it, I do intend to have it serviced before my warranty runs out but I would be cautious to wholeheartedly recommend it. I know some people have opted for the Sigma and you should be able to access a wider range of user reviews and feedback for that lens outside of Pentax users for comparison.

Both lenses would be 2.8 throughout by the way, and remember the kit lens is a most basic lens, there are other options in this focal range that will be a step up in quality at a variety of price points.

-Joe

[elho_cid]

Image Quality. The Sigma does better in tests at f2.8, the Pentax is soft in the corners at f2.8, one or more stops closed they are on par.

On canon the Sigma was used on a smaller sensor. So the edge/corner performance is not directly comparable with the photozone tests you linked.
Also klaus doesn't do any MTF20 tests, only MTF50. This is typically the kind of test where Sigma sucks and Pentax excells.
But after all, the price difference is big...

[Pentaxor]

I'm looking to purchase just one lens right now....I find that I use my 18-55 kit lens the most, but I'm not happy with the quality. Here's what I'm looking at:

• Pentax Zoom Super Wide-Telephoto SMCP-DA* 16-50mm f/2.8 ED AL (IF) SDM
• Sigma 17-50 f2.8 EX DC OS HSM

What is the difference between the two? What would make one better than the other? Does the Pentax one allow you to use the 2.8 throughout the zoom? I could not find that in the description on B&H.......thanks ahead of time for your input!

I would go for the Sigma. the Sigma has come a long way of bringing out new and better lenses. the Pentax was a beast during it's time, but new lenses come along and the Pentax has some great competition now. besides, the only thing that is different with the Pentax is WR. IQ, reliability, durability, and Warranty, the Sigma would be of better value.

[Pentaxor]

On canon the Sigma was used on a smaller sensor. So the edge/corner performance is not directly comparable with the photozone tests you linked.
Also klaus doesn't do any MTF20 tests, only MTF50. This is typically the kind of test where Sigma sucks and Pentax excells.
But after all, the price difference is big...

how bout the DxOMarks tests?

[twix23919]

Hi everyone.....thanks for the input! lots of different views, one major dislike of sigma! I have read lots of reviews...hence being so torn.....this is a dilemma!

[Pentaxor]

Hi everyone.....thanks for the input! lots of different views, one major dislike of sigma! I have read lots of reviews...hence being so torn.....this is a dilemma!

well, you just have to read between the lines which are considered objective and subjective. I'm sure you'll find your answer.

[Pentaxor]

Also, optically, there are very few Sigmas up to par with the larger companies offerings, and even when the resolution is good, colour rendition and contrast often suffer, as does resale value.
Cheer,
Cameron

I'm not going to flame you because of your old experience which had led to your displeasing opinion regarding the Sigma's. but from an objective and present point of view, do you have anything that proves that all present Sigmas (including the new 17-50) don't have varying colour rendition and have weak contrast? and I don't care much about resale value since we are not selling irreplaceables or rare items and most lenses are sold cheaper than what they cost brand new.

I believe it is a great disservice to the OP if one's personal opinion spreads misinformation and bias.

[twix23919]

I am leaning towards the sigma....it seems from the reviews that I have read, most are very happy with this lens and it has a great warranty in comparison!

[dadipentak]

I have several Sigma lenses and I've been impressed by the quality. It's worth noting that, comparing warranties, it seems that Sigma has more confidence in, and takes more responsibility for, their products than Pentax does.

[DanWeso]

I am leaning towards the sigma....it seems from the reviews that I have read, most are very happy with this lens and it has a great warranty in comparison!

That would be my choice for those reasons.

[yongkun]

If you are using a K-5, you are better off with a DA* 16-50. I will pretty much go with the DA* 16-50, even though its performance at the wide end 16mm is not that good, but 1mm is still very important.

If you got a tighter budget then go for the sigma.

[twitch]

This model Sigma is one of those with a zoom ring that twists in the opposite direction to Pentax zooms. It doesn't seem to bother many people, but it drives me nuts with the Sigma zoom I have.

But then I went through 2 bad copies of a Pentax 16-50 before giving up. Because of shipping time and costs and the QC issues of the Pentax 16-50, it's a lens you should buy locally, or at least buy where you can have it shipped back and forth without crossing an international border. Oh yeah, make sure you factor in the cost of an extended warranty for the Pentax.