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07-29-2018, 11:59 PM   #1
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Looking for opinions on Sigma 17-50mm F2.8 EX DC HSM versus HD Pentax-DA 20-40mm ltd.

Hi all

I have been using DA 70mm prime on my K3ii for last two weeks. Like it very very much! This morning, I put back the kit 17-55 lens, go out shooting and seeing results later, I started searching for upgrade right away. The two lenses below are ones that come to my mind and would like to ask you guys for your opinions.

Sigma 17-50mm F2.8 EX DC HSM

HD Pentax-DA 20-40mm F2.8-4 Limited DC WR

I have read both lenses' reviews on Pentaxforums, seen phtos taken with them and just can't make up my mind.
As for now, it is lighter+WR 20-40 versus cheaper 17-50.
Also, as both lenses are made for aps-c sensors, I assume that the 17-50 & 20-40 are actual focal lengths.

Cheers!

07-30-2018, 12:45 AM - 3 Likes   #2
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Hello and welcome to the forums

I have both lenses, and they're quite different propositions.

The Sigma 17-50 f/2.8 has a constant aperture and larger focal length range, both of which make it the more versatile lens of the two in terms of field of view, subject-to-background separation and light gathering. It's sharp right across the frame, even wide open, but I find the rendering to be lacking a little in character. There's nothing wrong with it - it just doesn't have a lot of "soul", in my opinion (I've previously described it as "clinical"). But it's a great walk-around lens and capable of excellent results. I really like mine.

The HD DA20-40 is smaller and lighter, due to the variable aperture and narrower focal length range. It's weather-resistant, beautifully built, lovely to use, sharp at the wide end and renders very nicely. As you get towards the long end, the performance in the borders and corners is a bit disappointing - largely due to what I believe is strong field curvature, most noticeable at longer-distance focusing (another member here described it as "runway-style" field curvature, and I think that's quite fitting). In the past, I haven't been a big fan of the HD DA20-40, but I've been forcing myself to use it quite a bit recently, and I'm warming to it. Like any lens, you just need to get used to its quirks and use them to your advantage or work around them.

And yes... 17-50 and 20-40mm are actual focal lengths. Using these lenses with your K3II (with its 1.5x crop factor APS-C sensor), they're equivalent to 25.5-75 and 30-60mm on full frame respectively.

Last edited by BigMackCam; 07-30-2018 at 01:01 AM.
07-30-2018, 09:27 AM - 3 Likes   #3
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I have both lenses as well. the 20-40 has been one of my favorite lenses on my KS-2 and now KP bodies. I recently purchased the Sigma 17-50 and have been happy with it as well, but have not given it a thorough work out. The biggest advantages of the 20-40 are it's light weight, water resistant and has a pleasing rendering. My copy seems to be a bit better than average but it is still a lens that needs to be stopped down somewhat. That said I use it a lot and especially when I travel. I did switch out the lens cap, which I found fell off a lot, and and now use a step up ring to 62 mm, that replaces the tiny lens hood that comes with 20-40 and use 62 mm pinch cap. It does project out fairly far so the built in flash will cause shadows from the lens. Starbursts are no that great. But the HD lenses I have do not have the best starbursts (I use my green ring limited primes when I want great starbursts).

Regarding the Sigma, I tend to agree with Mike based upon my use of it so far. It is definitely less in weight than the Pentax 16-50 and seem to be pretty sharp though out it's range (much more consistent the an the 20-40). The starbursts on the Sigma are a bit better than on the 20-40 too.

The Pentax is lens I had to warm up to In the beginning i was not happy with it when shot wide open but there was something in how it rendered that persuaded me to keep it. Personally, while I like the 20-40 a bit more than the Sigma, I think that the deals right now on the Sigma are too good to pass it up.

Last edited by wstruth; 07-30-2018 at 09:33 AM.
07-30-2018, 08:56 PM   #4
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Thanks for welcome and your advice Mike & Bill!

QuoteOriginally posted by BigMackCam Quote
...the HD DA20-40 is smaller and lighter, due to the variable aperture and narrower focal length range. It's weather-resistant, beautifully built, lovely to use, sharp at the wide end and renders very nicely...

I think this is what I am after. Let's see what the deals are like around the web...
Cheers

07-30-2018, 09:45 PM   #5
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QuoteOriginally posted by oh_9000 Quote
I think this is what I am after. Let's see what the deals are like around the web...
Unless there's a pressing rush, I'd suggest waiting for a sale from Pentax Australia or dcxpert (an ebay outlet of C R Kennedy). They have sales periodically - typically 15% or 20% off. I got my DA 20-40 from dcxpert last year for $743 during a 20% sale.

Mike's summary of the 20-40 was on the money. I'd say mine is excellent at the wide end and very good at the long end; curiously its weakest point seems to be around 30-35mm, but even then it's still very good, particularly in the centre. Sample images here: Pentax DA 20-40mm Limited f2.8-4 - Flickr - Des(Australia)

But it's not necessarily for everyone. I got the 20-40 as a prime-substitute, not a substitute for a walkaround wide-normal zoom. I have wide coverage with a DA 12-24 (and a DA 18-135); I don't think I would have got the 20-40 otherwise. If it's sheer corner to corner sharpness you want (e.g. for architecture or classic landscapes), I suspect that the DA 16-85 might be better than the 20-40. (See the review by @NorthcoastGreg - Pentax DA 16-85 f3.5-5.6 | Reviews | The Northcoast Photographer) Like the 20-40, the 16-85 is a modern design, WR and has HD coatings. That lens also had a much more versatile range and is cheaper. The downsides are that it is bigger and heavier, and has a slower aperture. Which type of lens suits you will depend on your shooting preferences.

Last edited by Des; 07-30-2018 at 10:40 PM.
07-30-2018, 10:29 PM - 1 Like   #6
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Hey Des

Thanks for your opinion, appreciate it. I think, as you wrote, I'll stay patient for a bit as I missed on two pieces that were recently on sale on the forum...

QuoteOriginally posted by Des Quote
Unless there's a pressing rush, I'd suggest waiting for a sale from Pentax Australia or dcxpert (an ebay outlet of C R Kennedy). They have sales periodically - typically 15% or 20% off. I got my DA 20-40 from dcxpert last year for $743 during a 20% sale. ...

I have been outdooring (trekking, climbing) quite a lot - and I hope I will be! - and what I like about 20-40 is the size/weight versus performance ratio. All other lenses seem to be chunkier and heavier (200-500 grams). That is probably the main factor what tempts me the most.

Cheers Ondrej
07-30-2018, 10:45 PM - 1 Like   #7
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QuoteOriginally posted by oh_9000 Quote
I have been outdooring (trekking, climbing) quite a lot - and I hope I will be! - and what I like about 20-40 is the size/weight versus performance ratio. All other lenses seem to be chunkier and heavier (200-500 grams). That is probably the main factor what tempts me the most.Cheers Ondrej
That all makes perfect sense Ondrej. (I had assumed that weight and bulk were not big factors, because you were also considering the Sigma 17-50, which is a 500g+ lens.)

Down the track, if you find you want more width than the 20-40 offers, you could add the DA 15 Ltd, which is also rather compact and light weight, and which is also much loved for its DA Limited rendering.
08-01-2018, 09:55 PM - 2 Likes   #8
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Been shooting with my 20-40 as my primary lens recently in the Canadian Rockies... When attached to the KP admittedly with a battery grip it balances nicely on the camera and isnít a horse for size. FWIW it is my walk around lens on my KP, only has come off for the 15, 70-200 and 300 during the trip. This thing just works and has a incredible performance to size ratio plus is 2.8 at 20mm, which is nice.

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