Which 17-70mm lens?

I'm looking for a 17-70mm. Sigma, Tamron & Pentax appear to be the choices. I have looked a Photozone and they seem to like all of them so I would appreciate anyones opinion to help me make a decision. I want as much speed as I can get but I think the 2.8-4.5 loose the 2.8 pretty quick but they are only 1/2 stop slower than the Pentax at the long end. The most important characteristic to me is sharpness.
Your help would be appreciated.
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You pay for what you get but you don't necessarily get what you pay for

I didn't know that Tamron had a 17-70 (and still don't think so - are you referring to the 28-75?), but I do know that the Sigma enjoys a very good reputation (and so does the Tamron 28-75, in fact).

Faced with the same decision as you, I went for the Pentax despite the higher price and I am very happy with it. It is solid, relatively silent and sharp enough for all real-life situations. It is not weather sealed itself, as you probably know, but it has a rubber seal that appears to ensure that the camera itself remains weather sealed with the lens on. In fact, this gave me some peace of mind all day today when I was out shooting in a drizzle.

Although I was quite impressed with samples from the Sigma I went for the Pentax on account of the solid build (I found several complaints about the build of the Sigma), constant focus (I have a thing against variable focus) and colour rendering, which I find to be excellent.

I know this is probably not very helpful, but at least it will keep the thread alive for some additional minutes.
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Shooting since '59 and still waiting for a keeper

You are right. I was mistakenly looking at the Tamron 17-50mm. I guess I'm getting tired (and old). Thanks for your reply. It looks like the Pentax is over $100 higher so I guess you feel like it was worth it?
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You pay for what you get but you don't necessarily get what you pay for

rondeann wrote:
It looks

rondeann said:

like the Pentax is over $100 higher so I guess you feel like it was
worth it?

Click to expand...

I did indeed. Since it was the 17-50 you were talking about (and not the 28-75, as I mistakenly assumed) I will add that the reason I chose the Pentax over that was not build quality or colour rendering (although I prefer Pentax), but simply the extra reach, which was important to me. In my view a price difference of USD 100 is not significant when you are talking about a "lifetime" investment (whatever that means these days).

As it happens, the 17-70 is the only lens that I have "tested" after buying, because a software/monitor problem had me mistakenly worried that the lens was soft. These images are not big enough to judge the lens sharpness, but I include them because they do illustrate what I mean by colour rendering and they do show what you can expect straight out of the camera from raw (images are unprocessed).

Warning: Boring images.

Taken at 43 mm (to compare with my FA43) at 5.6, where the lens really starts coming into its own:



Brick wall at 4.0 (where this lens is supposedly "softish") and 63 mm (note that the brick wall is curved (s-shaped) so it is not a proper "brick wall" test (I have that too, if your are interested):



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Shooting since '59 and still waiting for a keeper

Just to add, there is new incentive to buy Pentax glass with the K-7. If you shoot in JPG mode (or process RAWs later in Pentax Photo Lab) you can automatically correct distortion and CA in the Pentax lenses. This won't work with the off brand lenses.

I have the Sigma 17-70mm and really like it. I love the macro ability with it and it is fairly sharp, especially when stepped down to f/5.6 or so. I bought it cheap used (about $200 US) so that is the only reason I bought it. If you want the macro ability, but if I were just buying a general purpose standard zoom I would go with the Pentax. The Sigma is effectively a 1:2 macro or so (maybe it is 1:2.3 or something), that is very wide angle. Great for interesting perspective macro shots, but I wonder if it trades some sharpness at infinity for close focus ability? I haven't used it for enough landscape shots to know.

The build on the Sigma is fine, but it is very susceptible to zoom creep, if I have it set for 17mm and point it down it immediately extends to 70mm. Overall it feels like any Sigma EX lens, even though I don't think it is an EX lens.

Eric
--

I never saw an ugly thing in my life: for let the form of an object be what it may - light, shade, and perspective will always make it beautiful. - John Constable

See my Blog at: http://viking79.blogspot.com/
See my Flickr Photostream: http://www.flickr.com/photos/28177041@N03/
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad

I have Sigma 17-70 and it is a great lens. My copy is sharp at any aperture and any focal length. The 50mm on Tamron is really 45mm which is too short for portraits and for my use. Sigma is sharper at 70mm compared to Pentax (Photozone) which is important for me.
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'Forget about what you don't have, and focus on what you have' it is the best advice I got from this forum

basic state of ignorance said:

I have Sigma 17-70 and it is a great lens. My copy is sharp at any
aperture and any focal length.

Click to expand...

I am not saying mine Sigma isn't sharp wide open to f/5.6, it is just no sharper than the kit lens in that range, which is also reasonably sharp and this experience matches with Photozone's review. The kit lens is a good all around lens, but the Sigma 17-70mm excels at f/5.6-f/8 and at macro, and the larger aperture can come in handy and the extra reach is really handy as you mention. However, if you don't shoot with the Sigma at f/5.6 to f/8 on occasion (at the wider end) you are missing a special treat.

Middle Path said:

The 50mm on Tamron is really 45mm
which is too short for portraits and for my use. Sigma is sharper at
70mm compared to Pentax (Photozone) which is important for me.

Click to expand...

These zooms always give up focal length at close focus, I imagine the Sigma does it too, but if you need 60mm up close the Tamron is going to fall far short. The Tamron/Pentax 18-250mm is only like 150mm at close focus. It has to do with how they focus. Primes will give up a tiny bit, but not nearly as much. Focal length is always rated at infinity. At macro focus I think the Sigma at 70mm looks more like a 35mm, but it focuses basically on the lens front element.

Again, all these lenses are good, get one that works best for your needs. If I wanted more uniform (corner to corner) performance at 17-35mm I would buy the Pentax. If I wanted a little faster aperture (1 stop at the wide end) I would look at the Sigma. If I was mostly concerned with performance at the tele end, I would definitely lean towards the Sigma, although the Pentax isn't bad there. If I wanted minimal CA I would lean towards the Sigma, although the K-7 might help the Pentax in this regard. Macro ability? Sigma. Landscape lens? Pentax.

Eric

--

I never saw an ugly thing in my life: for let the form of an object be what it may - light, shade, and perspective will always make it beautiful. - John Constable

See my Blog at: http://viking79.blogspot.com/
See my Flickr Photostream: http://www.flickr.com/photos/28177041@N03/
See my PPG Shots: http://www.pentaxphotogallery.com/erictastad

I have the Pentax 17-70mm. lens, I love it, since I got this lens I have given my Pentax 16-45 and Sigma 17-70 to my adult children. In my experiece this is the best zoom lens I have. I also enjoy the close focus thru the full range from 17 to 70. I enjoy the speed of focus compared to the 16-45 or the Sigma 17-70.

First one was de-centered..... Returned it to B&H for an exchange and the second one was excellent!

My only thoughts are that: (1) given all the other sealed lenses Pentax is making (new low cost sealed lenses) - would have really been NICE - especially given the great variety of sealed bodies Pentax offers. - and - (2) I wish they have made it a 17-105 or 135. Personal desire as I find I shoot more at that range than the wide end.

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Bob

rondean,

I haven't tried the Pentax, but I have had the Sigma for about 2 months....ish.... I have been really impressed, the CA is well controlled, the Macro ability is really nice, the range is a nice range for a landscapey/walkaround lens. I was a little leery of the Pentax because I am not sure of the implementation of the SDM yet.

I don't think you would go wrong with the Sigma at all.

Lloyd
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If it doesn't matter whether we win or lose, why do we keep score? --Worf Son of Mogh

http://lloydshell.blogspot.com/
http://main.diabetes.org/goto/Lloyd.Shell

I had both DA17-70 and Sigma 17-70, neither were great examples (unusually soft at the long end for both). It was much easier to swap out the Sigma (local compare to overseas for the Pentax) so I got a new Sigma. It's better than the first but I find it an unimpressive compared to my DA*16-50 and even the FA24-90 as at least as good.

The Pentax on the other hand was a much nicer lens all around. Sealed at the mount so at least provides some body protection compared to any except the DA* lenses. Nicer handling than the Sigma but thicker in the barrel. Good examples of the DA17-70 are excellent optically - Photozone has better numbers for it than the Sigma and with the nicer handling and "Pentax' look to the colour rendering I'd pay the extra for it again.

My Sigma will go on eBay, not because it's a bad lens, it just doesn't stand out in any way and every other Pentax lens I have covering the focal range does a better job than the Sigma.

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Brett
http://www.pbase.com/shreder



The Journey is the Thing

Now for the hard part. Decisions Decisions
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You pay for what you get but you don't necessarily get what you pay for

Its simply a nicer lens and has more reliable exposure and colour, is sharper at the wide end and only slightly softer in the corners at 70mm.

I use it for everything and its pretty sharp - I did have to try 3 of them, but same was true for the Sigma which I now sold.

The Sigma is a fine lens - I sold mine to Luzart - but not quite as good or as quick to AF in low light.

rondeann said:

Now for the hard part. Decisions Decisions
--
You pay for what you get but you don't necessarily get what you pay for

Click to expand...

--
Steve

Any fool can take a picture OF something. Its much harder to take a picture ABOUT something.

I don´t have the Pentax version, but am VERY happy with my Sigma 17-70
Low light action is very good IMHO

Examples of its sharpness





RemcoR

I am interested in your testing procedures. I went through three Tamron 28-75/2.8's and never got what I would call a good one. I finally decided to keep the last one and send it to Tamron and see how it came back. So far I haven't sent it in. It just sits on the shelf. That is why I'm now looking at the 17-70mm lens in addition to wanting something wider than 28mm and with some speed. The Pentax has a constant f4 which is not very fast and the Sigma starts off at f2.8 but I'm sure it looses that very quickly but at it's long end is only 1/2 stop slower than the Pentax.

For me testing a new lens always seems to come down to a subjective decision unless it's got an obvious flaw. Do you use a step by step procedure and if so what is it?
--
You pay for what you get but you don't necessarily get what you pay for

rondeann said:

The Pentax has a constant f4 which is not very fast and the Sigma starts
off at f2.8 but I'm sure it looses that very quickly but at it's long
end is only 1/2 stop slower than the Pentax.

Click to expand...

Sigma f-stops....

17-20mm f/2.8
21-24mm f/3.2
24-34mm f/3.5
35-54mm f/4.0
55-70mm f/4.5

--
You pay for what you get but you don't necessarily get what you pay for

Just a little correction:
The sigma is f/2.8 up to 21mm (not 20).

Brad99 said:

rondeann said:

The Pentax has a constant f4 which is not very fast and the Sigma starts
off at f2.8 but I'm sure it looses that very quickly but at it's long
end is only 1/2 stop slower than the Pentax.

Click to expand...

Sigma f-stops....

17-20mm f/2.8
21-24mm f/3.2
24-34mm f/3.5
35-54mm f/4.0
55-70mm f/4.5

Click to expand...

--
Florent

http://www.pentaxphotogallery.com/florentgl ück
http://www.flickr.com/photos/thxbb12/

Sigma stays f4 until 63mm. The rest of the numbers is wrong as well

thxbb12 said:

Brad99 said:

rondeann said:

The Pentax has a constant f4 which is not very fast and the Sigma starts
off at f2.8 but I'm sure it looses that very quickly but at it's long
end is only 1/2 stop slower than the Pentax.

Click to expand...

Sigma f-stops....

17-20mm f/2.8
21-24mm f/3.2
24-34mm f/3.5
35-54mm f/4.0
55-70mm f/4.5

Click to expand...

--
Florent

http://www.pentaxphotogallery.com/florentgl ück
http://www.flickr.com/photos/thxbb12/

Click to expand...

--

'Forget about what you don't have, and focus on what you have' it is the best advice I got from this forum

Brad99 said:

rondeann said:

The Pentax has a constant f4 which is not very fast and the Sigma starts
off at f2.8 but I'm sure it looses that very quickly but at it's long
end is only 1/2 stop slower than the Pentax.

Click to expand...

Sigma f-stops....

17-20mm f/2.8
21-24mm f/3.2
24-34mm f/3.5
35-54mm f/4.0
55-70mm f/4.5

Click to expand...

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But the Pentax bokeh is very smooth. Aperture is not always that important.

And at F2,8 and 17mm the Sigma is not sharp.

Steve

Any fool can take a picture OF something. Its much harder to take a picture ABOUT something.