[Salminus]

Hi everybody, first of all I'd like to thank everybody who has replied to my last Thread (about softness in k10d JPEGs). You helped me a lot and finally, I'm going for the k10d.

After some search I'm between two lenses
Tamron 18-250 3.6 and the Sigma 17-70 2.8.
I know the advantages and weaknesses of each one.

But how do you compare each other in terms on IQ
I guess (only guess) that the less extreme range and bigger aperture of the sigma should mean sharper images (I might be talking nonsense).
If so, do you think that this advantage the sigma might have in this aspect, justifies it’s shorter range?


I’d be doing mostly outdoors, lots of pictures in the Water (I’m a Fly fishing Guide) with a polarizing filter. Sigma rotates when focusing, but the polarizer would make the tamron even slower.
To make some of the kind of shots I want (freeze a fish jumping in the air) I’d need to shoot at 1/500. With a polarizer and in the sunlight do I need the 2.8 aperture?

It’s being really hard for me to make this choice range vs speed.

I hope you can help me to get out of this hole I’m into

Thanks

J

[matix]

Hi Salminus, you ask a complex question here. I have both lenses, and they are both my favourites. Both excellent in that their IQ is very good, and easy to use, but they are very different in applicaton because of their range.

I would say that they are equal in their ability to resolve crisp, clear images with great contrast throughout their ranges, but their ranges are the issue in my opinion.

Give the same conditions, good lighting, bad lighting, with polarisers and high shutter speeds, both at 70mm there would likely be little difference in their resulting images.

If the fish is less than 6 meters from you, both will be ok. If the distance is greater, the 17-70 will have a small image in a large frame, and the 18-250 will be able to compensate for the distance, while losing light of course.

Tough call, it really is dependent on position, lighting, distance and whether a smaller image in a large frame can be cropped to be as good as a larger image zoomed closer with the 18-250, which was harder to shoot at say 160mm than the Sigma did at 70mm.

NOTE: The Sigma 17-70 Objective lens DOES NOT ROTATE as you stated, no problems with polarizing filters at all.

Here are two images for comparison of the same subject, not a fish but you get the idea. The first is taken with the Sigma 17-70, the second with the Tamron 18-250. Taken at different times, so the lighting is somewhat changed.





And this one shot with the Tamron at 250mm as a nature comparison. I would never use the 17-70 for this purpose, unless the subject was a family pet and I could get in really close.



Hope this helps a bit

Phil

[daacon]

I agree with Matrix - I have the 18-250 and have been very happy with it. They are two very differnt lens used for different purposes. The 17-70 will do better in low light at f2.8.

I will also have to defer to Matrix with both on IQ quality - I can confirm I have had no complaints with the 18-250. I can say for a 'walk around' lens you would be hard pressed to beat the quality and range of the 18-250.

[Confused]

Hi Salminus

I too have the Tamron 18-250mm Di II zoom lens and am utterly delighted by it's excellent image quality, solid feel and compactness. However, if you're going to be using a polarizing filter on the Sigma, it's rotating front element could virtually drive you nuts with frustration when trying to compose images....just a thought ? I haven't tried the Sigma, so it would be unfair of me to comment on it's qualities.....

Best regards
Richard

[WMBP]

Nice bird pic, Phil!

J (Salminus), you're asking a question that nobody can answer but you. It's like asking, should I buy a pickup truck or a sports car? The only answer is, which one do you want more?

I don't have the Sigma 17-70 f/2.8 but I've read excellent things about it. One of the problems with the Tamron 28-75 f/2.8 that I have is that it sometimes just isn't wide enough; and the Pentax 16-45 f/4, which I also have, sometimes isn't long enough. If I were buying lenses now, I think I might prefer to have that Sigma instead of BOTH of those other lenses. For my purposes the difference between 16 (Pentax) and 17 (Sigma) is negligible. But able to go to f/2.8 at 17-20mm is definitely NOT negligible. I'm not sure the Sigma's image quality is quite the equal of the Pentax 16-45, but I'm not a perfectionist in those matters; it seems close enough.

The best answer to your question is obvious: get 'em both. But if that's not possible right now, then the only answer is, which one do you want more urgently?

If you insist on getting an answer to an unanswerable question, I'll give you one, or at least I'll tell you how I answered a similar question for myself and why. When I faced a similar choice, I went for the more versatile lens first. I think that's reasonable. I mean, if your budget completely dries up tomorrow, the 18-250 would be more generally useful. The main difference is that one stop (or less) difference in the range that they have in common (18-70). Worth something, but not the end of the world.

But I know others who've done exactly the opposite: concentrate on getting good lenses for specific purposes, without worrying about versatility. I can respect that, too. Depends on what you like to shoot!

Best I can do. ;-)

Will

[matix]

Thanks Will...

[Salminus]

Thanks everybodyfor your replies.

Will, I know this is something I would finaly have to decide by my self.
I just wanted you all, who are far more experienced than me, to tell why would choose one or the other lens, so that can help me to make up my mind.

I'm aware it's something personal, and a metter of taste, the thing is that I'm not experienced enough to tell what I would like more(if you know what I mean)
Thanks for the patience anyway.

And Phil, Thanks foryour post was great and very helpfull, Thanks a lot

I guess I'd be missing more the extra range than the speed so far...

Joaquin

[pcarfan]

I was going through the same process a few weeks ago, I settled on the 18-250 first and then the K10D.

Some images I posted at dpreview:


Cincinnati Zoo: K10D Tamron 18-250. (11 img no 56k): Pentax SLR Talk Forum: Digital Photography Review



Like it says there, I'm new to this.....

[frank]

Hi Salminus

I too have the Tamron 18-250mm Di II zoom lens and am utterly delighted by it's excellent image quality, solid feel and compactness. However, if you're going to be using a polarizing filter on the Sigma, it's rotating front element could virtually drive you nuts with frustration when trying to compose images....just a thought ? I haven't tried the Sigma, so it would be unfair of me to comment on it's qualities.....

Best regards
Richard

Sorry Richard, the Sigma 1770 doesn't have a rotating front element, and it is perfectly fine when using a CPL filter - as addressed by matrix above.

[Confused]

Hi Frank

That's fine because as previously stated, I've never actually seen a Sigma 17-70mm in the flesh before and thought it appropriate not to pass judgement on the lens, as I was naturally commenting purely on the information supplied !

Best regards
Richard

[bymy141]

Here are a few more samples made with the K10D / Tamrom 18-250mm combination. As you can see, the Tamron lens is not extremly sharp and there is vignetting at the low end of the lens. The last issue can simply be correct in PP. These pictures were taken raw, PP in Bibble Pro, than shrunk for posting purposes. If you like some of the original files for detailed examination, let me know.

- Good luck, Bert

[rfortson]

I have the 18-250, and while I really like it, the CPX filter may be a problem for you if you use the hood (really recommended). There's no notch in the hood, so adjusting the polarizer is a real pain, and you'll probably wind up with fingerprints on the filter. I bought a polarizer for my lens, but gave up trying to use it for just that reason. I just keep a UV/haze filter on there now, along with the hood.

If you ditch the hood, the polarizer should work fine, but then you have a potential for flare. Pick your poison, I guess.

[Jacob]

However, if you're going to be using a polarizing filter on the Sigma, it's rotating front element could virtually drive you nuts with frustration when trying to compose images....just a thought ? I haven't tried the Sigma, so it would be unfair of me to comment on it's qualities.....

The Sigma 17-70 does NOT rotate.
I do not know where you have the information from.

[WMBP]

In my post earlier, I compared the Sigma 17-70 to my Pentax 16-45 (at the wide end) and my Tamron 28-75 (at the long end) and as I was writing, I began to think about replacing both of those lenses with the Sigma.

But I just looked: The reason I haven't done this already is that the Sigma isn't a fixed aperture. The 17-70 is f/2.8 (at 17mm) and 4.5 (at 70mm). (There's a new HSM version of this lens but it's got the same aperture range.) So it's fast only at the wide end, and the lack of a fixed aperture is a problem for me shooting in this range.

The Sigma 17-70 f/2.8-4.5 looks like a killer replacement for the Pentax kit lens: it's a bit longer, a bit faster, and probably has a bit better image quality than the kit lens. But this thread was titled in a way that suggests you're trying to decide between telephoto reach and speed. So I want to point out that the Sigma is not really what I would call a "fast" lens. For me (but I think for lots of other photographers), fast means that I can use the lens to shoot an indoor event where the light's not good and I can't use flash; and that means f/2.8 or wider, throughout its range -- not f/2.8 at the wide end only. My point isn't to quibble about the definition of "fast," but simply to point out that this lens's specs aren't quite as exciting or distinctive as I thought at first. If you shot outside a lot, or with flash, it might be tremendous. As I said, great replacement for the kit lens. And not too expensive: available from B&H, Adorama or Amazon for well under $400.

But if you've got the kit lens already, then I'd think going for the Tamron 18-250 would complement it much more powerfully than buying this Sigma.

[JeanneB]

I'm trying to make the same difficult decision as the OP. Sell my 18-55 and get the 17-70 to use in combination with my 50-200 or get rid of my 50-200 as well and get the 18-250 so I have a single walkaround lens (I was originally looking at the Sigma 18-125 in hopes of reducing the amount of lens changing I do on vacations). I've been thinking about it and reading through threads like this on all the photography boards for a week and I still haven't made up my mind. The only thing I've accomplished is narrowing my original list from five lenses down to two, at least I'm making progress!!

I'd love to get both but I just bought the 10-17 fisheye so that kind of blew my budget.