Hello mire. I found one of these Sun 28-80's for sale cheap on a local web site. Just wondering how things worked out with yours?

Sorry for the novel, but here goes :

Stefan, in my admittedly (very) limited experience, I have found the Sigma to be sharp across the board. Also, in my limited, and unscientific testing the Sigma gave me the best overall results of the 3 lenses I looked at. Price wise, it was in the middle of the price range of the 3.

Our local camera shop has a 21 day return policy - buy a lens and use it for up to 21 days. If you don't like it they will take it back and give you a full refund - assuming it is in original condition, with all the packaging etc. If that is an option it may be the best way to be sure you are getting what you want/expect.

There are a lot of folks here with a lot more knowledge and experience than I have (or will probably ever have) so listen to what they have to say. These are only my observations, and potentially flawed opinions.

Personally, I have a strong aversion to chromatic aberration. The Tamron was the least expensive, but had the most CA (a lot in my opinion). The Pentax displayed less CA than the Tamron (probably livable, though still troubling to me). It was more than double the cost of the Tamron, and ~30% more than the Sigma. The Sigma had the least amount of CA - hard to see even after cropping, and was at least equally sharp to my eyes. And regardless of the price, I am more than happy with the results it has given me.

Here are some samples - all are shot at max zoom (300mm). I'm not sure what percentage the crops would be considered, but they are all cropped deep into the originals.

Pentax smc DA 55-300 @ 300mm
link

Pentax smc DA 55-300 @ 300mm - Crop - some CA visible
link

Tamron AF 70-300MM @ 300mm
link

Tamron AF 70-300MM @ 300mm - Crop - lots of CA Visible
http://picasaweb.google.com/RobStr86/TestShots#5431573227082738738

Sigma 70-300 @ 300mm
http://picasaweb.google.com/RobStr86/TestShots#5431571515928976546

Sigma 70-300 @300mm - Crop - very slight CA visible - see extreme left side of full version
http://picasaweb.google.com/RobStr86/TestShots#5431574086382583394

Sigma 70-300 @300mm - Crop - very slight CA visible - see middle left side of full version
http://picasaweb.google.com/RobStr86/TestShots#5431569446211841474

Unfortunately I was not able to test the Sigma in the same location, and under the same conditions as the Pentax and the Tamron. But I think the Sigma shots are still high contrast, on a bright day, which should exaggerate/cause CA to appear if the lens is going to produce it.

Ultimately I am very happy with my decision, and for me that's the bottom line. Do your research, test if you can, and choose the lens works best for you.

JD

Now I preface this by saying that I am a newbie, and the information below is purely anecdotal. There was not a lot of science in my tests, just my observations.

I recently bought the SIGMA 70-300MM F4-5.6 SIGMA APO DG MACRO to go with my K-x and kit lens. IMHO this lens has amazing IQ, with little or no CA (even enlarged to over 100%), and very sharp focus. On the down side the AF can be a bit noisy, and the lens does turn when focusing, so using a polarizing filter is a pain. For me it represented the best value, but the overall image quality and especially the lack of CA swayed my decision.

Before buying the Sigma I also tested the Pentax smc DA 55-300mm F4-5.8ED, and the Tamron AF 70-300MM F/4-5.6 Di LD Macro 1:2.

While the Pentax was good, I did not find it was quite as sharp as the Sigma or the Tamron, and it displayed some CA - not a lot, but noticeably more than the Sigma, thought significantly less than the Tamron. It was also significantly more money than either.

The Tamron was probably as sharp as the Sigma, for a lot less money (less than 1/2 the price of the Pentax), but it displayed the most CA of the 3 - in my opinion there was a lot of CA (apologies to Tamron users ).

I tested all 3 lenses on the same bright, sunny day, at about the same time of day, so they all had equal opportunity to display their strengths and faults.

Welcome Phil. Like you, I joined the forum before acquiring my K-x. After much research, and listening to lots of advice, I got it in late December. I think you've made a good decision going with Pentax, and joining this forum .

I have to agree with Wolf and Geoff. I've had my K-x for a few weeks now, and am constantly amazed. It's my first DSLR, and I did a lot of research (and agonizing ) before I made the purchase. Low light performance was important to me as I had been disappointed with that aspect of my previous camera - a Canon S5 IS. I realize you can't compare a point and shoot with a DSLR, but low light performance was high on my priority list. A site that finally helped me make up my mind was this one: http://www.imaging-resource.com/IMCOMP/COMPS01.HTM. I used the Comparator to compare a lot of cameras to the K-x, and was quite amazed by this little baby . Hope this may help others who are in the throws of making a similar decision.

Welcome Gunner. Sounds like you are off to a great start, and continuing in your granddads footsteps - as a Pentaxian

Welcome Russell

Welcome aboard Duncan

Hello and welcome from a fellow Canuk . Great moon shot!

JD

Welcome Bret. You have posted some great stuff on 23hq.

JD