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06-15-2009, 02:03 PM   #16
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I would expect that the Sigma would be just as good; it's known to be good at 135mm and other short focal lengths.

So the Sigma is a very good 70-135/4-4.5 lens with decent build quality, a rotating front element, and an extending zoom, and the Pentax is a very good 50-135/2.8 lens with internal focus and zoom, SDM, and weather sealing. If the Sigma is $150-200, there is no way the Pentax will cost $200

F/2.8 makes the lens signficantly more expensive. That is why most people are happy with slower lenses because they are much more affordable and do not miss out on IQ at common apertures (but miss out on other things I described).

06-15-2009, 02:06 PM   #17
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QuoteOriginally posted by Charles Hueter Quote
Would you mind posting a few examples from your Sigma? If we knew what your basis for comparison is, our comments might be more useful.
This is the photo taken from my sigma set at 135mm F4

Flickr Photo Download: sigma 135mm at F4


Doesn't it look at good at the DA* 50-135mm set at F4 at 135mm??
06-15-2009, 02:46 PM   #18
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QuoteOriginally posted by m42geo Quote
Doesn't it look at good at the DA* 50-135mm set at F4 at 135mm??
That's not a subject where it would be easy to tell, since there is not a lot in focus, and what is in focus is only toward the center, so e can't see how much better the Pentax would be toward the edges had they been in focus. And you didn't focus on the same spot, making exact comparisons of specific spots impossible. Nor is the scene exactly the same - the Sigma is actually at 170mm, not 135mm, giving it greater magnification and hence the illusion of greater resolution. Also, the Sigma is at f/4.5, not f/4, giving it more DOF (I doubt the Sigma is capable of f/4 at 135mm). And the 50-135 shot is noticeably overexposed - highlight detail is lost. That's not the fault of the lens; the flash system can't perfectly account for reflections, especially at that range.

But, since you asked: look at the little white balls on the ends of the bristles of the brush. Find the sharpest one on the Sigma, then on the Pentax. I'd say the Pentax wins pretty handily, if I am to believe any of those balls should have been in focus on the Sigma.

Is it the sort of difference that's going to jump out and grab you by the throat on every single shot when viewing at typical screen sizes? Of course not. And if you had been misled into thinking that would be had the idea that it would, well, no wonder you're disappointed. The Sigma *is* a pretty good lens already - if you don't need the f/2.8 or 50-70 range. And as others have noted, you're comparing the Sigma's best focal length against the Pentax's worst. It's only worth spending that kind of money on the Pentax if those slight improvements are worth it to you - or if you shoot f/2.8 a lot.
06-15-2009, 03:03 PM   #19
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Tell you what I think the pentax looks great....I'm gonna get me a 50-135!

but seriously everyone has said it. Todo a proper edge comparison you need something flat, and you also need to be exactly perpendicular to it.
...thats where the brick wall test came from

06-15-2009, 03:52 PM   #20
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QuoteOriginally posted by m42geo Quote
Of course I know what depth of field is and I do understand 2.8 only have very small focus area. What I was talking about is that people keep saying this lens is great even wide open and I just feel is really not as great as I was expecting.

But since most people told me this is normal then I think I was expecting a bit too much.

I was just expecting to see real different right away since I paid 500 extra for this lens then the sigma 70-300.

So in short, the sigma 70-300 for 100 is a super good price.
The photo looks sharp, but I do see some quite a bit of CAs. Shoot RAW and photoshop out the CA and it should look fantastic (although the K-7 will do it IN CAMERA )
Can't wait to get my copy!
06-15-2009, 04:06 PM   #21
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QuoteOriginally posted by GLXLR Quote
The photo looks sharp, but I do see some quite a bit of CAs. Shoot RAW and photoshop out the CA and it should look fantastic (although the K-7 will do it IN CAMERA )
Can't wait to get my copy!
K7 cost too much, in the UK it is going to sell at 1200 which is far too expensive.

Also pentax are incraseing the price for lenses as well. I don;t know if pentax will still have the market.

I bought my K110d 2 years ago was because of it only priced at 250 with the kit lens.

But if I am to buy a DSLR now I would go for nikon.
06-15-2009, 04:15 PM   #22
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QuoteOriginally posted by m42geo Quote
K7 cost too much, in the UK it is going to sell at 1200 which is far too expensive.

Also pentax are incraseing the price for lenses as well. I don;t know if pentax will still have the market.

I bought my K110d 2 years ago was because of it only priced at 250 with the kit lens.

But if I am to buy a DSLR now I would go for nikon.
best of luck with that. Be sure to sell your 50-135* to someone who will make good use of it.

Nikon never raises their prices...
06-15-2009, 04:17 PM   #23
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The lens looks good, but try a few focus charts and check for centering problems.

06-15-2009, 04:22 PM   #24
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Please do not take this personally, but I think you may be expecting too much out of your equipment. Do you have an example of what you consider to be "acceptably sharp"? Also when looking at your photo examples, it does not strike me as soft. To me it seems that your definition of soft is "not noticably better than your sigma". However please try going out and shooting a greater variety of scenes before making a decision on your DA*.

There are many more qualities to a lens than just sharpness that justifies its extra cost. It is weather sealed, it has a non-rotating front element, it has internal focus and zooming, SDM, and a constant aperture. Also you will notice its bokeh to be smoother (due to a larger max aperture) and the colors to be different from that of your sigma.

In the end if you are dissatisfied, then there is no reason to keep the DA*. Some people will not notice a difference between a $200 lens and a $700 lens, and for them it simply doesnt make sense to be spending the extra money
06-15-2009, 05:04 PM   #25
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Anyway thanks for everyone's help. I will test this lens out more first
06-15-2009, 07:50 PM   #26
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QuoteOriginally posted by m42geo Quote
This is the photo taken from my sigma set at 135mm F4

Flickr Photo Download: sigma 135mm at F4


Doesn't it look at good at the DA* 50-135mm set at F4 at 135mm??
Rather GOOD photo for 6 MP camera. Sharp for me.

As I understand it's DA50-135 at 2.8 and 4?
http://www.flickr.com/photos/geovien/3629671958/sizes/o/
http://www.flickr.com/photos/geovien/3628861929/sizes/o/

VERY GOOD RESULT!!!! VERY SHARP. What is your problem??? Is it a joke?
06-15-2009, 08:05 PM   #27
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QuoteOriginally posted by ogl Quote
Rather GOOD photo for 6 MP camera. Sharp for me.

As I understand it's DA50-135 at 2.8 and 4?
Flickr Photo Download: 135mm F2.8
Flickr Photo Download: 135mm F4

VERY GOOD RESULT!!!! VERY SHARP. What is your problem??? Is it a joke?
Can u see F2.8 photo has very bad CA??
06-15-2009, 09:35 PM   #28
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I think if you call that very bad CA, you haven't seen many lenses shooting overexposed images at f/2.8. That's actually far better than most lenses would do in those conditions.
06-15-2009, 09:42 PM   #29
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Next time, take test shots of turds floating in your toilet. Thanks.
06-15-2009, 10:28 PM   #30
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QuoteOriginally posted by Marc Sabatella Quote
I think if you call that very bad CA, you haven't seen many lenses shooting overexposed images at f/2.8. That's actually far better than most lenses would do in those conditions.
Wow... I wouldn't normally chime in on these threads but I thought I'd check out his F2.8 image to see what was going on. That's a pretty impressive job for any lens let alone a zoom pushed to its widest aperture and longest reach. It ain't the prettiest picture in the world but the lens sure does a great job under the circumstances.

Since you were asking what a bad lens looked like here is an example. This was a bad copy of the Tamron 28-75mm F2.8 that was sent back for repair/exchange.

100% crop - 75mm F2.8 on Canon 1DmkIII
http://christopherwood.smugmug.com/photos/468914169_LcNQY-O.jpg

For comparison here is the 70-200mm lens (at 80mm because I missed when I was aiming for 75mm)... same thing F2.8 at 100% crop
http://christopherwood.smugmug.com/photos/468910555_dPndd-O.jpg

These images were all taken from tripod using a flash at 1/4 power and manual exposure
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