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06-15-2009, 10:08 AM   #1
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Is my 50-135 F2.8 a bad copy, With photo samples

Hi everyone

Here is 3 photos taken at 135mm
1 taken at F2.8, 1 taken at F4 and one taken at F5.6

At F2.8 I think the IQ is unacceptable and at F4 and F5.6 they are ok but compare to my cheap sigma 70-300 they are the same

Please please can some one see these photos and let me know if my lens is a bad copy

Thank you

F2.8
HTML Code:
http://www.flickr.com/photos/geovien/3629671958/sizes/o/
F4
HTML Code:
http://www.flickr.com/photos/geovien/3628861929/sizes/o/
F5.6
HTML Code:
http://www.flickr.com/photos/geovien/3628864523/sizes/o/



Last edited by Damn Brit; 06-15-2009 at 11:56 PM.
06-15-2009, 10:28 AM   #2
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What do you not like about these samples? They look sharp (where you focus; there is little depth of field) and colour is good.

Most lenses are not as good when focused this closely as they are focused at more distant objects too.

The Sigma is also known for being good at 135mm (mine was). So, what you're getting with the DA* is F2.8, build, SDM, WR, and internal zoom.
06-15-2009, 10:36 AM   #3
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DOF is thin, part in focus looks good on my screen. Are you pixelpeeping at 400%?
You can see how much you need to clean your keyboard too
06-15-2009, 10:47 AM   #4
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QuoteOriginally posted by jslifoaw Quote
What do you not like about these samples? They look sharp (where you focus; there is little depth of field) and colour is good.

Most lenses are not as good when focused this closely as they are focused at more distant objects too.

The Sigma is also known for being good at 135mm (mine was). So, what you're getting with the DA* is F2.8, build, SDM, WR, and internal zoom.
At F2.8 I think it looks very soft. I don't know if this is normal or not.

06-15-2009, 10:57 AM   #5
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I don't know - looks pretty sharp to me. Maybe try a focus test chart to see? There's a printable one here: http://FocusTestChart.com/focus21.pdf
06-15-2009, 11:32 AM   #6
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People say at 2.8 the image would still look sharpe but my copy seems to be not that great at 2.8
06-15-2009, 11:41 AM   #7
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I also don't see anything wrong with the images. And my basis for comparison is a set of primes.
06-15-2009, 11:44 AM   #8
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QuoteOriginally posted by kristoffon Quote
I also don't see anything wrong with the images. And my basis for comparison is a set of primes.
Erm maybe I am expecting too much. what happen is I compare the image with my sigma low end lens and they seems to be as good as the pentax so I am very disappointed about this fact.

06-15-2009, 11:54 AM   #9
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I just examined your f/2.8 image closely. At this focusing distance (1 Metre? ) the depth of field is very shallow. The detail is excellent in the focus plane. I also think that you are taking the image under tungsten light which is known to shift the plane of focus slightly.
06-15-2009, 12:00 PM   #10
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i concur. i doubt you'd see much of a difference with any cheap/expensive comparison in that scene.

take it outdoors or try it with better light.
06-15-2009, 12:10 PM   #11
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You haven't made clear if you understand what DOF is and why people have mentioned it here, so I'm guesisng you don't.

Your f/2.8 looks extremely sharp to me, but *only* in the very small area that is actually in focus. Most of the image is out of focus. And this is totally normal and indeed completely unavoidable for f/2.8 - that is what is meant by shallow depth of field. You'll have on part of your image in focus, the rest not. The larger the aperture (ie, the lower the f-number), the less of the images that will be in focus.

So, only the couple of keys and bristles of the brush are in focus. But try to find another zoom lens that can produce a sharper image of those keys and bristles than that at f/2.8 - I doubt you will succeed!
06-15-2009, 12:28 PM   #12
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QuoteOriginally posted by Marc Sabatella Quote
You haven't made clear if you understand what DOF is and why people have mentioned it here, so I'm guesisng you don't.

Your f/2.8 looks extremely sharp to me, but *only* in the very small area that is actually in focus. Most of the image is out of focus. And this is totally normal and indeed completely unavoidable for f/2.8 - that is what is meant by shallow depth of field. You'll have on part of your image in focus, the rest not. The larger the aperture (ie, the lower the f-number), the less of the images that will be in focus.

So, only the couple of keys and bristles of the brush are in focus. But try to find another zoom lens that can produce a sharper image of those keys and bristles than that at f/2.8 - I doubt you will succeed!
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.
06-15-2009, 12:41 PM   #13
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The fact that the 50-135 shoots f/2.8 and the Sigma doesn't means you do see a real difference right away.
06-15-2009, 01:54 PM   #14
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QuoteOriginally posted by m42geo Quote
... 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. ...
Man, I think you are missing big point here. You will need to define your expectation. There's no way any lens can take a "sharp" photo across the frame in your scenario (with variant depth in the scene). It's against physics, or at least the physics current imaging system's built on.

If you want to test formally, print out a chart, put it on a wall and take a photo straight at it. Make sure the chart is in a hyperpane of the lens. In this setup, all of the chart would be "in focus" (supposedly if you do it correctly) and crappy lens would have bad resolution on the border of the frame. At center, I guess there shouldn't be much of a difference whatever lenses you use.
06-15-2009, 01:57 PM   #15
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QuoteOriginally posted by m42geo Quote
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.
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.
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