Photo sharpness, am I imagining things?

japvdk

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Hi all!
After a lot of online research, I recently bought a new lens, the sigma 18-250mm f3,5-6.3DC Macro OS HSM. However, since having bought this lens, I haven't been pleased with the overal sharpness of the images. It is not that the pictures are horribly out of focus, but they all seem a little soft. Of course, the easiest explaination would be blaiming my new lens, but I am reluctant to do so. Some online research gives me a vast array of possible explainations, one of which is too high expectations. I have attached some pictures I recently took, and I hope you can tell me if they are not as sharp as they should be. I have not zoomed in.

IMG_0896 — Postimage.org (f10 1/100 iso 100)
IMG_0394 — Postimage.org (f11 1/100 iso 100)
IMG_1378 — Postimage.org (f10 1/100 iso 100)
IMG_9753 — Postimage.org (f14 1/60 iso 100)
IMG_9025 — Postimage.org (f22 1/15 iso 100 tripod)
IMG_1573 — Postimage.org (f10 1/8 iso 100 tripod)

For the last two, I might have overestimated my tripod (very old), but for the other two the shutterspeeds seem fast enough for a hand held wide angle shot.
Thanks for your help, I hope the links work
 
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Parker219

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Did you shoot these is jpeg or RAW?
 

Braineack

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looks like a very bad copy of the lens.
 

table1349

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Here is the conclusion from DP review on that lens.

The Sigma 18-250mm F3.6-6.3 DC Macro OS HSM is one of the best of the current bunch of SLR superzooms, with decent optics, fast autofocus and effective image stabilization. It's a reliable performer, and its close-up capability is handy too.

Good for: Photographers looking for a compact, lightweight, all-in-one general purpose and travel lens.

Not so good for: Anyone unwilling to sacrifice image quality for convenience


IQ is the compromise you accept with a super zoom.
 
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japvdk

japvdk

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@Braineack, what do you mean? That there is something wrong with the lens? Would you recommend going back to the store?
@gryphonslair99 I am aware of the setbacks of super zooms, it was a difficult decission, but do you really think that the image quality would this bad? When I was researching the lens I got the impression the differences in image quality between lenses where differences that could only be seen by trained eyes, and mostly at the extremes of camera settings, certainly not at apertures of f10. But I might be wrong of course.
 

astroNikon

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most people can't handhold 1/1o0 much less 1/60 for sharpness.
 

fmw

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The longer the zoom range, the more the compromise in image quality. You can't expect this lens to perform with one that has a 2X or 3X range.
 

Light Guru

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The quality of the image posted is about what I would expect from a lens that is trying to be a all in one lens.

When something or someone tries to do everything the quality is never as good as when you specialize in something.
 

HughGuessWho

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You must concider that the vast majority of reviews found on the Internet are written by those that are clueless
 
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japvdk

japvdk

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My aunt has a similar lens, and I always think her photos are really sharp. I'd rather hear that I need to use shorter shutterspeeds, a different aperture, and so on.. But the general conclusion seems to be that I can't hope to get sharp pictures with my new lens. What a sad conclusion...
 

Light Guru

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My aunt has a similar lens, and I always think her photos are really sharp. I'd rather hear that I need to use shorter shutterspeeds, a different aperture, and so on.. But the general conclusion seems to be that I can't hope to get sharp pictures with my new lens. What a sad conclusion...

Well you can certainly try those things.

The things people have said here are the reasons why a pro photographer would not use the lens. That does not mean others can use it with fine results.
 

SquarePeg

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Try a faster shutter speed with a wider aperture.
 

The_Traveler

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I looked at three of these, they were shot at 18 mm and a very small aperture and under lighting conditions that would tax any situation.
The images hadn't be sharpened in post-processing

The very end of any zoom lens' travel is generally not the best spot for sharp images.
The smallest aperture induces aberrations.
Most images need sharpening.
The best images are made when the light is diffuse but directional, not overhead and not in total shadow.
My guess is that, as you learn more about shooting, you will get better results from this lens.
 
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japvdk

japvdk

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@The_Traveler Wow great so there are things I can do about it, great! I wouldnt have thought that f10 is too small of an aperture. I read somewhere that f8 is mostly the best for sharp images and so I thought I'll stay in that ballpark but use a little smaller aperture fore landscapes, to get a larger depth of field. But if I understand it correctly the lessened sharpness of a smaller aperture negates the effects of a larger depth of field?

Post processing is something I am just starting to play around with (using gimp2) and I havent found the sharpening tool yet haha.

I dont really understand why lighting conditions would effect the sharpness. I understand that it can make the exposure more difficult for a pretty picture, but how does it effect sharpness?

Thanks so much for everyones help, it is good to learn where I made mistakes!
 

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