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Old Mar 21, 2007, 10:43 AM   #21
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shadow-wolf wrote:
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I've taken quite a few photos both sets so I don't think the difference is camera shake.
Are you sure about that? What were your shutter speeds for the two images and how far were you zoomed in?

If you don't see any obvious focus point in the blurry shots (further away or closer to the camera compared to the ball you were focusing on), it's more likely a camera shake issue causing the blur. You may be learning to sqeeze the shutter button more smoothly as you get used to the camera.



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Old Mar 21, 2007, 4:16 PM   #22
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JimC wrote:
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shadow-wolf wrote:
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I've taken quite a few photos both sets so I don't think the difference is camera shake.
Are you sure about that? What were your shutter speeds for the two images and how far were you zoomed in?

If you don't see any obvious focus point in the blurry shots (further away or closer to the camera compared to the ball you were focusing on), it's more likely a camera shake issue causing the blur. You may be learning to sqeeze the shutter button more smoothly as you get used to the camera.


focal length was 18mm and shutter speed 1/30s image stabilisation on for both shots. I also had some other shots of the pool table I'd done on a tripod which exibited the same blurriness/softness.
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Old Mar 21, 2007, 4:23 PM   #23
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Are you sure you're getting a good focus lock (half press the shutter button and wait for the steady lock indication before pressing it the rest of the way down)?

Are you sure you are focusing on what you think you are (select a focus point, and make sure that's the one it's using when you lock focus with a half press)?

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Old Mar 21, 2007, 5:50 PM   #24
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JimC wrote:
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Are you sure you're getting a good focus lock (half press the shutter button and wait for the steady lock indication before pressing it the rest of the way down)?

Are you sure you are focusing on what you think you are (select a focus point, and make sure that's the one it's using when you lock focus with a half press)?
I think so. The focal point indicator was on the ball for each shot, and it was the same focal point, the center one on the camera. I'd be quite happy for the fault to lie with me cause it means that my gear isn't faulty. To be honest though, I've never been particularly impressed with this lens quality, being a basic kit lens I can't expect too much from it I guess. I'm actually wondering if there's something like a 18-70+mm F2.8 - F4 type lens available that would make a good replacement for a general purpose lens, I could cope with lose a bit of zoom for a brighter lens. Baring that, then I might have to pony up the money for a 18-50mm F2.8 for indoors and low light.
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Old Mar 22, 2007, 3:57 PM   #25
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shadow-wolf wrote:
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Another strange thing has happened, in the course of fiddling around and testing with the lens, it seems to have dramatically improved for no apparent reason.
It seems to me that, if you just keep fiddling around, your camera will eventually become perfect.

Either that, or it may revert to what you had before.
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Old Mar 23, 2007, 2:16 PM   #26
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shadow-wolf

I think you're probably trying too hard to find a fault with your equipment.

Almost any lens is going to have a touch of edge softness at closer ranges like some of your first samples,

I'd also expect most lenses to lose some sharpness stopped down to smaller apertures (higher f/stop numbers) like some of your samples.

Most lenses are sharpest at around 2 or 3 stops down from their widest available aperture.

Anytime you get a new camera or lens, it can take some getting used to. So, I wouldn't jump to any conclusions about your equipment until you have a chance to use it more.

In most cases, the photographer's skill is going to be the limiting factor in getting better images, not their equipment (although equipment can play a role, depending on what/where you're shooting, and what the purpose is for the images).

Suggested reading:

http://www.prime-junta.net/pont/Pontification/ba_Don't_Be_A_Bozo/a_Don't_Be_A_Bozo.html

(and I'm not trying to imply that you are, it's just a very good read for someone with a new DSLR).


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Old Mar 26, 2007, 6:35 PM   #27
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Bob Nichol wrote:
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f/19 may be getting into diffraction limits. How does the lens perform if you keep the aperture around f/8? Have a look at* http://www.lonestardigital.com/apert...ion_limits.htm and http://www.cambridgeincolour.com/tut...hotography.htm for details.
I tend to agree with Bob. I own the Sigma 18-200 which is a fine walk around all purpose lens that can be extremely sharp when you understand the limitations of the lens and this applies to any lens. The optimal sharpness of many lenses is generally 2-3 stops down from maximum aperture. Once you get up in to f19 to f32 you start having to deal with serious diffraction problems. These problems can be dealt with if you understand the nature of the beast. Product photographers often shoot a f 128.0, but they do so by shooting multiple images on the same frame. I suggest that you increase your shutter speed to bring the Sigma down to acceptable levels of around f8.0 to f16.0 and optimally on that lens at f11.0. Contrast also plays a major roll in perceptible sharpness. You really have to understand how to read light and bring out the best in your images by doing so.

http://www.pressbook.com/homebook.as...&owner_id=5144
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