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Old Sep 28, 2005, 6:31 PM   #1
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I had only ten minutes to try out my new Sigma Bigma, so I gave it a real challenge.

Camera is the Canon XT. Shot is handheld leaning against a swingset, taken just before noon, on a warm smoggy California day. Cropped, moderate sharpening, and slight contrast enhancement using Microsoft Photo Editor, ugh. (That's all I have on this laptop.)

I think I'm going to like this lens.

--M
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Old Sep 28, 2005, 6:34 PM   #2
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Oh, one more thing...

If you look closely, you'll see two smudges, one in the upper left corner, and one towards the middle right side. I was concerned until I checked the next shot that I took a few seconds later and the spots were gone.

I think they're birds that flew by during the shot!

--M
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Old Oct 1, 2005, 7:50 AM   #3
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I think you need to get those birds a little more in focus[img]/forums/images/emoticons/tongue.gif[/img]. Nice pic though... Have you tried this using a tripod/ mirror lockup etc?
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Old Oct 2, 2005, 1:16 AM   #4
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Those "birds" are actually dust spots on your sensor, nothing major and quite normal. They will only appear when using a small aperture and will vanish will larger openings such as F4, F5.6 etc. Search about a bit for how to "carefully" clean the sensor.

Nick
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Old Oct 3, 2005, 10:50 AM   #5
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Jonathan--

Didn't have the time the last couple of weeks to do a proper job on this subject, but I intend to give it a try as soon as the moon returns. This morning the skies were unusually clear, but no moon! Could have gotten a nice shot of Mars, though. Maybe this weekend I can get a crescent at night with the tripod.

This shot was a quickie test of bad conditions, and I was surprised -- particularly that I could actually handhold this lens at 500mm in a pinch. I think the softness is 99% camera shake. Of course, a tripod would be a big improvement. I'll have to work on the birds, though.

Nick --

I certainly won't completely rule out sensor dust, but I tookseveral quick shots in succession, and the others didn't have the same spots. They seem awfully large and translucent for something on the sensor plane. I may try a few controlled test shots to see.



I will post another shot with this lens under the critiques section today. Different subject, better conditions, and I think a fair result for such a wide range zoom.

--M


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Old Oct 3, 2005, 10:59 AM   #6
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Trust me...its dirt. I Photoshop around 2-3000+ images a month and I know dirt when I see it. When a dust spot is magnified greatly, it will become large and translucent as well as more circular.

It certainly isnĀ“t a bird OR a UFO before the wackos start posting! :lol:

Nick
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Old Oct 3, 2005, 11:08 AM   #7
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Yes. I should have made that point in my earlier post. It's definitely sensor dust. I have had this problem a few times, once recently on holiday... You're supposed to take the lens off in a clean environment and blow the dust out with a blower (If this doesn't work you will have to consider a lens cleaning kit). I managed to clean mine whilst walking around fisherman's wharf in San Francisco.. not a dust free zone but it worked a treat! Make sure you point the camera body downwards to avoid any more dust during the cleaning process.Looking forward to further pics on the theme mgipe[img]/forums/images/emoticons/camera.gif[/img]
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Old Oct 3, 2005, 11:22 AM   #8
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I never realized that the dust could appear so diffuse. Thanks for sharing the benefit of your experience; I appreciate it. I bought a rocket blower a while back, but haven't been brave enough to use it yet. I guess I'll have to pull out the camera manual again and go through the process of cleaning.

Then again, I could just stick to night time moon shots, whereno one would notice a few extra craters. :-)

Cheers,

--M
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Old Oct 3, 2005, 11:25 AM   #9
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Give it a go. All you need to know is here:http://www.bythom.com/cleaning.htm
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Old Oct 3, 2005, 3:34 PM   #10
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Thanks!
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