(Large photos) Night shots problems with the Sigma 18-200 OS and 18-55 (non IS)

Started Jan 3, 2009 | Discussions thread
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bvphotos
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(Large photos) Night shots problems with the Sigma 18-200 OS and 18-55 (non IS)
Jan 3, 2009

So my long exposure night shots are terrible. They look blotchy, with city lights bleeding outside the edges of windows. I took a bunch of them recently with my Sigma 18-200 OS, and here's an example:

OS off, on my Feisol tripod with the Giotto ballhead secured properly, f8, 8" exposure, no mirror lock-up. Some PP (exposure correction, and some sharpening). Shot RAW and converted to JPEG:

I've had similar results with the kit lens 18-55 (non IS), so I won't post them.

Now, neither lens is supposed to be stellar, but I certainly expect them to produce better results. Which is why I kept thinking I did something wrong. Maybe my tripod isn't stable enough, maybe I should use mirror lockup, etc. Perhaps they're all still valid, but to complicate matters, here's a handheld shot that same day with the 18-200, which I find equally bad when viewed at 100%. FL 28mm, f13, 1/100, no PP, shot RAW and converted to JPEG:

I also know that this lens is capable of taking decent shots. Like this one (28mm, f13, 1/200, RAW converted to JPEG, some exposure correction, but no sharpening):

So, any ideas what's going wrong with the night shots? My technique, exposure too long, wobbly tripod, breeze, no mirror lockup? Or is it simply that both lenses are terrible when focussed at or near infinity, and decent at closer distances?
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http://bvphotos.smugmug.com

Rebel XT, Canon 100 f2, Canon 100mm 2.8 macro, Canon 100-400 IS, Canon 50 1.4, Canon 10-22, Sigma 18-200 OS, Tamron Pro 1.4TC, Speedlite 430EX, Feisol 3402 + Giotto ballhead.

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