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Old Jul 27, 2005, 2:45 AM   #1
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Last week I bought the new Sigma 30 mm 1.4 lense andI am using it on a Digital Rebel. I have been testing the lense against my Sigma 18-125mm lense at 30mm, and I do not see a great improvement at the same stops. When I compare images at 4.0, 5.6, 8.0 of the same subject, the quality of the 30 just doesn't stand out.

Is there a point where the Infinity focus just does not work accurately? I did notice that the images got a slight bit better from 1.4 to 4.0, but not that great. I also noticed that when I put my Hoya HMC Skylight (1B) filter on, the images got better. Is there something wrong with this lense?

If I take images under 6 feet, they look really sharp, but anything past that, they are not very impressive.

For my testing, I have taken images of the same spot at different F stops, from a tripod, and with a cable release. Images were taken at iso 100, in Av mode.

Thanks for the help

Bill
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Old Jul 27, 2005, 8:28 AM   #2
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Do you use manual focus?

Infinity on most lens will focus past infinity. It's there for cases where people would add TC, diopter, heat expansion, or even manufacturing tolerances. The infinity point on most lens is actually slighly less on the focusing barrel...
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Old Jul 27, 2005, 12:31 PM   #3
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NHL

I used Auto Focus, with the center point selected.

Bill
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