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Author Topic: sigma lens  (Read 3710 times)

wmchauncey

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sigma lens
« on: June 10, 2007, 02:56:10 PM »

Using canon xti with sigma 55-200 mm lens, shooting 200 mm in RAW at a cell phone tower 1/2 mile away to check for clarity in Colorado.  There is no haze and no adjustments were made in ACR.

Should my image be burry at 200% magnification in ACR?  I'm just trying to determine what to expect from my lens and if a better lens would give more clarity at that distance.
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mahleu

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« Reply #1 on: June 11, 2007, 03:42:00 AM »

Do you have a UV filter on? Are you steady when you shoot?
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larsrc

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« Reply #2 on: June 11, 2007, 05:59:36 AM »

Quote
Using canon xti with sigma 55-200 mm lens, shooting 200 mm in RAW at a cell phone tower 1/2 mile away to check for clarity in Colorado.  There is no haze and no adjustments were made in ACR.

Should my image be burry at 200% magnification in ACR?  I'm just trying to determine what to expect from my lens and if a better lens would give more clarity at that distance.
[{POST_SNAPBACK}][/a]

Did you have the camera on a tripod and use shutter-lockup with delay?  What aperture did you use it at?  Photozone does indicate that the lens is capable of very good sharpness: [a href=\"http://www.photozone.de/8Reviews/lenses/sigma_55200_456/index.htm]http://www.photozone.de/8Reviews/lenses/si...0_456/index.htm[/url]

-Lars

:Ollivr

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sigma lens
« Reply #3 on: June 11, 2007, 07:39:49 AM »

how blurry is blurry? could you post a crop?
a cheap lens like that at such a focal length and an AA'ed bayer sensor AND 200% on-screen interpolation can get you soft images. If it looks good at 50% it should be fine.

O.
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wmchauncey

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« Reply #4 on: June 11, 2007, 10:08:11 AM »

I have takn this shot several times over several days at different settings always using tripod and remote without mirror lockup and without polarizing lens. The results are the same.
I just want to know if I'm expecting to much from the lens at 1/2 mile and 200% magnification in ACR.  Looks good at 50%.
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mahleu

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« Reply #5 on: June 11, 2007, 12:44:46 PM »

Ok, you have 2 possibilties.
1, the camera is either front or rear focussing
2, the lens has a problem
3, you picked a murky/hazy etc day
4, You're being too critical. If its sharp at 100% then it's probably fine
« Last Edit: June 11, 2007, 12:51:38 PM by mahleu »
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Looking for a wide fast lens (for Canon). Cheap too..
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