Luminous Landscape Forum

Equipment & Techniques => Landscape & Nature Photography => Topic started by: wmchauncey on June 10, 2007, 02:56:10 pm

Title: sigma lens
Post by: wmchauncey 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.

Title: sigma lens
Post by: mahleu on June 11, 2007, 03:42:00 am

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

Title: sigma lens
Post by: larsrc 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] (http://index.php?act=findpost&pid=122080\")

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

Title: sigma lens
Post by: :Ollivr 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.

Title: sigma lens
Post by: wmchauncey 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%.

Title: sigma lens
Post by: mahleu 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