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Photography Question 

Mary E. Graham 		 

Cause of circular artifact in photos


 
  CT mountain laurel
CT mountain laurel

Mary E. Graham

  
  CT mountain laurel
CT mountain laurel

Mary E. Graham

  
 
I just received my Digital Rebel XT and am using an EF 17-85 IS USM lens with it. I also had a UV filter on the lens. Taking a few pictures yesterday I noticed these 2 in my gallery having many circles in the background. The sun was behind me while shooting these photos.
What causes that? I'm new to DSLR and hoping that it is a ighting or macro effect.

Thanks for any input.
Betsy


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June 19, 2005

 

Jon Close 		  These are out of focus highlights. Entirely normal, whether film or digital. Also referred to as "bokeh." See http://www.kenrockwell.com/tech/bokeh.htm and http://www.luminous-landscape.com/essays/bokeh.shtml.

The shapes are determined by the lens design, especially the the aperture diaphram. If you look closely, you'll see that they are hexagonal - corresponding to the 6-blade diaphram of the EF-S 17-85.


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June 20, 2005

 

Mary E. Graham 		  Jon, thank you very much for your explanation, and the reference. They were both very informative.

Betsy


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June 21, 2005

 
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