Concepts of Composition

Natural Framing
http://www.photographytips.com.au/natural-framing-in-photography/

Natural Framing
http://www.photoxels.com/tutorial_frame.html

Negative Space Online Exhibition
http://c4fap.org/exhibitions/2009NegativeSpace/index.htm

Mind's Eye Information Page
http://c4fap.org/cfe/2009mindseye/mindseye.asp

Merge & Converge
http://digital-photography-school.com/how-to-overcome-the-problem-of-converging-verticals#hide

Natural Framing
http://www.brighthub.com/multimedia/photography/articles/956.aspx

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