The Rule of Thirds, Part 1--Spaces

Click on flower to see the image without lines
Rules aren't really rules in photography.  That's the first thing  you need to know about the "rule of thirds."  Even before I define it, you need to know that.  Even the rule of thirds is just an approximation of the "golden ratio," which artists have used in composition since the Renaissance. Generally speaking, the golden ratio corresponds to patterns seen in nature, and it seems to coincide with the way the human mind perceives beauty.  But especially in photographic composition, there's no need to compose precisely by the golden ratio, so we approximate it with the "rule of thirds."

Imagine your viewfinder divided up into thirds both vertically and horizontally so that it contains 9 equal segments, or just look at the above photo.  The spaces, lines and intersections of this grid can be very useful in composition.  When you compose with the subject smack dab in the middle of the frame, the composition often (not always) seems too direct and less pleasing.  So photographers generally frame their compositions with the subject off center.  When the subject takes up a large part of the frame, as with the above flower, I often fill 4 of the 9 frames with the subject, leaving the outer 5 for other parts of the image.  When you compose this way, it is often good for the subject to face into the frame.  This gives the subject room to look or "move."

Old House
Old House in Sykesville, MD
Of course, there are good reasons to break this rule.  Sometimes you want to emphasize the symmetry of your subject, so you can "bulls eye" your composition.  You may want to face the subject out of the frame to make it seem like your subject can't wait to get out (think of a picture of boat fleeing an approaching storm).  You're the artist, not the rule.  Make decisions based on you're artistic vision, and let the rule help you along the way.  But the rule is simply a tool for you to use, not a rule to follow.