Originally Posted by
dagray
I would like to add to this that photography is all about light. Large apertures let in lots of light, but also create a shallow depth of field (either the front, middle, or back plain of the photo will be in focus with the rest out of focus), and conversely really tiny apertures cut out light, and create a photo with all the photo plains in focus.
Light can detract or enhance a photo (especially a portrait) with a portrait you don't want a super bright spot on the chest or hands if you want the face to be your subject as those bright spots will draw your eye away from the main item the photographer is trying to show.
Light can enhance a photo by illumination a section of a photo or sometimes a shadow can enhance the photo (shadow being lack of light) Look for example of a portrait where half the face is lit and the other half is in shadow.
Changing your angle to the light (notice the key element is still light) can change perspective, mood, and even composition of a photograph.
Dave