This is one of my oldest photographs, taken while I was a freshman in high school. It's of the family dog, Prince, who appears to be smiling and ready to romp. It's special to me--and only to me--because it reminds me of my youth.
Photography is, by definition, the art of painting with light. What often gets overlooked is the degree to which it's also the art of recording impressions of time. At the most basic level, every image is affected by your choice of shutter speed--the period of time your film or digital sensor is exposed to light. A short shutter speed freezes motion, assuming there was motion to freeze, of course. A long shutter speed does the reverse: Objects in motion blur. Static objects look...static; that is, unless the camera is moving too, in which case the entire image can be blurred; sometimes artfully, sometimes not.
Whatever you capture is a photographic representation of how that particular subject or scene looked during that one brief instant of time. With street, candid, or sports photos there's the reality that you captured a unique moment in time that will never happen again in exactly the same way, with the same light, subjects, and composition. With photojournalistic photography the unique moment in time may also be historic. Think of the classic photograph of Jack Ruby caught in the act of shooting Lee Harvey Oswald.
Here's a photo of Texas bluesman Sam "Lightnin'" Hopkins, performing at the Ash Grove in Los Angeles. It has some historic value in that the Ash Grove burned to the ground in 1973 and Hopkins died in 1982. His style and music, however, live on.
Then again, even an obscure photograph can be historic by providing a look back in time. That's why most people take photographs: to record a time, place, person or event that's special to them. When such photos transcend their appeal to a small group of individuals and begin to appeal to the world at large they rise to the level of art. That's an important distinction for those of us who are actually trying for art. We have to do better than anonymous photos that could have been taken any time, anywhere, by anyone. That means creating photos that suggest a special moment combined with an individual point of view.
Take still life photography for example. A common way to suggest life (which, after all, is a time-sensitive state of being) when photographing motionless objects is to show evidence of something the passage of time. Rust and wear suggest age and constant use. A fallen leaf suggests something that just happened. Steam rising off the surface of a hot liquid suggests something happening now. You can also evoke a sense of time through your lighting. Low light and long shadows suggest morning or evening light. Soft overhead light suggests the hazy midday sun or open shade. Add deep shadows and suddenly you're in a small room with a small skylight overhead. What applies to still lifes applies just as well to other genres of photography. Combine the right light with the right time and the right timing and your odds of a memorable photograph are greatly increased. The trick, of course, is knowing when the moment is right.
These are my observations. You're sure to have some of your own. If not, I'd suggest that before you raise camera to eye you give some thought to the moment in time you're trying to capture. What's special about it? What are you trying to remember? What do you want others to see? If you can convey what's special about a moment in time then you're well on your way to producing memorable photographs.