You see photos everywhere. Browse the web: you see photos. Open a newspaper: you see photos. Drive to work: you see billboards with smiling models… in photos. And that’s just the situation for normal people. It’s even worse for us photographers, who live and die for photos. So how can you pick good photos out of the flood of them you see each day?

People are among the most common subjects in photography. People in motion, people in poses, people on the street. And people are important in pictures even when they’re not the subject, by enlivening the picture or showing scale. But do you know what not to do when photographing people?

The standard formats (height/width ratios, also called aspect ratios) for photographs have evolved over time. But some formats have proven over time that they’re best left untouched, and so camera makers stick with them. So let’s take a look at the most common aspect ratios for digital images—these ratios are also the ones produced by digital cameras, and photo labs and photo frame manufacturers expect them.

Image composition is a critical element that can elevate—or deflate—the value of your photographs. Thus it’s something that you should never underestimate.