When viewing a two dimensional photo, our sense of depth is aided by various depth and distance cues. We can use these clues to our advantage when they are present in our scene.
Shadows offer obvious depth perception clues. Photos taken at sunrise or sunset take advantage of long shadows to enhance the apparent depth of the scene.
When one object hides or partially hides another from view, the object that is hidden is seen as being farther away
The air contains microscopic particles of dust and moisture that make distant objects look hazy or blurry. This effect is called atmospheric perspective, and we use it to judge distance. Haze, mist, and pollution can provide important depth cues
A texture gradient arises whenever we view a surface from a slant, rather than directly from above. Most surfaces such as the ground, a road, or a field of flowers have a texture. The texture becomes denser and less detailed as the surface recedes into the background, and this information helps us to judge depth.
Linear perspective refers to the fact that parallel lines, such as railroad tracks, appear to converge with distance, eventually reaching a vanishing point at the horizon. The more the lines converge, the farther away they appear.
Relative size: with objects of equal size, the one that is farther away will take up less of your visual field of view than the closer one. This is because we perceive an object as staying the same size no matter how father away it is.
Size of familiar objects. Through experience, we become familiar with the standard size of certain objects, such as houses, cars, airplanes, people, animals, books, and chairs. Knowing the size of these objects helps us judge our distance from them and from objects around them.
We perceive points nearer to the horizon as more distant than points that are farther away from the horizon.