Monocular Cues- these visual cues only require the use of one eye, and using these different cues can help one determine characteristics such as the motion of an object, as well as its size and shape.

Relative Size- if it is perceived that two objects are closely related in size, it is perceived that the object giving off a smaller image formed on the retina is farther away.

Example: In the photograph below, these two horses are presumed to be the same size, but the horse with the black spots is smaller in the photo because it is farther away from the camera than the horse with brown spots. Thanks to relative size, one can perceive that the black horse is simply farther away rather than thinking that it is a very small horse standing right next to horse with brown spots.
https://www.flickr.com/photos/skarpi/5472158415/