Depth Perception- uses both eyes- how does a camera lense allow depth perception?

Watching a show about our eyes last night, I heard that with the slightly different images our eyes capture our brain puts them together and that is the basis of depth perception. How, then, with cameras, can we still gauge how far away things are in pictures and in movies, since cameras have only one image to capture? Is it mainly just using reference objects that we know the size of roughly, like humans or cars to guess how far something in a picture is? Did that make any sense?

Yup, you pretty much have the answer. Without stereoscopic (with two eyes) vision, the brain falls back to other cues like relative size (things farther away look smaller) and occlusion (things behind get partially hidden by things in front). Lighting also plays an important role, like the location of highlights and shadows. There are also a few more subtle cues, like objects appear hazier and slightly bluish when they are far away.

You have good understanding of what is going on with a photo. The camera's aperture is adjusted to take advantage of the amount of light present, the more light, the smaller the the aperture opening, this gives a wider depth of focus and helps in judging depth of objects in the photo.