I took the shot above at Navy Beach at Mono Lake today as an example of creating a sense of scale - and size - in a photograph. Without the photo of me below as a reference, these stone structures (the same in both photos) would look gigantic.
Keep in mind that the angle at which you shoot, and the lens you use, effects the scale and apparent size of a subject in a photograph.
Both shots were taken with my Canon 17-40mm lens on my Canon 5D Mark III. All my gear is listed on my gear page.
I hope to see you on one of my workshops. We talk about this kind of stuff.
Explore the light,