When discussing this subject it is common to hear a lot of big words like perspective distortion, extension distortion, compression distortion, and several variations thereof. My goal with this post is not to elaborate on all the technical terms rather than to provide a simple, real-world example of how lens selection and different focal lengths can be used to change how one perceives the distance between objects within a photograph. This technique is very effective for emphasizing one component of a scene over another by changing the perceived size, and perceived distance, to a subject in relationship to the distance from the camera. 

One important note before continuing: The focal lengths discussed in this post, specifically where the angle of view is concerned, assume a 35mm (or full-frame) camera. 

Figure A: 24-85mm lens shot at 36mm focal length. Figure B: 14-24mm lens shot at 20mm focal length. Figure A and Figure B illustrate the vast difference in presentation that is possible when using different lenses and focal lengths.

To keep the composition of both photographs as consistent as possible, I tried to frame several elements as closely to the same as I could, such as the open area to the right of the cannon, the open area above the roof of the house, and the open area below the wheel closest to the camera. Neither image was cropped in post processing. 

You can clearly see the difference in how prominently the house and the cannon are presented between the two images. And depending on the viewer's perception of the apparent size of the objects, one could perceive the distance between the cannon and the house is closer together or farther apart. And as the photographer it is this play on perception that enables you to select a lens and focal length for emphasizing one subject in a scene over another. 

When employing this technique, one important element in lens selection is to consider a lens' angle of view. Figure A was photographed with a 24-85mm lens at 36mm focal length and Figure B was photographed with a 14-24mm lens at 20mm focal length. The 24-85mm lens has a maximum angle of view of 84 degrees where the 14-24mm lens extends the field of view to 114 degrees. The difference in the two angles is best illustrated in Figure B by the apparent increased width of the frame where the viewer can see more of the trees along the left and right edges. Notwithstanding the increased angle of view, the big difference is how close I was able to get to the cannon with the 14-24mm lens. In my opinion this is the real magic in playing on the perception of distance and scale. I was able to get roughly 10-to-12 feet closer to the cannon in the second photo which was necessary to maintain framing of the composition. Figure B demonstrates the big difference in perceivable scale where the foreground element was so much closer to the lens, effectively "compressing" the background into a much smaller space.

I like both images equally - one for the greater scale of the house and one for the greater scale of the cannon. But I wouldn't necessarily claim either to have a better composition than the other. "Perception" has been used quite a bit in this article and perception is very much to each as own. This is an example where one's personal preference in style might dictate which image one might hang on their wall.