Digital Home Thoughts: Photo 101 - Camera Controls

Perspective
Perspective is a property that isn't directly related to focal length; however the choice of focal length can affect it. To start off, I'll demonstrate how it affects your photos.





I've kept the wireless mouse as similar in size as possible between the two photos, but note how the radio receiver of the mouse in the photos change. It's like they've moved or changed in size between the shots! Also note the change in the shape of the mouse.

Well, what actually is happening is that the camera is capturing the differences in the distance between the objects and the camera. Let's take two objects; one in front of the other, and are a metre apart.

Now, if you took a wide angle and stood two metres away from the nearest of two objects, the difference in distance between two objects is fairly significant in relation to the camera, since one object is 2 metres away from the camera and the other 3 metres away from the camera, and thus the image recorded will portray the two objects as being far apart. The close subject-to-camera distance, made possible by the wide angle, has distorted the perspective, and thus has caused what we call perspective distortion.



However, if you stand much further away, say 10 metres away from the nearest object, and framed them the exact same way as above, thus necessitating a telephoto lens, the image recorded will show them to be quite close together. The reason now is that one object is 10 metres from the camera, and the other 11 metres. Since the difference between 10 metres and 11 metres is less significant, the image recorded will reflect this, and thus, the two objects will look closer to each other than they really are. This telephoto and camera-to-subject distance combination too has distorted the perspective, and as it has made objects look closer together than what they really are, we call this effect perspective compression.



Since many make the mistake of saying the choice of focal length causes perspective changes, I'll mention it again: the actual cause in the different perspectives is in the distance between your camera and your subject, but the choice of your focal length, hence zoom setting, means the perspective of your shot will be affected since we all tend to stand closer when using wide zoom settings and stand further away when using telephoto zoom settings.

(Incidentally, that's how the Hitchcock Zoom in cinematography is done; by changing the focal length while keeping the subject at the same size.)

So, at wide angles, we tend to get pictures that exaggerate the relationship of distances between the various elements in the photo, and at telephoto lengths, we tend to get pictures to flatten the relationship of distances instead.

Again, what can we do with this tidbit of information?