Light, Camera, Zoom!

I'm picking up from the entry on the "Fundamentals of Photography", so be sure to start there if you have missed it! ;)

The first concept that I had trouble wrapping my head around was the concept of field of view. The term comes into play when we talk about the second most popular topic for stalkers and paparazzis: zooming. I'm guessing that the first would be infrared or x-ray photography for the hentai ojisans out there. =P At any rate, humor me while I try my best to explain the mechanics of zooming without getting confused all over again.

So, let's think for a moment about the effect we get when we press that trusty ol' zoom button on our cameras. What does it look like is happening? Well, to me it looks like the camera is basically taking a portion out of the center of the image and bringing it closer to me. *DUH*, you might say. Well, the subtle point I was trying to make by emphasizing the phrase "center of the image" was that zooming is NOT the same as taking a picture of the object when you're physically up close to it. The distinction arises from the fact that zooming

involves putting the lens, but not the screen on which the image gets projected on, closer to the object than it really is. In physics speak, what we're trying to do here is increase the focal length. So, why does increasing the focal length magnify the image, you ask. It's quite simple actually. To explain this phenomenon, we have to introduce that term I talked about at the top of this entry: field of view.

Field of view is the area which you're actually able get portrayed as an image in the viewfinder of your camera. In real life, the field of view defines what you can actually see with your eyes. For example, you can hopefully see what's directly in front of you, and if so, chances are good that you can also see things that are slightly off to the side, but you damn well can't see directly to the left or right unless you turn your head around. So the field of view is defined by the horizontal and vertical angles that you have visual access to.

So how are focal length and field of view related? Well, when you increase the focal length, the field of view shrinks. Think about it. The screen on which the image is projected on is of a finite size, and as you move the lens away from the screen to increase the focal length, the light rays will end up getting refracted by the lens sooner. This increases the distances traveled by the refracted rays before they hit the screen. As a result, the light rays will get projected further out on the screen, hence producing a magnified image. Now, as you zoom more and more, the rays that get refracted at higher angles will soon be out of reach by the fixed area of the screen. This leaves you

with only the rays that don't get refracted as much. So if you think about it, when you zoom, you're essentially bombarding most of your screen with rays of light that are exiting the lens at more or less parallel angles to the horizontal axis. In other words, you're throwing away much of the perspective information that would have normally been captured, so your image will no longer have much depth to it. That makes image captured through zooming, different from that captured up close.

Depthless or not, people can't seem to get enough this zooming business! Not only do we have cameras with optical and digital zoom features, you could literally buy lenses that let you zoom further and at higher qualities. They don't come cheap, and they're a pain in the ass to carry around, but they seem to sell pretty well. So something's gotta give, right? =P

There's also the subject of radial distortion, namely pin cushion and barrel distortions, that are often brought up while talking about the various phenomenon related to lenses. Well, unfortunately, the class never really dove into the details of what exactly causes these effects. The gist of it, however, is that the lens you have may be screwing your image up, but if you believe your bottle is half full, these distortions can become cool visual effects! I say either curse incessantly at your crappy lens or bask in glory as your friends drool at your artistically shape-shifted imagery. ;)

Phew! Allllllrighty! This completes the "Fundamentals of Photography" entry. Next time we'll talk about the color spectrum and the human eye! Stay tuned!