Fundamentals of Photography

The classes are going pretty well, and many of the questions I've had about photography have been getting answered one by one. This is kinda cool given that I didn't even know that I was going to get an education on photography to begin with. ^^; The answers came in the form of physics lessons, and I have to say it's been ages since I had revisited optics. As a matter of fact, it almost feels as if this is the firs time I'm being exposed to these concepts. My guess is that my previous encounters with these subject matters were more mechanical in nature. In other words I was taught how to solve physic problems, not to truly understand what kind of a real world phenomenon was taking place. We need to reform our education system, dammit! Hmm... I suppose I could have been slacking and just didn't keep up with the work at that time, too... heh heh... Anyway... Lemme stop blabbering and get on with our first real topic of the blog: Fundamentals of photography.

The fundamental concept of photography on which all other facets are based on is the fact that a camera is basically a box that sits around collecting light rays that travel through a hole. Depending on the angle at which the light enters the hole, it'll meet with some plane behind the hole at a certain spot. The collection of light rays at these spots result in an image that we call a photograph. The physical hole through which light rays enter is called the

aperture, and the point at which the aperture resides is called the center of projection. If you put a screen behind the aperture, let light become projected on it, and measure the distance from the center of projection to the screen, you'd get what is known as the effective focal length of the camera. Now, if you were put a film in place of the screen, you'll be able to get yourself an imprint of the image projected on it. See, cameras aren't that complicated. ;)

An unfortunate characteristic of this imprint that a camera produces, however, is that it is incapable of accurately encoding the angle and the distance between and among the objects portrayed in the image. The reason is simple; the image is 2D and the real world is 3D. However, what's really interesting is that when we humans look at these images we're somehow able to make sense of it in our heads as to what thse objects really look like and how they would be positioned in real life! It turns out that our brain does a lot of these work for us to keep our sanity intact. Of course, the brain is only able to do this because it has been acquiring a lot of information through the eyes for a long time. It isn't without fault, however, as you can find instances where the information gathered can fool us into perceiving things incorrectly as well. The Muller-Lyer illusion, is a famouse illustration of such consequences.

So with the help of our brain, these flat images that we've managed to capture, turn out to be pretty neat things to have around. Given its usefulness, our forefathers probably thought this imaging device we call camera was worth spending some time to improve upon. One of the tricky design constraints that they noticed was that, the hole needed to be small enough to prevent too many rays originating from the same physical object from entering, yet large enough to let all the rays we want through. The problem with letting in too many rays of light reflected from the same physical object was that, the rays would enter the hole at different angles and scatter on to multiple

points on the screen, resulting in what we commonly refer to as a blur. So they managed to find a good size hole small enough to let the minimum number of rays in to produce a sharp image, but alas, with so little light passing through a hole of such small size, it was necessary for the photographer to stand around waiting for enough light rays to pass through the hole to produce a reasonably bright image.

This brings us to another important element of photography: exposure. Exposure is basically the time a photographer spends collecting light rays on the film or, if you're using a digital camera, a CCD or CMOS sensor array. Have you ever wondered why photographs taken at night on a digital camera without flash sometimes come out to be blurry? Well that's because the camera opted to use long exposure in order to collect as much light as possible, but since you couldn't keep your hands steady for that entire duration of the exposure, light rays got collected at multiple spots and produced a blurry image. Next time invest on a tripod, or keep a few tablets of diazepam handy. ;)

So to improve upon this pin-hole model, the next batch of innovators used a lens to grab rays of light that would have otherwise not passed through the hole, and directed them so that they would. This allowed the collection of more lights without long exposure.

Now, with the lens in our camera, we have a new measurement that we need to talk about; the focal length. The focal length of a lens is the distance from the optical center of a lens to the intersection point of all light rays that are parallel to the horizontal axis on which the lens stands once they get refracted. I know that sounds confusing, so take a look at these diagrams and see if they make more sense. Notice that this is different from the effective focal length previously discussed.

Unfotunately, plopping in a lens didn't only bring about a solution to our problem, but also presented some challenges. The artifact of having a lens was that, we now needed to care about focus. What the hell does that mean? Well, depending on the angle at which rays of light reflected from various physical objects got bent by the lens, they would end up converging on several different planes. It was no longer possible to just have the film residing on one plane recive equally focused rays of light to produce a sharp image of the entire captured scene. You may have lights converging to a single point behind where the film lies, which made the film collect the yet-to-be-focused rays of light and end up producing a blurry image of the object. So your entire image may not get blurred out, but objects located at different distances from the camera would end up with varying degrees of sharpness in the final photograph. There's even a cool term for the circular area of blurring you get when an object isn't focused! It's called circle of confusion. How cool is that?

The "simple" workaround for this problem is to shrink the aperture. The reason why this works requires us to think of the very reason why a blurry image gets produced in the first place; you're letting in more than one ray of light from the same physical object, and those extra rays are being projected onto multiple locations. So when you shrink the aperture, you're letting less of the rays in, and, as a result, decreasing the number of multiple projections that can even occur. But, this turns out to be kind of an ironic way of solving the problem, because it's going against the whole bloody reason we went with a lense in the first place: brightness. You see, when we have a smaller aperture, the amount of light that gets to pass through it, and, ultimately, the lens, is less than before, thus requiring more exposure to make up for it. Sounds like we're going around in circles, no? Well, the good news is that people have found aesthetical appeal in this artifact. They call it the use of the depth of field effect. Depth of field is the range at which the objects stay focused to

the naked eye. So when you talk about the effect of depth of field in your photograph, you're basically talking about selecting a set of objects that you'd like to keep in focus and another set of objects you'd like to have blurred. Hey, when the scientists are down and out, artists are always there to cheer'em up, I tell ya. ;)

Oook... So... This entry got super long... and I still have another topic to cover. Why don't I stop here, and talk about our next topic in a new entry? Alright? Stay tuned!