How Photographs are Recorded

WendyMay

Well-Known Member
How Photographs are Recorded

With most photography books comes a bunch of technical information at the beginning that most of us usually page right past. What's the sense of reading any of it? The diagrams are tough to make out and sometimes what we're looking at doesn't even apply to the type of camera we own. I mean, really. In one of the books I just purchased, there's a section called, How a Camera Sees. When I first glanced at it, I pretty much figured I'd skip it here on the forum. But then, as I read things a bit more closely, I realized how important the information actually was. In fact, what I read described the very basis of photography itself. Because of this, I've decided to leap in head first and make a go at it. Of course, I'll spice things up here so you don't fall asleep. And, as always, if you have any questions, please don't hesitate to ask. I eat this kind of thing for breakfast.

What's a Sensor?

Inside of every digital camera is a small flat piece of material that collects light. This little piece of equipment is what the entire camera is built around. It you ever open your camera up so you can see inside, perhaps by removing the lens and flipping the mirror up, you'll see the sensor. It looks like a blue/green piece of glass. You can sort of think about the sensor as the brain of the camera. It's the thing that all the effort of exposing your images goes into. To be hyper specific, contained within the sensor of a digital camera are millions and millions of tiny little dimples called photosites. These photosites act like a CD or a cassette tape do. They record things and in this case, they record light. Photons to be exact. So basically, inside of your camera is a sensor. The sensor consists of millions of photosites that collect the amount and type of light that are allowed into the camera to land on it. Once the light lands on the sensor, the camera's processor processes it and almost by magic, creates a photograph from it. This is the technical part that most of us don't really need to know. What we do need to know comes next.

How Does Exposure Work?

Now that we know how light is transformed into a photo, let's talk about how to get the right light onto the sensor. For a moment, let's pretend that it's possible to hold a functional camera sensor in your hand, right out in the open. If you aimed that sensor at a scene, do you think it would capture that scene and transform it into a wonderful photo? Probably not. The question is, why not? Well, for one, sensors are pretty sensitive things. Just by holding it out in the daylight for more than a split second, you're likely to expose it to too much light. That would make all of your resulting images nearly pure white. That's not good at all.

Let's think about how a camera works. To take a photo, you (or the camera) set the shutter speed, aperture, and ISO. Why do you do these things? Well, first things first. The shutter speed limits the amount of light that comes through the lens and lands on the sensor. You can control how long the shutter stays open. The longer it stays open, the more exposed an image will be. A long shutter speed will give you two things; first, it'll give you lots of light and second, it'll give you blur if the camera isn't perfectly still. If you set a very fast shutter speed, you'll get much less light and very little blur, if any at all. So that's the shutter speed part of the exposure equation.

Next, we'll discuss aperture. The aperture is basically the hole that's contained within your lens. By making settings on your camera, you can shrink and expand the size of the hole. Obviously, the larger the aperture, the more light that will come through and will hit the sensor. The smaller the hole, the less light. Aperture also controls something else. Something called depth of field. This is the blur that you see in the foreground and background of pictures.

Finally, we have the ISO. This is basically how sensitive your camera's sensor is. You can change this sensitivity very easily. By increasing the ISO number in your camera's settings, you make the sensor more sensitive to light. By lowering the number, you're making is less sensitive.

So really, the fact that light merely hits a sensor is only a small part of the story of how a photo is created. What's much more practical to understand is how you get the right light for your situation on that sensor.

I'll be discussing all of this in much more depth in later posts, but I'm glad I got some of it out. You can use this as a primer.
 
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