ALRIGHT ALRIGHT ALRIIIIIIIIIIIGHT! TIME TO GET NAKED!....Oh wait, wrong blog. While I won't be indulging in any form of nudity in this segment, I will be giving you the RAW (photographer's joke) facts about camera exposure. The term exposure can be summed up as the difference of a photo being too dark, too light, or just right. Dark shots are called under-exposed while extremely white or blown out shots are called over-exposed. The best way that anyone has ever described exposure to me is to think of the camera exactly as a human eye. Basically there are 3 settings that determine exposure--Shutter Speed, Aperture, and ISO.
Shutter speed, as the name implies, deals with the amount of time that a camera's shutter is open. Using the 'Human Eye' metaphor, the shutter is equivalent of one's eyelid. To demonstrate this, find something rather informative, like a business card or something, but don't read it right away. Close your eyes, hold the card up, and open your eyes then close them very quickly. This is what would be known as a fast shutter speed. Notice how little of the information from the card you were able to gather. On cameras, fast shutter speeds let in less light and, in turn, the camera has less data to use to process an image. The inverse is true for slow shutter speeds. Let's say you were just going to read the card, your eyes are open, they let in light, and you can process the light input from the card. Simple, right?
Moving right along, now we're going to talk about aperture. The aperture is the size of the opening when letting light in through the lens. On the eye, aperture is controlled by the iris and the opening that is being controlled is the pupil (wow, never thought I'd use high school bio again). When you move into a dark room, your iris naturally opens your pupil to let more light in. Adversely, when stepping outside on a sunny day, your iris closes your pupil as to not let too much light in. This also comes into play when talking about your depth of field--the distance between the nearest and farthest objects. On that sunny day, you may find yourself moving your eyes and head a little more to focus in on what you want to see. That's because you have a very narrow depth of field and can't focus on subjects at various distances. If your pupils are open, however, you get a broader depth of field. It's like standing at the edge of the forest looking out over a lake at a mountain. You get the breadth of the view. On the camera, your aperture is measured in what are called f-stops. F-stop measurements are adverse to the size of their openings. For example, a larger opening could be f/ 22 and a smaller opening would be f/ 1.8. And just because I want to leave you with a buzzword--BOKEH! Can't mention aperture without bokeh, but I'll fill you in on a later post. I need to move on.
Lastly, we have International Organization for Standardization......wait.....forget that, that's business talk. The last part is ISO (and no, it's not an abbreviation). ISO is the level of sensitivity at which your sensor can handle light. In human terms, how sensitive is your retina to your surroundings. In the sake of good fun and horrible mentorship to beginning photographers, go out to a bar tonight. Have yourself somewhere between 3 to 5 Blue Motorcycles and pick back up right here in the morning.
--------------------------------------------------- If you can read this, but the preceding line isn't sitting still, we can continue. Welcome back!
Hey, there friend! How's that hangover? So, you notice how you're head hurts when you're around a lot of brightness? That's the best way I can give you a real life way to figure out what ISO is. On your camera, I'll keep it really simple--lower ISO = darker, clearer image; higher ISO = brighter, grainier image. That's about it, now go eat a banana so I can wrap this up and feel better about getting you drunk.
Now that you have a general understanding of exposure, you have the tools to create a perfectly exposed shot. If you're capturing moving targets and you want them to look frozen: use a fast shutter speed, low f-stop, and a higher ISO. The best way to get a handle on it all is to grab a camera and go experiment. There's only so much you can learn without practice.......or hangovers.