Monday, March 21, 2011

The Basics of Exposure

Happy Monday, everyone! Sula here, with a little insight into digital photography.

Before I start, I have to admit that I'm no pro as far as photography is concerned. But throughout the years, I've taken tons of pictures and done some reading here and there, so with all the trial and error, I learned a thing or two!

Today, I'd like to go really basic, though, and talk about exposure. As I just mentioned, I've been taking pictures for years, but to actually grasp the concept of exposure, it seems like it's taken years for me. But there are actually really simple ways to understand what's going on. In a nutshell, "exposure" means the light that enters and interacts with the camera. There are three basic elements that contribute to a picture's exposure:

1. ISO (measure of sensitivity to light)
2. Aperture (size of lens opening at the time a photo is taken)
3. Shutter speed (length of time the shutter of the camera is open)

Now, these three areas are huge aspects in themselves in photography, and we could write entire books about every single one of them. But as I promised - I want to keep things really simple today. I'll use an example I came across the other day that explains fairly well the role these three elements of exposure play in photography. Some people compare the processes by using the illustration of a window.


According to Darren Rowse (Digital School of Photography) your camera is ...

"... like a window with shutters that open and close.

Aperture is the size of the window. If it’s bigger more light gets through and the room is brighter.

Shutter Speed is the amount of time that the shutters of the window are open. The longer you leave them open, the more light comes in."

ISO - according to Rowse - works like a pair of sunglasses you put on to manipulate the amount of light your eyes are exposed to. It works similar with the camera. The lower the ISO, the lower the sensitivity to light. In other words, a photo taken at ISO 100 will turn out darker than a photo taken at ISO 1600. This means that you will have to adjust the ISO depending on the light conditions you are taking pictures in. If it's a bright, sunny day, to choose an ISO of 100 or 200 will work just fine. The darker your shooting environment is, the higher you have to go with the ISO. That, however, will have an affect on how grainy your photos turn out. The higher your ISO the grainier the image gets. (See the very grainy image below that was taken in a high ISO mode.)


So, the alternative to high ISO is to choose a lower ISO and use a tripod to steady your camera. If you choose a low ISO in poor lighting conditions, chances are your picture will turn out blurry without a tripod.

Also, to use low ISO in a low-light environment means you have to keep your subject very still in order to get a clear shot. Depending on your shooting conditions (and how much influence on the scene you have), it's your call to decide how high or low you set the ISO.

The same is true for aperture and shutter speed. All three of them have an affect on your image exposure, and all three will affect each other.

You can increase the aperture, which is like choosing a bigger window - more light can come in (important for low-light conditions).

You can change the shutter speed as well. Increasing the shutter speed, means there is less time for the light to come in, which will result in a darker image (necessary in bright daylight conditions). Decreasing the shutter speed, means you allow the picture to receive more light (useful in low-light conditions), but it also means your photos can get blurry more easily, the lower your shutter speed is.

If you have a camera that allows you to use manual mode, try playing around with these different aspects of exposure. Knowing how to use them well, can spare you not only a lot of blurry or over-/under-exposed photos, they can also help you avoid the use of a flash-light, which usually causes harsh shadows and lighting of your pictures.

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