Back to Basics Photography: Exposure Control
In the upcoming months John J. Pacetti, CPP, AFP, will be writing a series of basic photography lessons. To find them all just search “Back to Basics” on our blog. This is the first article in this series.
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What is exposure control?
The better you expose and set up the image when you record it, the less work you have to do later when you process it. I would rather spend all that time in editing, in other ways. If I’m constantly editing because “I can fix it later,” I’m not using my valuable time to my advantage. If I capture the image properly in camera, I can spend that valuable time, with my family, on a hobby (oh, wait photography is my hobby). You get what I mean.
Exposure control is the use of shutter speed (SS), F-Stop (F-#), ISO to capture a properly exposed image. You are controlling the amount of light and length of time that light is hitting the sensor.
A quick explanation:
- Shutter Speed – Duration the shutter is open. The length of time the shutter is open allowing light to the sensor.
- F-Stop/Aperture – The opening in the lens. The size of the opening that light passes through to the sensor.
- ISO – The sensitivity of the sensor to light. Lower ISO for bright scenes, higher ISO for low or poor light scenes.
The below center images is an example of a good exposure. A good exposure can be achieved with any setting combination of ISO, F-Stop and Shutter Speed.
Under exposed 2 Stops:
Over exposed 2 Stops:
How it works:
ISO, F-Stop or Shutter Speed all interact with each other. You can’t change one without changing another and maintain the same exposure. That being said, assume you have set your proper exposure. You decide to make and adjustment in your F-Stop. You need to change either your SS or ISO (maybe both) in order to maintain the same good exposure. So, in order to maintain the same good exposure, If you change ISO; you need to change either F-Stop or SS. If you change SS; you need to change either F-Stop or ISO. If you change F-Stop; you need to change either SS or ISO.
To give you an idea of what I’m talking about, go get your camera, I’ll wait………………………… Now, look through your view finder. At the bottom of the view finder (at least in my Canon Cameras, that’s where it is) there is an exposure meter. Whatever your settings are, for this experiment, almost don’t matter. If you change your shutter speed, you’ll notice the pointer in the meter move left or right depending on if you increase or decrease your SS. The same thing will happen if you change your F-Stop. You are changing the exposure setting and can see that effect on the image exposure by the movement of the pointer on the exposure meter. This is a simple demonstration of course, but should give you some idea how exposure control can be effected for changes in any one of the the parts of the exposure triangle, SS, F-Stop and ISO.
I hope this gives you a general understand of ISO, F-Stop and Shutter. We’ll explore this more as our series continues.
John J. Pacetti, CPP, AFP – South Street Studios – www.southstreetstudios.com
2013 Instructor at MARS School- Photography 101, The Basics of Photography www.marschool.com
If you have question, feel free to contact me at [email protected] This email goes to my phone so am able to answer quickly. I’ll be glad to help in any way I can.