Now that we have covered ISO, Aperture, and Shutter Speed we will examine how they work together for the proper exposure.
You can see by the illustration, if you increase or decrease one of the elements, one or both of the other elements much change to correct the exposure.
Let's say you want to shoot action sports. In order to freeze the action, a high shutter speed is needed. You determine that a shutter speed of 1/500 sec is needed but at ISO 100 and Aperture of f8 (sharpest aperture of your lens) the photo is very under exposed. Changing your aperture to f2.8 will allow more light into your camera and will brighten the exposure by 3 stops. This will also blur the background by changing your depth of field. When shooting action sports, having a sharp subject and a blurred background looks better in my opinion.
Now you decide that you want f8 for maximum sharpness and still need 1/500 sec for freezing the action. Increasing your ISO from 100 to 800 (3 stops) will allow a brighter exposure. This will however increase noise/grain in the photo but not enough to be an issue.
What about trying to add motion blur to your photo for water movement or streaking clouds. With your ISO at 100, aperture at f8, and a shutter speed of 1/20 sec is not slow enough to create water movement but the exposure is correct. Change the aperture to f22 (3 stops), now change your shutter speed by 3 stops to 1/2.5 sec.
Remember a STOP is a doubling or halving of the current number. Starting at 1/20, 1 stop is 1/10, then 1/5, then 1/2.5. Since cameras don't have a 1/2.5 sec using 1/3 of a second or 0.4 sec will be your options and will work just fine.
Now that you have a better understanding of how the 3 elements work together, get out shooting and adjust your settings to see how they affect the image and each other. If you have any questions, feel free to contact me with questions and I can help you understand the concept.
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