The second part of the Exposure combination is Shutter Speed. The shutter stays closed until you decide to mash the button. It opens for a fraction of a second (usually) to let the light hit the film or sensor and capture that magic moment in time.



If you remember from yesterday, the Aperture controls how much light comes through the lens. The Shutter controls how long that light hits the film or sensor. Proper exposure = just the right combination of the two. As you might imagine, there are a number of combinations of Aperture and Shutter Speed that result in proper exposure.



Shutter Speeds are expressed as fractions of a second. When you see 15 or 60 or 250 in your viewfinder it’s really 1/15th, 1/60th or 1/250th of a second. Exposure times of one second or more are normally indicated by the letter ‘S’ next to the number. 1s, 2s, 4s would indicate one, two or four full seconds.



Just as with Apertures, each step up and down the scale of shutter speeds will halve or double the amount of light. Shutter speeds are as follows:

1s, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000 and so on.



How do Shutter Speeds affect how your pictures look? They control how action and movement are recorded. Fast shutter Speeds (1/250, 1/500, 1/1000) will stop action. A golf swing, a tennis racket or baseball bat, a race car, or any other sport are times for using high Shutter Speeds. On the other hand, slow Shutter Speeds will blur movement. The most common use is for waterfalls and flowing water to get that smooth, milky look to the water.



Tomorrow I’ll start discussing how Aperture and Shutter Speed work together. Then we can jump into Exposure Modes and how you can best use them to achieve great pictures.