So last week we tackled one leg of the “exposure triangle”: Aperture (if you missed it, trust me you will want to read it). This week we will cover shutter speed. While aperture is the amount that the shutter opens up, shutter speed is how much TIME that shutter stays open and therefore how long your camera’s sensor (or, in the old days, the film) is exposed. Although it’s usually displayed as a whole number on your camera (“250”) it is actually a fraction of a second, so that 250 is really 1/250th of a second. Ya, fast huh?
So what does this all mean? Why is it important? Well the faster your shutter speed (like 1/500), the less light is let in and the darker your photo may come out. Fast shutter speeds also freeze motion, so if you have kids that do NOT sit still (like I do) or kids playing sports, you’re going to want to use a faster shutter speed (1/250 and up is safe). That photo I posted for my 52 week challenge? I used a fast shutter speed to catch all of the tiny snowflakes flying out.
Ever take photos at night or in a dark room and found they were all blurry? Slower shutter speeds will result in blurry photos if you aren’t using a tripod or stabilizing your camera. Blur isn’t always bad though, sometimes you want to show motion, like a moving train or a flowing waterfall. However when doing this, you must always be mindful to brace your camera against something to prevent the actual camera from moving. 1/30 of a second may seem really fast to us but for your camera, it’s plenty of time to blur that photo.
The general rule is don’t go slower than the focal length of your lens without stabilizing it (for example, if you are shooting at 70mm, you shouldn’t go below 1/70 or it may be blurry). I bet those of you who read my aperture post are just thrilled right now that the numbers all make sense, higher number = faster speed. Woo hoo! So let me throw in a little twist, although I promise it makes sense this time 🙂 What happens when you slow down to ½ second? What from there? Well, you start the whole numbers, 1s, 1.3s, 1.6s, etc. While the fractions may be shown as whole numbers, whole numbers will have a “ after them, like 1”, 1.3”, 1.6”…
Are you guys still with me? We are almost there, I promise 🙂
So speaking of aperture, how does this all tie together? I’m going to try and make it as simple as possible. Whenever you increase your shutter speed a stop, say from 1/250 to 1/500, you are letting in half as much light. To keep the exposure the same you will need to adjust one of the other legs of the triangle (aperture or ISO) by a stop to compensate. I will save ISO for next week, so for this lesson you would want to increase your aperture (f/number) a stop, from say f/8 to f/5.6. Yes I said increase. Since you are shortening how LONG the shutter is open, you will need to make the opening LARGER so it lets in the same amount of light over that shorter period and your exposure will stay the same. So now to practice!
And I have great news- know how your camera has that “aperture-priority” mode to let you control that and let the camera do the rest? It also has a “shutter-priority” mode! Who knew? So all you have to do is switch it to “S” (Nikon) or “Tv” (Canon) and you can practice with different shutter speeds while your camera figures out the rest of the settings for you! See, who needs automatic mode? So get you camera out and practice on your fast moving subjects. Try a fast shutter speed during bath time to catch those splashes, or even drops from your kitchen faucet into a bowl of water. And then run that water and try out some slower shutter speeds to see how it makes that water flow look. Have fun, and please share!