Yesterday’s Topic: Photography Jargon
Do you remember Shutter Speed from the Exposure Triangle?
Shutter Speed affects blur. Get that into your noggin right now.
It does some other things, of course, but the biggest effect it has on the average photo is stopping motion, or not stopping motion, depending on how it is used. Motion can be in front of the camera or the camera itself moving. Of course, blur will occur if things aren’t in focus, but let’s assume all is in focus.
Shutter Speed is the speed at which the shutter inside your DSLR (not Point and Shoots, as they use as scan of the sensor instead, which functions the same, essentially) opens and closes to let in light. That amount of time is expressed as, well, time. 1″ is one second open shutter. 5″ is five seconds open shutter. 1/60 is one sixtieth of a second open shutter. I know some of you out there hate math, but it will come into play. Here’s one example. Which let’s in more light, 1/10 or 1/100?
Answer: 1/10. Remember: Larger denominator (that number on the bottom of the 1/ fraction) = less light = faster shutter speed. 1/10 lets in more light that 1/100 than 1/1000. There’s a diagram at the bottom to help with this memorization.
I know that is over simple for those that enjoyed or at least ‘got’ math, but I have taught this enough to know many out there outright hate math.
So where the heck is this shutter and just how does it work? Let’s look at, what can be loosely called, a diagram of a camera:
When the camera shutter is not pressed, this is how a camera sits. Light comes in through the lens, is focused, passes through the aperture, bounces off the mirror, bounces twice off the pentaprism and then through the eyepiece so you can see it. Do you notice the shutter is in a bunch of pieces? This is to represent the two curtains of the shutter; front and back. I used four pieces but yours might have more or less. Here’s a picture looking in through the front of my camera for the curious.
That bright thing at the top is my thumb holding the mirror up and out of the way. What you are looking at is the front curtain of the shutter. Notice the individual blades (four of them). Behind this curtain is an identical curtain. When you press the shutter release all hell breaks loose. The mirror flips up out of the way (without the aid of my thumb). While it is doing that, the shutter curtains performs a little dance that looks like this:
That’s how the shutter functions. When things get going really fast, the second curtain follows the first curtain, only letting in a smidge of light to expose the sensor for the set time, such as 1/200th of a second. Like so:
The faster the shutter speed, the more action in front of the camera is stopped. The slower the shutter speed, the more things in front of the camera can blur. To break blur down a bit further, let’s think about how you see things.
You see things because light bounces off of them and hits your eye (please don’t make me draw an eye…..you won’t like it, but it is a lot like a camera). You aren’t seeing the bunny, per se, you are seeing the light bouncing off of it. This plays into White Balance, covered later. A movie projector shows individual frames on a screen, one after the other, at 24 frames per second (more or less). What happens when two or three of those frames are shown on the screen at the same time and there is slight movement between them? The image isn’t crisp like it is when just one image is shown at a time. This is essentially what blur is.
Blur is represented in the camera when light bounces off of an object and, because of a slow shutter speed where light is allowed to hit the sensor for (relatively) long periods of time, hits the sensor in two spots or more. (Again, I’m only talking about movement blur, not out-of-focus blur.) If that shutter is left open for, say, a second as in the first shutter diagram, the bunny can move a fair amount and light will bounce off of it and hit different parts of the sensor. Multiple images so close that sharp edges look blurred.
Now this isn’t necessarily bad. It can be used for some cool effects and we’ll cover Pan Blur, Light Trails and long exposures with flash later on in the month.
Moving objects need a faster shutter speed (1/1000 is faster than 1/60 is faster than 1″) to be able to make them appear sharp and not blurred. This is also true of you, the camera holder, moving. If you aren’t still and move the camera while shooting and the shutter speed is slow, say 1/10, then things will blur. We’ll go over How To Hold A Camera later as well.
An important thing to know about shutter speed is it is linear in the amount of light hitting the sensor. Meaning 1″ is twice as fast as 2″. 1 is half of 2. 1″ lets in half as much light as 2″. 1/2″ lets in half as much light as 1″. 1/4″ lets in half as much light as 1/2″. 1/8″ lets in half as much light as 1/4″. 1/15 (there is some rounding in cameras these days) lets in half as much light as 1/8″. 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000 to the highest most cameras will go of 1/8000. Each of these halving of light (or doubling of light if you go the other way on the scale) is called a stop. A stop is a very important concept and it will come up again and again.
In this case, going from 1″ to 1/4″ is two stops less light. That is, 1″ to 1/2″ was half as much light (1 stop) and 1/2″ to 1/4″ was half again as much (1 stop) = 2 stops. Those good with math can just divide or multiply the fractions by 2 for each stop of light.
Pop Quiz: How many stops less light is there between 1/60 and 1/1000? I’ll reveal the answer tomorrow.
Now then, before I wrap this up, here’s a piece of a puzzle which will be revealed this week. It’s meant as a quick reference and helps some people remember their shutter speeds and what they do. The arrow represents more light hitting the sensor down to less light hitting the sensor. If you want to take pictures of slugs, you can get by with slower shutter speeds. If you want to take pictures of bunnies on scooters, you’ll need faster shutter speeds. The word Blurry is to indicate if you are hand holding a camera, or if there is movement in front of the camera, it is likely to be blurrier at the top of the scale. Of course, this scale extends past both 1″ and 1/250
As always, fire away with the questions!
Next Up: Aperture explained
31 Days To Better Photography is a series written by professional photographer Peter West Carey on The Carey Adventures.Com. The series is designed to unravel the mysteries of photography so you can take better pictures. Subscribe here to receive all the updates and bonus material. Your comments are always welcome.