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Exposure 101: Shutter speed

Photography’s a funny thing…  With most arts and crafts you start with a nothing apart from say paper and paint or a bucket of clay and fashion something of beauty from that.  Photography works the other way around:  we start with a fully formed scene in front of us and attempt to manipulate it in some way to capture an impression of some part of it we’d like to convey to our viewer. Luckily we have a few tools to help us do that and one of them is shutter speed, that aspect we’ve already mentioned in connection with exposure. So, what is it? Well, let’s go back to film for a moment.  We load a roll of light sensitive material in the back of our cameras which is contained and maintained in a light-proof environment. Then, for a fraction of  second, we expose it to light, move the film on and repeat before sending it off to be made into prints. The shutter is the device that controls for how long the film is exposed to light.  It might be a blade within the lens or it might be a pair of metal or fabric curtains just in front of the film itself. With digital cameras both of those options still exist but now it might be just an electronic virtual “shutter”, not a physical one at all. The actual mechanism is not so important for right now. It’s just something that allows us to control for how long the sensor is exposed. So how can we use this to change our image? Let’s think of photographing a race car at full speed. What are some options?

  • Short shutter speed, let’s say 1/2000 second
  • Long shutter speed, maybe 1 second
  • Something in the middle

Let’s think about how these might come out.

  • The short shutter speed will freeze all motion leaving the card looking the car looking nice and sharp, but as though is was parked there, not giving any sense of the speed at which it was travelling. That might be ok if we want to see the driver’s face, but as it’s a race car, maybe we’d like some impression of speed instead?
  • So let’s try a long shutter speed. Well with the shutter open for a second all we’ll capture will be a featureless blur. Again, that too might be ok for some uses: an abstract impression of movement perhaps.
  • So how about something in the middle?  This where it gets interesting. By varying the shutter speed we can vary the amount of blur and so choose how much detail we want and how much blur we want to indicate speed!

So how do we do that?

shutter priority mode Tv Exposure 101: Shutter speed On your camera choose shutter priority mode. On most cameras with is probably sensibly labelled “S” but on some Canon cameras will be called ”TV” (time value). The camera will still calculate what it thinks the correct exposure is, but now lets us dictate what shutter speed to use.

So now we’re in control let’s go out and shoot.  Rather than a car we’ve chosen an example of running water here. The first is a perfectly reasonable shot, at 1/250 second.  But, to me, it’s a bit boring.  There’s no feeling of movement, we could just as well be looking at ice: 7d 12678 2012apr27 1559 jpg 1kp scr cr frb Exposure 101: Shutter speed

So let’s increase the exposure by quite a bit, to 1/13 second. Here the impression is totally different!  We feel the water’s speed and now can see the warm afternoon sun playing off of it.  And the blurred water forms a nice backdrop to any foreground elements in the picture rather than fighting with them: 7d 12684 2012apr27 1600 jpg 1kp scr cr frb Exposure 101: Shutter speed

And,here’s a fountain at 2 seconds: 30d 24070 2010nov23 1050 jpg 1kp scr cr frb Exposure 101: Shutter speed

Next up, aperture…

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