Thursday, 18 April 2013 12:21

SPEED FREEZE Part 4

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We have all seen those lovely shots where every droplet of water is perfectly frozen in an action shot - in this issue we show you how to do it, even with your compact camera. But first let’s have a look at how the camera achieves this, because when you understanding how it’s done you can manipulate your camera settings to achieve the result you desire.

The lens focuses the image onto the sensor. The shutter, whether it is mechanical or electronic, then exposes the image on the sensor. The time that the image is exposed is the shutter time. Beware - if there is any movement while the image is being exposed it will show up as a blur. This blur can be caused in two ways - when the subject moves or when you move the camera. Never underestimate the impact of movement as it is introduced very easily. Good photographers develop a stance and shutter release sequence so that they can hold the camera still and so minimize movement. As you zoom in you automatically increase the potential for movement, hence the reason why I suggest rather walking closer to the subject.

Shutter speed is your defense against movement! The faster the shutter speed the less time the image is exposed to the sensor and the less potential for the image to move during the exposed time. So when you zoom in remember to increase your shutter speed to counter movement.

Now let us look at how you freeze the action in that water droplet shot.

To expose correctly you need the right amount of light, and by reducing the shutter speed (namely making it faster) you are effectively reducing the amount of light hitting the sensor. On your camera you will see “Tv” and “Av”. The Tv is the time interval or shutter speed, and in semi-manual mode you can specify the Tv. Set the Tv to 1000, or 1/1000 of a second, that’s how long the exposure will be. Frame the shot and look at the light meter reading and f-stop. The light meter will show you if you have enough light and what f-stop the camera will automatically select. If you need more light you can do the following:

  • Increase the exposure to 500 or 1/500 of a second. Remember you are now reducing the freezing ability of the shot.
  • Wait for more sunlight or reflect sunlight onto the subject
  • Increase the sensitivity “ISO” but be prepared to have a grainier shot as a result
  • Reduce the zoom as most lenses will allow more light at wider settings

Let’s take a pebble hitting the water. Your camera is set up for 1/1000 sec at f2.8 and ISO200. With this setting you can expect good freezing ability and an ISO 200 gives good image quality. The f2.8 will give a shallow depth of field which means you have to pre-focus carefully on the subject.  The background will be out of focus, which normally is desirable in many compositions. Now it’s all up to you to capture the moment when the pebble hits the water.

Another good use of fast shutter speeds is when you need to use the longer zoom. The fast shutter speed reduces the camera shake that is an increasing factor the longer the lens is. It sounds simple but here is the catch - normally the longer the lens the less light it passes, and with less light you need longer shutter speeds. To overcome this you need expensive “big glass” that will allow lots of light through it. To achieve this, the lenses normally have large glass surface areas. Sports and photojournalists love the 70 to 200mm f2.8 lens with the emphasis on the f2.8. If you are stuck with a 200mm f5.6 lens that allows you a shutter speed of only 1/125, just mount it on a tripod and look at the quality difference in your images. If you do not have a tripod at hand look for a suitable sturdy object to stabilise your shot. This could be a fence post, table or branch. Inside the car use the door window but switch off the car to remove the engine vibration. A good idea is to use a sandbag to rest the camera on.

One last thing - it is not always desirable to stop all the action and sometimes the blur on parts of the object actually assists in the composition of shots. For example an aircraft in the air with a perfectly stopped prop just does not look natural, unless the occupants have a terrified look on their faces giving significance to the stopped prop!

Read 887 times Last modified on Wednesday, 22 May 2013 10:32

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