Wednesday, 20 August 2008

Shutter Speed

Background
Shutter speed determines the amount of light reaching the camera sensor and also influence how movement is captured.


Do you remember that earlier I said I was going to have a look at various camera functions and things in an effort to learn more about photography and my camera? Well I think I will start that now so that I have some homework for the weekend. I thought I'd look into shutter speed first. So now I just need to learn about how to use shutter speed to good effect and also how to set the various shutter speeds with my camera.

For the complete novices among us shutter speed is the amount of time that the shutter stays open. The amount of light reaching the sensor depends on the shutter speed. The amount of light reaching the sensor can also be controlled by other means such as aperture size. One of the reasons you might like to adjust the shutter speed is to capture or freeze movement.

For fast moving subjects such as sports photography then the shutter can be set shorter so that it freezes the motion. The drawback to this is that you might need to compensate for the lower amount of light reaching the sensor. You can do this by adjusting your cameras other functions such as aperture size etc. In poor light the shutter can be set to open for longer so that it lets in more light. The drawback of this is that the photos can be prone to blurring. You can reduce the risk of this by using a tripod and the self timer function on the camera to minimise disturbance to the camera. Soemtimes you may want to make the subject blurred such as when capturing head light blur. You can do this by having a slower shutter speed.

Shutter speeds are measured in seconds and have been agreed as -
1/1000 s
1/500 s
1/250 s
1/125 s
1/60 s
1/30 s
1/15 s
1/8 s
1/4 s
1/2 s
1 s

Using shutter speed to freeze motion
The shutter speeds that you need depends on the subject matter. A slow moving subject will need a slower shutter speed than a faster moving one. An approximate guide is -

Subject Shutter Speed
Walking 1/60 sec
Running 1/12 sec
Cycling, fast animals & sports 1/250 sec
Cars & motorsports 1/500 sec
Fast flowing water 1/500 sec

So how do you do this with your camera?
Generally speaking (I'll move onto the setting of my particular camera - the Canon Eos 450D - later) the best way of controlling the shutter speed is to use the shutter priority setting on your camera.....apparently.....I wouldn't know. This will automatically select an appropriate aperture to make sure the image is captured at the correct exposure. Sometimes with very fast shutter speeds not enough light reaches the image sensor - especially where light conditions are poor anyway. If this is the case you can try increasing the cameras ISO setting which increases the sensitivity of the image sensor.

How do I do it with the Canon Eos 450D?
Set the mode dial to TV to set the shutter-priority
Set the shutter speed
If the aperture displat starts blinking the ISO needs changing as the adjustable aperture range has been exceeded.

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