Thursday 20 February 2014

Parameter #3 - Exposure

Maximum Score 15/100

See current scoring methodology HERE

Under-exposure is a deficit of light while over-exposure is a surplus.  If you are not already reasonably familiar with camera exposure and other photographic principals then I highly recommend a visit to CAMBRIDGEINCOLOUR.COM.  It is a superb online resource with lots of tutorials for everyone from the beginner to the expert photographer.

Achieving the perfect exposure is not easy, especially when trying to properly photograph a small moving subject in an environment with contrasting light and shade.  An image may appear reasonably well exposed overall but the bird in the image may not be well exposed.  The key yet again for this exercise is to focus on the bird and ignore everything else.

Each pixel on the camera sensor requires a minimal level of illumination to register the image. 
The greater the level of under-exposure the fewer pixels will have registered an image and the darker and flatter the end result.  Hence detail and colours suffer and identification becomes more difficult.  The overall effect is a darkened, flattened image.  Noise also becomes a factor.  Noise is the grey or multicoloured specks that serve to cloud and obscure detail and make photographs unattractive.

The other extreme is over-exposure.  In this instance the problem is one of too much light.  Colours and details appear burnt or bleached out from the image.  Individual pixels suffer from a surplus of light energy hitting them and there can even be a transfer or bleeding of energy between neighboring pixels.  The overall effect is initially a brighter, more contrasty and more saturated looking image, though extreme over-exposure manifests as a bright, flat image as all detail finally gets bleeched out.

Once again, we are not too interested in how an exposure was achieved, just the outcome.  I have tried to keep the scale reasonably clear.

  1. If an image is slightly over or under-exposed the effect will be only slightly obvious.  The likely affects on the image for ID purposes will be fairly minimal.  
  2. Moderate over or under-exposure is a significant enough problem.  Details start to become more difficult to judge accurately.  Colour is also affected and becomes more difficult to gauge.
  3. A majorly over or under-exposed image may be unusable.  However for those well practiced in and comfortable around image editing software it is often possible to extract a usable image from what might in the past have been considered a dead loss.  This is why I have not made extreme under or over-exposure a complete show-stopper.  I would however advise extreme caution around the use of image editing software.

No comments:

Post a Comment