Is Snow Blue?

Exposure Compensation

When full automatic fails you!

If you took any photographs of the recent snowfall I bet the snow appears blue or grey if you left your cameral on a fully automatic setting, as in the image on the left above.  

That is because your camera does not know what the scene in front of it looks like, it does not know whether you are photographing a snow field in full sunlight, a courtyard in the dark, or a landscape in the day.  It does not know how bright the scene should look so it makes a guess and exposes it to make it an average grey (because that is what most scenes are).  So your snowfield looks dull and grey, the courtyard is too bright, and the landscape is, hopefully, as expected.

Experiment

The following experiment demonstrates this.  I have taken 2 photographs using the fully automatic programme setting on my Canon DSLR.  (I had to hunt to find it).  The 2 photographs were of a black card and shiny white perspex zoomed in to fill the image.

Black card

White perspex

The white image appears 95% grey, the black image a bit darker (with dust marks) but still not true black.

Repeating the experiment using manual settings to under/over expose by 2 stops produced the expected black and white results.

Black card - 2 stop

Clearly not the most interesting photographs I have ever taken this experiment demonstrates how the camera has made a mistake and has under/over exposed the 2 images by 2 stops.  Therefore to correctly expose the picture of the croquet lawn above I had to tell the camera to over expose the scene by 2 stops.

This is one of the most useful controls on your camera once you start to take control of your camera.   My camera has several ways to set exposure compensation either manually (my preference) or using on screen guides.  

White perspex + 2stops

One word of caution, always cancel exposure compensation after any shoot as it is so easy to forget and then continue to apply it in error next time you take your camera out.

You need to search online or look at your camera manual to see how to to set exposure compensation on your particular camera, including mobile phones.