by Kathleen Reeder
Getting a good exposure in snowy conditions can be a little tricky. Does the snow look gray in your photos? This tip explains why this happens and what to do about it.
Camera meters are designed to give exposure readings perceptually in the middle between white and black, a middle-tone value. When your scene is mostly snow, the camera meter gives a reading that brings the tonality back to neutral gray, which causes the image to be underexposed. In other words, your camera thinks that a correct exposure is to make the snow gray!
Exposure Compensation is the +/- button on your camera and is used to modify the shutter speed and/or lens aperture setting from what the camera’s meter has determined as a correct exposure. To retain the snow’s whiteness, you want the camera to allow more light on to the sensor. Increasing exposure by one stop (+1.0) to two stop (+2.0) is typically what is needed.
When shooting in Shutter Speed Priority, the camera will adjust aperture by the compensation amount after it has metered the scene. For example, let’s say at a shutter speed of 1/500s, the camera meter determines f/8 to be the correct exposure. With an exposure compensation setting of +1.0, your camera will change the aperture from f/8 to f/5.6, effectively doubly the amount of light reaching the sensor.
When shooting in Aperture Priority, the camera will adjust shutter speed by the compensation amount after it has metered the scene. Let’s assume at an aperture setting of f/5.6, the camera meter determines 1/250s to be the correct exposure. An exposure compensation of +1.0 will cause the shutter speed to be changed from 1/250s to 1/125s, again effectively doubly the amount of light reaching the sensor.
The histogram is the best tool for determining the amount of exposure compensation needed. Take a photo of the scene and check the histogram. In snowy conditions, a good histogram will be pushed towards the right and ideally drop to zero before reaching the edge of the graph to retain a little detail in the snow. The example histogram below corresponds to the photograph above. As you add more “+” exposure compensation, the histogram will move further to the right.