July 20, 2011
Mastering sensitivity is not a call to embrace your feminine side, rather to learn about one of the most powerful capabilities of your camera: variable ISOs.
Sensitivity is essentially a measure of the amount of light needed to make a correct exposure. The greater the sensitivity of your camera, the less light is needed. This is measured in ISO and the higher the number, the greater the sensitivity. It might sound very technical, but in practice it gives you greater freedom to take better pictures and to experiment with settings.
Most cameras start at a base sensitivity of around ISO 200. Every time you double the ISO you need half the amount of light. In photographic terms this is called a stop, and is the same as a whole click of apertureor a doubling or halving of the shutter-speed. So increasing the ISO from 200 to 800 could make the difference between a potentially shaky 1/15 of a second and 1/60.
The main reason for increasing sensitivity is to be able to use a faster shutter-speed. This can avoid camera shake, allowing you to take pictures in situations where you would otherwise need a flash or a tripod. The faster speed can also prevent fast moving subjects from blurring in your picture.
Increasing the sensitivity will let you use a smaller aperture: giving more depth of field, so more of the subject in front of you will be in focus. This can be perfect when photographing interiors, or even landscapes in poor light.
As with car manufacturers and speedometers, camera manufacturers often put wildly inflated maximum ISO capabilities on their cameras. Although on paper they are capable of certain sensitivities, in practical terms the quality implications often render them unusable. The main drawback is noise: random speckling and stray coloured pixels that can spoil an image. Ugly and distracting, it can obscure detail.
With early digital cameras this used to be a much greater problem, even at relatively low ISOs. Modern cameras though have much better high ISO capabilities. Bear in mind that the size of the sensor also has an effect. The smaller the sensor, the greater the noise at a given sensitivity.
Higher sensitivities are also not as good at handling contrast, and in general, while you should raise the ISO whenever you need to, it’s also is best to keep it as low as is practical.
It is also worth experimenting with your camera to find the maximum ISO that you’re happy with. This will vary by camera, by subject and even by your own personal preferences.
Many cameras have an auto setting that will raise or lower the ISO within set parameters. This can be a useful feature in lower light levels, but can take away creativity and control when you want to use a slower speed for blur or for creative reasons. My preference is to leave this switched off, and make changes myself, but if you don’t want to delve into your camera settings then Auto ISO might help you to get better images.
All photos by Steve Davey. Header image: Monastery interior, Ladakh, India taken at ISO 1600.
Steve Davey has an exclusive range of Travel Photography Tours. For more information go to www.bettertravelphotography.com/phototours