Understanding Sensitivity

One of the marvels of digital photography is the ability to adjust your film speed from shot to shot without replacing a major component inside the camera.   With a flick of a couple buttons, you can immediately change the speed of your camera’s sensor.  That control gives incredible flexibility to adjust to varying light and desired results.

Film speed is the measurement of how sensitive the camera sensor is to light.  For those who remember, this measurement is still recorded as ISO.  To put ISO in its simplest terms, the higher your ISO number the more sensitive your camera will be to light.  Many point and shoot cameras have an ISO range from 100-800.  Higher end point and shoot’s often up that range to 1600.  DSLR’s go even higher, with some of the newer ones able to go as high as 12,800.  Here’s how those numbers work.  Every time your ISO number doubles, your camera’s light sensitivity doubles.  The jump from ISO 100 to ISO 200 means your camera will record twice as much light in the same amount of time.  The same is true for the jump from ISO 200 to ISO 400.  That means when dropping from ISO 400 to ISO 200 the camera is half as sensitive to light.  Every change of the ISO, increases or decreases the camera’s sensitivity to light.  Unlike shutter and aperture settings, ISO impacts light from ambient and flash equally.

The adjustment of ISO has a greater impact on your photography than merely increasing light.  The adjustment of overall sensitivity to light allows the photographer more latitude with the shutter speed and aperture.  Increasing the ISO helps the shooter be able to take pictures in lower light.  In certain settings, bumping up the ISO can allow the photographer to shoot with only the ambient light.  In other settings, the ISO can help increase the effectiveness of the flash.  When shooting sports, a higher ISO can mean the difference between a blurry or sharp image.

Higher ISO comes with some cost.  The higher the ISO the more noise will be introduced into the image.  The amount of noise introduced will vary from camera to camera.  For example, I have one camera that I refuse to shot at higher than ISO 200 because the amount of noise degrades the picture quality too much.  With another camera I will shoot all the way up to ISO 800 and still have acceptable picture quality.   Higher ISO will also have a tendency to mute the colors, so if you are looking for vibrant, eye popping saturations, keep the ISO as low as possible.

ISO is an easy calculation and simple to use.  Make the most of it.  Some quick tips when adjusting the ISO:

  • Keep the ISO as low as possible to get your shot with a minimal amount of digital noise.
  • Don’t allow ISO to be your only solution to low light.
  • Use the ISO to help balance ambient light and the flash.
  • Don’t forget the other sides of the exposure triangle

%d bloggers like this: