Digital camera ISO speed is the setting that corresponds with the film speed used in traditional film based photography. Digital cameras with the greatest number of ISO options are highly prized by both amateur and professional photographers, since these cameras have the greatest amount of flexibility when shooting in bright and low light situations.
About ISO
ISO is an abbreviation which stands for the International Standards Organization. This organization created the system used for rating the sensitivity of film based on an algorithm. What does this mean for your digital camera? Simply put, when the ISO number of a digital camera's sensor doubles through a change of settings, the sensor has become twice as sensitive to light as it was before.
Digital camera ISO speed is important to both professional and amateur photographers alike. By changing how sensitive the digital sensor is to light, the ISO determines how much light is necessary for the correct exposure of an image. This means that photographers working in a low light situation that have access to high ISO speeds can take images with less available light. This useful in situations where flash is inappropriate, such as a church wedding, or when it is impractical, such as at a sporting event or open air venue.
ISO Numbers
Lower ISO numbers mean that the sensor is less sensitive to light. This allows the photographer to use a longer shutter speed or wider aperture to gain the correct exposure in a very bright situation, such as shooting in a well lit studio or on a bright, sunny day. As the ISO number increases, the sensor becomes more sensitive to light. Very high ISO numbers allow the photographer to use less available light for a correct exposure, but can affect the quality of the final image through digital noise and grain.
When To Use a Low ISO
Low ISO numbers are useful in many situations. The most obvious would be a brightly lit area, such as outdoors in direct sunlight or while using very bright studio lighting. However, these are not the only situations where a low ISO comes in handy. Lower ISO settings tend to produce clearer photographs, so a photographer may opt to select a lower ISO setting and compensate for the reduced sensitivity by adding flash, lengthening the shutter speed or opening the aperture wider.
When To Use A High ISO
High ISO settings make the sensor more sensitive to light, so it stands to reason that when the available light is low, a high ISO setting will help the photographer compensate for the lack of light. This is especially useful when a fast shutter speed or narrow aperture is also necessary, since these will cut down on the amount of available light striking the sensor. When raising the digital camera ISO speed, its important to remember that while you may be adding sensitivity, you're also increasing the chances of digital noise and color fringing affecting your image.
Digital Camera ISO Speed
One of the drawbacks of using high ISO speeds is the high incidences of grain and digital noise. High ISO settings often cause grain to be added to photos. Digital noise manifests itself as grain or multicolored dots on areas of the image and can be a problem, as it is difficult to correct. However, if you are prepared for this, it can be quite an artistic asset. Camera manufacturers such as Nikon and Canon have addressed the subject of digital noise at high digital camera ISO speeds, creating camera bodies containing sensors less likely to experience this phenomenon. Noise can be corrected in the editing process using programs like Adobe Photoshop, Neat Image and Noise Ninja.
