ISO Sensitivity is a standard set by the International Organization for Standardization (ISO) that represents sensitivity to light as a numerical value.
A higher number indicates a higher sensitivity and a greater ability to capture light. The ISO Sensitivity is set and changed in the shooting settings menu.
If the ISO Sensitivity is doubled, the amount of light reaching the image sensor required for a suitable exposure is halved. For example, if the ISO Sensitivity is increased by one stop from ISO 100 to ISO 200, you can shoot with the shutter speed one stop faster or with the aperture value one stop narrower. This is useful for increasing the shutter speed to freeze subjects in motion or to deepen the depth of field (that is, the range that appears to be in focus) by narrowing the aperture. In dimly lit conditions, such as when shooting indoors, it is easier for the shutter speed to become slow, which can be a cause of camera shake or subject blurring. In those situations, you can make the shutter speed faster by increasing the ISO Sensitivity, which will minimize such blurring. In cases where you want to deepen the depth of field by narrowing the aperture or freeze a moving subject by increasing the shutter speed, if the amount of light available is not enough to do so with just the combination of the aperture and the shutter speed, increase the ISO Sensitivity.
Although the amount varies depending on the camera, when the ISO Sensitivity is increased, white or colored dots known as noise can make the image seem grainy.
Noise that becomes more noticeable as the ISO Sensitivity is increased can be reduced with the noise reduction function. You can select the amount of noise to be reduced. Depending on the setting, the amount of time it takes to record images may get longer.
* When set to AUTO, the appropriate amount of noise reduction will be automatically applied to images when they are taken.
In dark locations, you can increase the shutter speed to make camera shake and subject blurring less likely to occur. In bright locations, you can reduce the ISO Sensitivity to make the amount of noise smaller. ISO AUTO is a setting in which the camera will automatically make these settings depending on the shooting conditions.
If you do not want the ISO Sensitivity to change, be sure to set it to a setting other than AUTO.
When the ISO Sensitivity is set to AUTO, the upper limit the camera can automatically set the ISO Sensitivity to can be set in the shooting settings menu under [Maximum ISO for ISO Auto]. With this setting, the value for the ISO Sensitivity will fluctuate between ISO 100, which is the lowest value used in most cameras, and the value set in the [Maximum ISO for ISO Auto] setting, thereby preventing the ISO Sensitivity from increasing too much.
* The notation and way of setting these values varies depending on the model used.
Set the values that you think will enable you to shoot with no problems in terms of image quality. Naturally, the value for the ISO Sensitivity will increase as far as the upper limit set in dark scenes, but normally the lowest value possible will be selected. If the value for the [Maximum ISO for ISO Auto] is low, the image quality will be better, but it will also be easier for camera shake or subject blurring to occur in dark scenes.
