When to Opt for High Dynamic Range on Digital Cameras
High dynamic range refers to how much variation in light your image can handle before it becomes underexposed or overexposed. On a digital camera, this is dependent upon two factors: the aperture and the ISO.
ISO is the digital camera equivalent of film speed. The higher the ISO, the less light is needed to expose the image, at a sacrifice of quality. The aperture controls how much light passes through the lens when the image is exposed. An open aperture lets in more light through the lens and thus allows you to expose an image in a low light situation.
When Do You Shoot in High Dynamic Range?
You would want high dynamic range on the camera when you have images with large variations of light that you can not control. High dynamic range keeps the exposures balanced instead of having parts of the frame blown out from being too bright or dark and grainy. High dynamic range also means that you have more control over the aperture which affects your depth of field. Overall, it allows you to not need to fight your exposure and frees you up to concentrate on other aspects of photographing your image.
You would want to opt for low dynamic range when you're trying to get overexposure or underexposure to work for you as an artistic effect.