Camera Settings 103: Identifying ISO
What is ISO in Photography?
ISO controls the amount of light a camera requires. Increasing the camera ISO setting will decrease the amount of light the camera needs in order to capture the image. Put simply, ISO is a camera setting that will brighten or darken the photo. Choosing the correct ISO is dependent on the available ambient lighting, as well as any movement in the scene. Low ISO settings can maintain image quality better than higher ISO settings, but may not be the best choice for freezing motion.
How to Adjust Camera ISO?
Adjusting your ISO can be accomplished in several ways, and most digital cameras have a similar setup. Lower ISO settings create the need for longer exposure times. Higher ISO settings allow more light and can decrease the exposure time needed. Setting an ISO stop allows you to maintain a certain image quality, while making the required adjustments with shutter speed and aperture. Most cameras allow ISO stops at different ranges (200 - 1600) or (200 - 3200), and can assist in controlling the light the camera requires.
Auto Mode:
The camera will automatically meter the scene and determine the best ISO setting to maintain the image quality.
ISO Priority Mode:
This allows you to manually adjust the ISO setting, while the camera automatically calculates the appropriate aperture and shutter speed.
Manual Mode:
Allows for full control over all camera settings. The camera will NOT adjust for any environmental or lighting change.
How Does Digital ISO Work?
Camera ISO works similar to recording sounds with a microphone. When capturing low volume sound, the microphone’s sensitivity may be turned up, but so will any ambient noise. Likewise, increasing a camera’s ISO will expose light artifacts in your image known as noise or grain. This causes a reduction in the image color accuracy and dynamic range; reducing the post-editing flexibility of the image.
Pro-Tip: Doubling ISO will effectively half the shutter speed, and is useful for freezing motion in low-light conditions (800 → 1600 ISO = 1/250 → 1/500 Shutter Speed).
Helpful: Full-Frame sensors are better equipped for low-light conditions, and can have a larger photosite to megapixel ratio.
What is Base ISO?
Base ISO is the lowest ISO value set by the camera manufacturer, and is determined by the camera’s photosites. (Photosites are the image sensors behind the shutter curtain. The photosites capture photons during the exposure period and translate this into a digital image). Typical base ISO numbers range from 100 to 200 for most manufacturers. The lower the ISO value, the more environmental light the camera requires.
Pro-Tip: Adjusting aperture to decrease the depth-of-field (opening up or reducing) can aid in managing lower ISO settings.
So What ISO Should You Use?
Choosing the ideal ISO depends largely on environmental factors. Good lighting conditions, along with little to no movement, can utilize lower ISO settings - especially mounted on a tripod. However, having plenty of ambient light can still require a higher ISO setting if the subject is moving too fast to freeze the action, or when shooting hand-held. By assessing the environment, and adjusting the shutter speed and aperture, the ISO setting can remain as close to Base ISO as possible - maintaining image quality.
Low ISO Setting = Base - 800 = Outdoor Photography - Landscape, Architecture, Still-Life
Mid ISO Setting = 800 - 3200 = Indoor Photography - Lifestyle, Wildlife, General Purpose
High ISO Setting = 3200 - 6400 or higher = Night Photography - Moon, Stars, Night-Life
I personally shoot in Aperture Priority mode most of the time, and AP mode automatically selects the best ISO for the scene. It may be helpful to set up an ISO stop on your camera to prevent higher ISO values from being automatically selected. I recommend taking photos of the same scene and adjusting your ISO to see the effects it has, and to capture a different style of photography. The greatest way to figure it out, is to simply take more photos and play with the settings (be sure to use a tripod in order to eliminate any camera vibration).
