ISO Settings vs Light & Quality

Understanding ISO is important for both the professional and beginning photographer. Correctly adjusting ISO, shutter speed, and aperture, creates quality images virtually anywhere and anytime.

ISO in both film and digital cameras is a measure of the amount of sensitivity of the medium to light. In a film camera, ISO referrs to the sensitivity of the film, and in a digital camera, ISO refers to the sensitivity setting of the image sensor, simulating ISO in film. Film cameras require changing film with a different ISO if we wanted a different speed of film (more sensitive or less sensitive to light). Now, digital cameras allow us to change ISO on a settings menu with a turn of the dial. No change of film is required, and every image is saved on the memory card regardless of ISO setting.

Instead of film, digital cameras use image sensors. ISO (International Standards Organization) simply denotes how sensitive the image sensor is to the amount of light present. A higher level ISO, for example, means image sensors are more sensitive and pictures can be taken with less light. The other side of that equation reveals lower ISO settings are used when more light is available.

‘ISO Auto’ mode is available on most consumer digital cameras today. That means the camera will select a higher or lower ISO automatically, depending on light it senses. Amateurs are looking for cameras that are easy to use, and the auto mode is perfect for them. If they encounter a situation in which they just can’t get good light, they forego taking the shot. However the professional photographer has more options and he will need to learn to manually select ISO, adjust shutter speed and aperture settings, and then be able to take quality pictures almost anywhere.

With ‘ISO Auto’ off, the light meter on the camera tells you when you need more light, thus needing to change the ISO. You may have the choice of either using the flash mode or changing the ISO. Using flash may be the best choice for good exposure. On the other hand, if you are in a museum or facility that does not allow flash photography, using your knowledge to select a higher ISO setting means you still get the shot. Adjusting ISO will require an adjustment in shutter speed and aperture to compensate for the change in light coming in at any given time.

Lowering the ISO will lower the sensitivity of the image sensors and, with a scene that is already full of light, exposure is more likely to result in good quality. Again, depending upon what you want to capture in the photo (e.g., movement in a waterfall or waves on the beach), you may also need to adjust shutter speed and f-stop (aperture).

Our message in this discussion is that understanding ISO and developing the ability to adjust it depending upon the scene you’re shooting is another valuable tool in your camera bag. Appropriately adjusting ISO to circumstances of light equals good quality pictures.