We recently talked about aperture and shutter speed in photography, and now it's time to take a look at what is ISO in photography.
ISO (International Standards Organization) is one of the three pillars of the exposure triangle, the other two being shutter speed and aperture. Where shutter and aperture are the controls for adjusting how much light comes into the camera, ISO is the main governing body that regulates sensitivity ratings for camera sensors.
What is ISO in Photography
The ‘normal' range of ISO is around 200 to 1600, and with today's digital cameras you can sometimes go as low as 50 or as high as 204,800. The number chosen has two important qualities associated with it.
The first quality sets the amount of light needed for a good exposure. The lower the ISO number (100, 200, etc.), the more light will be required. The more light that's required, the more likely a slow shutter speed will have to be used. That means low ISOs, like 100 or 200, are most often used in bright situations (like sunlight) or when the camera is mounted on a tripod.
The other important quality tied to ISO is the amount of noise in the image. In film and digital cameras, raising the ISO means a decrease in quality, with an increase in what's called ‘noise.' Noise is the digital equivalent of grain, and results in a sort of “chunky” look to the image.
When to Use Low ISO
You should always try to stick to the lowest ISO (base ISO) of your camera, which is typically ISO 100 or 200, whenever possible, to retain the most detail and to have the highest image quality. A lower ISO will usually produce more color-accurate, aesthetically pleasing images, but there are certain situations where a higher ISO is desirable.
When to Increase ISO
You should increase the ISO when there is not enough light for the camera to be able to quickly capture an image. Anytime I shoot indoors without a flash, I set my ISO to a higher number (but still the lowest possible to achieve the shot I want) to be able to freeze motion. But before increasing the ISO, you should think if it is OK for you to introduce noise to the image.
Situations where you might need to push ISO to higher settings include:
- Indoor Sports Events where players are moving fast and there is limited light available
- Musical Concerts and Theatre shows which are performed in low light and often have ‘no-flash’ rules.
- Art Galleries, Churches, and Museums, because they have rules against using a flash and of course being indoors it is not well lit.
- Birthday Parties where blowing out the candles in a dark room can produce a nice moody shot which would be ruined by a bright flash.
Also, many photographers will raise their ISO to achieve a vintage aesthetic to their photographs, purposefully adding a bit of grain to their images.