Camera Lounge

What is ISO all about? Well, in short, ISO refers to photographic film’s sensitivity to light. Film with a low sensitivity to light (lower ISO speed rating) requires a longer exposure, and is called slow film, wherease film with a high sensitivity (higher ISO speed rating) to light can shoot the same scene with a shorter exposure and is called fast film.

These principles also apply to digital photography. You can control the ISO settings on your camera and change it shot by shot if you so desire, which is a huge advantage over the more expensive alternative with film as you would potentially have to waste film to change the setting!

When would you choose a slow speed? (low ISO rating)

• when there is plenty of available light, either from flash or sunlight
• when you are using fast shutter speeds
• when you require a sharp, non grainy image

When would you choose a fast speed? (high ISO rating)

• when there is little available light in the evening, indoors, or night photography
• when you are using slow shutter speeds
• when you require a softer, grainy image

Low ISO speeds

• 50, 100, 200

High ISO speeds

• 400, 600, 1800

As a general rule, if you are shooting outside on a bright sunny day an ISO of 50 to 200 should be appropriate. If you are shooting in lower light conditions, indoors or in the evening, a faster ISO such as 400 or higher will be appropriate in order to get the right exposure and to avoid camera shake from a slower shutter speed.
Try it at home!

Don’t take my word for it! Try the following at home:

Evening

1. Shoot an image indoors at night with the lowest ISO setting your camera has
2. Shoot the same image with the highest ISO setting your camera has

Note what happens to the shutter speed at the time, and also note how the images differ in quality when you view the files on your computer.

Feel free to leave a comment with your findings!