Many digital photographers don’t dare switch their cameras from auto to manual exposure mode because they’re afraid to unleash the three-headed exposure monster: ISO, shutter speed and aperture.

This five-part series of articles will help you tame that monster.

• Part 1 is about ISO.

• Part 2 explains the second head of the exposure monster, shutter speed.

• Part 3 explains the third head, aperture.

• Part 4 explores the direct correlation between aperture and depth of field.

• Part 5 focuses on the aperture priority mode and shutter priority mode.

ISO is a number that represents the light sensitivity of your digital camera’s sensor. (ISO is an acronym for International Organization for Standardization, which sets those numerical values.) ISO is digital photography’s equivalent of the ASA numbers in film-based photography.

Shutter speed is a measurement of the time your camera shutter is open, allowing light to enter and expose the picture.

Aperture is a number that represents the size of your camera lens opening.

When you understand the relationship of these three exposure settings, and use them correctly, you’ll quickly advance your digital photographer skills—and you’ll tame the three-headed exposure monster. Disturb the monster by failing to learn how to exposure your pictures manually, and it could cause your digital photos to look…well…monstrous.

What scares so many digital photographers about ISO, aperture and shutter speed is that it’s necessary to pay attention to all three simultaneously. It’s a bit like juggling three balls; you must look at all three continuously. If you fail to do so, then you’re apt to drop the other two balls. The same applies to the three-headed exposure monster: When you change one, you affect the other two; so you must keep them in balance or the results are improperly exposed pictures. Fortunately, you’re shooting digital photography, and not film photography. You can take all the images you want, to learn and practice the information and tips in this five-part series.

ISO

The light sensitivity of the camera’s sensor is presented as a range of numbers. The sensor is less sensitive to light at the lowest number. For example, 100 ISO is typically a “normal” setting, which produces a sharp picture because the graininess of the image is fine. Think of sandpaper as a metaphor. A higher number will be more sensitive to light, which makes for a grainer photo, much like coarse-grain sandpaper.

In some cases, shooting at a higher ISO setting could be the right choice, even though that will reduce the sharpness of your pictures. Because a higher ISO setting allows for a higher shutter speed, a sports photographer, for example, shooting a basketball game, where flash is not allowed, is able to freeze the action and take exciting digital photos; they may just be a bit grainer. This also holds true for any interior space with low light, and where flash is not permitted, such as concerts, museums, churches, etc. Without understanding this relationship between ISO and shutter speed, the sports photographer couldn’t do his or her job.

There are four elements to consider when choosing an ISO setting.

• Lighting: Is the subject in direct or indirect light? How bright is it?

• Grain: Should the photo have a fine grain, or is a coarse grain acceptable?

• Camera Support: Are you shooting hand held or on a tripod?

• Movement: Is the subject or objects still or moving?

The answers to these questions will help you determine the proper ISO setting.

• If the subject is well lit, then you can choose a low ISO that will expose the subject correctly and give your digital photo a fine grain.

• If you’re shooting from a tripod and your subject is not moving, then you can also choose a low ISO.

• If the room or environment is dark or the subject is only indirectly lit, then you’ll need a higher ISO, which will create some graininess (as in the basketball arena in the example above).

• If you must hand hold your camera and the subject is moving, then choose a higher ISO number. You can shoot at a faster shutter speed, which will give you a good exposure, but more graininess again.

Once you practice the tips in Part 1, move to Part 2 to learn about shutter speed.

Recommended Reading:

• Understanding Exposure: How to Shoot Great Photographs with Any Camera
• Understanding Shutter Speed: Creative Action and Low-Light Photography Beyond 1/125 Second
• BetterPhoto Basics: The Absolute Beginner's Guide to Taking Photos Like a Pro
• The BetterPhoto Guide to Digital Photography
• The Digital Photography Book
• Creative Shutter Speed: Master the Art of Motion Capture

Image credit: flashdevelop / 123RF Stock Photo