Understanding Exposure, 3rd Edition

1. Master the Photographic Triangle: Aperture, Shutter Speed, and ISO

A correct exposure is a simple combination of three important factors: aperture, shutter speed, and ISO.

The foundation of photography. The photographic triangle forms the basis of all exposures. Aperture controls the amount of light entering the lens and affects depth of field. Shutter speed determines how long the sensor is exposed to light and can freeze or blur motion. ISO sets the sensor's sensitivity to light, with higher ISOs allowing for shooting in darker conditions at the cost of increased noise.

Understanding the relationships. These three elements work together to create a correct exposure. Changing one requires adjusting at least one of the others to maintain the same exposure. For example, if you decrease the aperture size to increase depth of field, you'll need to either slow down the shutter speed or increase the ISO to compensate for the reduced light.

Creative control. By understanding how these elements interact, photographers can make intentional choices to achieve their creative vision. For instance, choosing a large aperture for a shallow depth of field in portraits, or a fast shutter speed to freeze action in sports photography.

2. Understand Exposure Metering and Creative Correct Exposures

Every photograph is a lie, but it is within that lie that a mountain of truth is revealed!

Metering basics. Camera light meters are calibrated to assume all subjects reflect 18% of the light that hits them (middle gray). This can lead to incorrect exposures for very bright or dark subjects. Understanding this limitation allows photographers to compensate and achieve more accurate exposures.

Creative correct exposures. A technically correct exposure isn't always the most visually appealing or impactful. Photographers should strive for "creatively correct" exposures that best convey their artistic vision. This might involve intentionally under or overexposing certain elements of the scene.

Metering techniques:

• Spot metering for precise control in high-contrast scenes
• Center-weighted metering for general purpose use
• Matrix/evaluative metering for complex lighting situations
• Using exposure compensation to fine-tune automatic metering

3. Harness the Power of Aperture for Storytelling and Isolation

Aperture is the creative force behind what I call storytelling exposures (images that show great depth of field) and singular-theme or isolation exposures (images that show shallow depth of field).

Storytelling with depth of field. Small apertures (f/16, f/22) create a large depth of field, keeping everything from foreground to background in focus. This is ideal for landscape and architectural photography where you want to show the relationship between different elements in the scene.

Isolation with shallow depth of field. Large apertures (f/2.8, f/4) create a shallow depth of field, blurring the background and isolating the subject. This technique is particularly effective for portraits and macro photography, drawing attention to the main subject.

Aperture considerations:

• The "sweet spot" of most lenses (typically f/8 to f/11) often provides the sharpest overall image
• Diffraction at very small apertures can slightly reduce overall sharpness
• Lens choice affects the apparent depth of field (telephoto lenses compress perspective)

4. Utilize Shutter Speed to Freeze or Imply Motion

The function of the shutter mechanism is to admit light into the camera—and onto the digital media or film—for a specific length of time.

Freezing action. Fast shutter speeds (1/500s and above) can freeze fast-moving subjects, capturing crisp details in sports, wildlife, and other action photography. The exact speed needed depends on the subject's speed and direction of movement relative to the camera.

Implying motion. Slow shutter speeds can create a sense of movement through motion blur. This technique is effective for:

• Waterfalls and streams (1/2 second to several seconds)
• Light trails from cars at night (several seconds to minutes)
• Panning with moving subjects (1/15s to 1/60s)

Creative shutter techniques:

• Zoom burst (zooming the lens during a long exposure)
• Multiple exposures (combining several images in-camera)
• Light painting (moving a light source during a long exposure)

5. Leverage Different Types of Light for Compelling Images

Low-light and night photography do pose special challenges, though, not the least of which is the need to use a tripod (assuming, of course, that you want to record exacting sharpness).

Golden hour magic. The warm, soft light just after sunrise and before sunset is ideal for landscapes and portraits. It provides a flattering glow and long shadows that add depth and dimension to scenes.

Harsh midday light. While often challenging, strong overhead sunlight can create dramatic shadows and high-contrast scenes. Use reflectors or fill flash to soften shadows in portraits, or embrace the contrast for graphic, high-impact images.

Overcast and diffused light. Cloudy days provide soft, even illumination that's excellent for portraits, macro photography, and reducing harsh contrast in landscapes. A polarizing filter can help reduce glare and enhance colors in these conditions.

Types of lighting to explore:

• Backlighting for dramatic silhouettes and rim lighting
• Side lighting to emphasize texture and form
• Artificial light (flash, continuous lights) for complete control

6. Master Night and Low-Light Photography Techniques

Whether you've chosen to tell a story, to isolate, to freeze action, to pan, or to imply motion in your image, the light will be there regardless.

Long exposure basics. Use a tripod and remote shutter release to avoid camera shake. Start with aperture priority mode, setting a small aperture (f/11 or f/16) for maximum depth of field, and let the camera determine the appropriate shutter speed.

Light painting. During long exposures, use flashlights or other light sources to selectively illuminate parts of the scene. This technique allows for creative control over the final image, highlighting specific areas or adding colorful effects.

Astrophotography tips:

• Use a wide-angle lens to capture more of the night sky
• Set a high ISO (1600-3200) to gather more light
• Use the "500 rule" to determine maximum exposure time before star trails appear (500 divided by focal length)
• Take multiple exposures and stack them in post-processing to reduce noise

7. Employ Filters and Special Techniques for Enhanced Creativity

Of the many filters on the market today, a polarizing filter is one that every photographer should have.

Essential filters:

• Polarizing filter: Reduces reflections, enhances colors, and deepens blue skies
• Neutral density (ND) filter: Allows for longer exposures or wider apertures in bright light
• Graduated ND filter: Balances exposure between bright skies and darker foregrounds

HDR (High Dynamic Range) photography. Combines multiple exposures of the same scene to capture a wider range of tones than possible in a single shot. This technique is particularly useful for high-contrast scenes like sunsets or interiors with bright windows.

Advanced techniques:

• Focus stacking: Combining multiple images focused at different distances for increased depth of field
• Time-lapse photography: Creating videos from a series of still images taken over time
• Intentional camera movement: Creating abstract images by moving the camera during exposure

Last updated: September 12, 2024