Exposure

Definition

Exposure is the total amount of light that falls on the camera sensor, determining the brightness and tonality of an image. It is the interplay of three fundamental factors: Aperture, Shutter Speed, and ISO (Light Sensitivity).

Exposure Triangle - The Three Exposure Factors

The classic exposure equation is based on three controllable variables:

Aperture (f-stop)

• f/1.4 - Maximum light transmission, minimum depth of field (Cinema Primes)
• f/2.8 - Standard for dramatic portraiture, typical for zooms
• f/5.6 - Balanced depth of field, standard for many documentaries
• f/8.0 - Deep depth of field, landscape shots
• f/16 - Maximum depth of field, special applications

Shutter Speed

• 1/24s (180° Shutter at 24fps) - Standard for cinema, natural motion blur
• 1/48s (90° Shutter at 24fps) - Less motion blur, harsher
• 1/96s (45° Shutter at 24fps) - Very little motion blur, high-speed effect
• 1/120s - Video standard at 50fps PAL

ISO Sensitivity (Light Sensitivity)

• ISO 100 - Native sensitivity, minimal noise
• ISO 400 - Typical for well-lit exterior shots
• ISO 1600 - Standard for interior shots with practical lights
• ISO 3200 - Low-light situations, acceptable noise
• ISO 6400+ - Extreme low-light, significant noise

Exposure Metering - EV Values

Exposure is measured in EV values (Exposure Value):

• EV 5: Dim interior light (approx. 3-5 lux)
• EV 8: Typical office light or overcast day
• EV 10: Overcast day, studio lighting
• EV 12: Bright sunny day outdoors
• EV 14: Snow-covered landscape in sunlight
• EV 16: Direct sun, high contrast

Practical Exposure Techniques

Sunny 16 Rule

A classic rule of thumb for outdoor shooting:

• In sunny weather: f/16 at 1/ISO shutter speed
• At ISO 100: f/16 at 1/100s
• At ISO 400: f/16 at 1/400s

False Color and Zebras

• False Color Display: Overexposed areas are highlighted, underexposed in blue
• Zebra Striping: Overexposed highlights are marked with zebra patterns
• These tools are essential for control during shooting

Exposure Index vs. Nominal Sensitivity

• Underexposure: EI 200 instead of ISO 400 (Pushing factor 0.5) - limited dynamic range, but cleaner
• Overexposure: EI 800 instead of ISO 400 (Pushing factor 2.0) - longer grading time, but higher latitude

Exposure Compensation

Manual adjustments from the meter reference value:

• +1.0 EV: One stop brighter (f/2.8 to f/2.0)
• +0.5 EV: Half a stop brighter
• -1.0 EV: One stop darker
• -1.5 EV: 1.5 stops darker

Professional Exposure Control

On-Set Monitoring

1. Spot Metering on faces (typically 40% from white)
2. Consult Histogram: Aim for an even distribution
3. Waveform Monitor: Monitor luminance distribution
4. False Color Monitoring: Detect overexposure immediately

Exposure Latitude

• Modern Digital Cameras: 10-13 EV dynamic range
• Film Emulsion: 8-10 EV dynamic range
• Safety Margin: +0.5 EV to shadows, -0.5 EV to highlights

Scene-Dependent Exposure Strategies

High-Key Lighting (EV 11-13)

• Flat, well-lit scenes
• Typical for: Comedy, documentaries, corporate video
• Advantage: High flexibility in grading

Low-Key Lighting (EV 6-8)

• High-contrast, dramatic lighting
• Typical for: Thrillers, film noir, drama
• Advantage: Atmosphere, artistic control

Normative Lighting (EV 8-10)

• Balanced lighting
• Typical for: Drama, standard narratives
• Advantage: Natural look, easier grading

Errors and Troubleshooting

Historical Development

• 1891: Thomas Edison - Kinetograph camera with 1/40s at 40fps
• 1932: Weston exposure meter established standardized measurements
• 1961: Nikon - first TTL (Through The Lens) exposure metering
• 1999: Sony HDW-F900 - first 24p HD camera with live histogram