Manual mode transfers exposure control from the camera's metering algorithm to the photographer. In automatic mode (Program, Aperture Priority, or Shutter Priority), the camera's TTL (through-the-lens) metering system selects exposure values targeting 18% middle grey reflectance. Manual mode (designated "M" on Canon EOS, Nikon Z, Sony Alpha, and Fujifilm X-series mode dials) overrides this automation, giving the photographer direct control over all three exposure parameters.
Manual exposure relies on three interdependent variables: aperture diameter, shutter duration, and sensor sensitivity (ISO). Each full-stop change in any one variable doubles or halves the light reaching the sensor. This guide defines each variable, explains the mathematical relationship between them using the Exposure Value (EV) scale, and provides specific numerical references for common shooting scenarios.
Understanding the Exposure Triangle
The exposure triangle defines the relationship between three variables that determine image exposure: aperture (f-stop), shutter speed (seconds), and ISO (sensor sensitivity). Each variable operates on a logarithmic scale where one full stop represents a 2x change in light. The Exposure Value (EV) scale quantifies this relationship: EV = log2(f-number² / shutter speed). At ISO 100, EV 0 equals an exposure of f/1.0 at 1 second. Typical daylight scenes measure EV 13-15, while indoor environments measure EV 5-8. For a detailed breakdown of how these three variables interact, see our complete guide to the exposure triangle.
Aperture controls depth of field (the zone of acceptable focus in front of and behind the focal point). Shutter speed determines motion rendering (frozen at fast speeds, blurred at slow speeds). ISO amplifies the sensor signal, increasing brightness at the cost of introducing electronic noise. These secondary effects make each variable a creative control as well as an exposure control.
Aperture: Controlling Depth of Field
Aperture is the adjustable diaphragm inside a camera lens that regulates the diameter of the light-transmitting opening. The f-stop number equals the lens focal length divided by the aperture diameter. A 50mm lens set to f/2 has a 25mm aperture opening; the same lens at f/8 has a 6.25mm opening. The standard full-stop f-number sequence is: f/1.0, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. Each full stop halves the light-gathering area of the previous stop.
Aperture diameter directly determines depth of field (DoF), the range of distances from the lens within which objects appear acceptably sharp. At f/1.4 on a 50mm lens focused at 3 metres, the DoF extends approximately 0.13 metres. At f/11 with the same lens and focus distance, the DoF extends approximately 3.2 metres. Portrait photographers use apertures of f/1.4 to f/2.8 to isolate subjects from backgrounds. Landscape photographers use apertures of f/8 to f/16 to maximise sharpness across the frame.
Lens resolving power peaks between f/5.6 and f/8 on most designs. Beyond f/11, diffraction begins to reduce per-pixel sharpness on sensors with pixel pitches below 5 micrometres (common on 24MP APS-C and 45MP+ full-frame sensors). Apertures of f/16 and f/22 produce visible diffraction softening on high-resolution bodies such as the Canon EOS R5, Nikon Z7 II, and Sony A7R V.
| F-Stop | Aperture Opening (50mm lens) | Depth of Field | Relative Light Amount | Typical Use |
|---|---|---|---|---|
| f/1.4 | 35.7mm diameter | Very shallow (0.13m at 3m focus) | 16x (vs f/5.6) | Low-light portraits, bokeh isolation |
| f/2 | 25mm diameter | Shallow (0.18m at 3m focus) | 8x (vs f/5.6) | Indoor portraits, event photography |
| f/2.8 | 17.9mm diameter | Shallow (0.26m at 3m focus) | 4x (vs f/5.6) | Wedding photography, sports (telephoto) |
| f/4 | 12.5mm diameter | Moderate (0.52m at 3m focus) | 2x (vs f/5.6) | Travel photography, general outdoor |
| f/5.6 | 8.9mm diameter | Moderate (0.78m at 3m focus) | 1x (reference) | Group portraits, documentary |
| f/8 | 6.25mm diameter | Deep (1.24m at 3m focus) | 1/2x (vs f/5.6) | Landscape, architecture, street |
| f/11 | 4.5mm diameter | Deep (2.6m at 3m focus) | 1/4x (vs f/5.6) | Landscape (near-to-far sharpness) |
| f/16 | 3.1mm diameter | Very deep (7.3m at 3m focus) | 1/8x (vs f/5.6) | Deep landscape, macro (with flash) |
| f/22 | 2.3mm diameter | Near-infinite at moderate distances | 1/16x (vs f/5.6) | Sun stars, maximum DoF (diffraction applies) |
Shutter Speed: Capturing Motion
Shutter speed defines the duration the camera's mechanical or electronic shutter remains open, exposing the sensor to light. The standard full-stop shutter speed sequence is: 1/8000, 1/4000, 1/2000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 second, 2 seconds, and 30 seconds. Each full stop doubles the exposure duration and the amount of light reaching the sensor. Mechanical shutters in cameras such as the Nikon Z6 III and Canon EOS R6 Mark II operate at maximum speeds of 1/8000 second. Electronic shutters in the Sony A9 III achieve speeds up to 1/80000 second.
The reciprocal rule provides a minimum handheld shutter speed to avoid camera shake: the shutter speed denominator equals or exceeds the effective focal length in millimetres. A 50mm lens on a full-frame body requires a minimum of 1/50 second. A 200mm lens requires 1/200 second. On APS-C bodies (1.5x crop factor for Nikon/Sony/Fujifilm, 1.6x for Canon), a 50mm lens has an effective focal length of 75-80mm, requiring 1/80 second minimum. In-body image stabilisation (IBIS) in cameras such as the OM System OM-1 Mark II (up to 8.5 stops) and Sony A7R V (up to 8 stops) extends these limits proportionally: 8 stops of stabilisation on a 200mm lens theoretically permits handheld shooting at 1/1 second.
Shutter speeds below 1/30 second produce visible motion blur on moving subjects. Exposures of 1-30 seconds render flowing water as a smooth surface and vehicle headlights as continuous light trails. These exposures require a tripod or solid surface to eliminate camera movement.
| Shutter Speed | Light Duration | Motion Effect | Typical Subject |
|---|---|---|---|
| 1/8000 s | 0.000125 seconds | Freezes all motion, including fast-spinning objects | Hummingbird wings, motorsport |
| 1/4000 s | 0.00025 seconds | Freezes fast lateral motion | Tennis serves, water splashes |
| 1/2000 s | 0.0005 seconds | Freezes most sports action | Cycling, running athletes |
| 1/1000 s | 0.001 seconds | Freezes general fast motion | Birds in flight, action sports |
| 1/500 s | 0.002 seconds | Freezes moderate motion | Children playing, pets running |
| 1/250 s | 0.004 seconds | Freezes walking subjects | Street photography, casual portraits |
| 1/125 s | 0.008 seconds | Slight blur on fast subjects | Handheld general photography |
| 1/60 s | 0.0167 seconds | Blur on moving subjects; steady handheld limit (standard lens) | Indoor portraits with flash |
| 1/30 s | 0.033 seconds | Visible motion blur; requires stabilisation or support | Panning shots, low-light handheld |
| 1/15 s | 0.067 seconds | Pronounced motion blur | Intentional blur, dim interiors |
| 1 s | 1.0 seconds | Strong blur; static elements sharp on tripod | Waterfalls, low-light cityscapes |
| 30 s | 30.0 seconds | Extended blur; light trails form | Star trails, vehicle light trails, night architecture |
ISO: Sensitivity and Noise
ISO (International Organization for Standardization) quantifies the sensor's signal amplification. The base ISO for most digital cameras is ISO 100 (Canon, Sony) or ISO 64 (Nikon Z-series). The standard ISO scale doubles with each full stop: 100, 200, 400, 800, 1600, 3200, 6400, 12800, 25600. Doubling the ISO value adds 1 stop of exposure, equivalent to opening the aperture by one full stop or halving the shutter speed. For techniques on managing high ISO values and shooting in dim environments, see our guide to low-light photography tips and techniques.
Higher ISO values amplify both the image signal and electronic noise. Signal-to-noise ratio (SNR) decreases by approximately 3 dB per ISO doubling. Full-frame sensors (36 x 24mm) collect 2.3x more light per pixel than APS-C sensors (23.5 x 15.6mm) at equivalent pixel counts, producing 1-2 stops of noise advantage. The Nikon Z6 III (24.5MP full-frame) maintains a dynamic range above 10 stops at ISO 6400. The Fujifilm X-T5 (40MP APS-C) achieves comparable noise performance at ISO 3200. Micro Four Thirds sensors (17.3 x 13mm) in the OM System OM-1 Mark II produce usable output up to ISO 6400 with noise reduction applied.
Setting the camera to Manual mode with Auto ISO delegates only the sensitivity parameter to the camera's metering system. The photographer controls aperture and shutter speed directly. Canon, Nikon, Sony, and Fujifilm bodies allow configuration of a maximum Auto ISO ceiling (e.g., ISO 6400) and a minimum shutter speed threshold. This hybrid approach preserves depth-of-field and motion control while automating exposure compensation.
Putting It All Together: Equivalent Exposures and the EV Scale
Equivalent exposures produce identical sensor exposure through different combinations of aperture, shutter speed, and ISO. The exposure f/8, 1/125 s, ISO 100 admits the same total light as f/5.6, 1/250 s, ISO 100 and f/8, 1/250 s, ISO 200. Each combination yields the same EV (Exposure Value) but produces different depth of field, motion rendering, and noise characteristics. A photographer selects the specific combination that achieves the desired creative outcome.
The EV scale assigns a single number to each luminance level. Common reference values at ISO 100: EV -2 (deep night sky), EV 3 (indoor room lighting), EV 7 (office fluorescent lighting), EV 10 (overcast sky), EV 12 (open shade), EV 13 (slightly overcast), EV 15 (direct sunlight, the "sunny 16" rule: f/16, 1/125 s, ISO 100). The camera's TTL meter reads the scene luminance and displays the deviation from the selected settings on a -3 to +3 EV scale in the viewfinder or rear LCD. A reading of 0 indicates the settings match the meter's 18% grey reference. Positive values indicate overexposure; negative values indicate underexposure.
Practical Exercises for Learning Manual Mode
Exercise 1 (baseline metering): Place a stationary subject in consistent lighting. Set ISO 100, aperture f/8. Adjust shutter speed until the meter reads 0 EV. Record the resulting shutter speed. Change the aperture to f/5.6 (1 stop wider) and observe that the meter now reads +1 EV (overexposure). Increase shutter speed by 1 stop (e.g., from 1/125 to 1/250) to return the meter to 0 EV. This exercise demonstrates the reciprocal relationship between aperture and shutter speed.
Exercise 2 (depth of field comparison): Photograph a subject at f/2.8, f/8, and f/16. For each aperture change, adjust shutter speed to maintain 0 EV on the meter. At f/2.8, the background renders as a blur. At f/8, background details become partially distinguishable. At f/16, background elements appear sharp. The exposure remains constant across all three frames; only depth of field changes.
Exercise 3 (motion rendering): Photograph a moving subject (e.g., a person walking at 5 km/h) at 1/1000 s and 1/30 s. At 1/1000 s, the subject appears frozen with no motion blur. At 1/30 s, the subject's limbs show directional blur across approximately 40 pixels on a 24MP sensor. Compensate for the 5-stop shutter speed difference by opening the aperture 5 stops or increasing ISO by 5 stops (e.g., ISO 100 to ISO 3200).
- Aperture (f/1.4-f/22) controls depth of field and admits light proportional to the square of the f-number ratio
- Shutter speed (1/8000 s to 30 s) controls motion rendering and exposure duration
- ISO (64/100 to 25600+) amplifies sensor signal, trading noise for exposure latitude
- One full stop in any variable equals a 2x change in light; the three variables form a closed system of equivalent exposures
- The reciprocal rule sets minimum handheld shutter speed: 1/(focal length x crop factor)
- The EV scale (EV -2 to EV 15+) quantifies scene luminance; the sunny 16 rule assigns EV 15 to direct sunlight at ISO 100
In manual mode, the camera's built-in light meter continues to function as a reference instrument. The meter displays the difference between the selected exposure settings and the metered scene brightness, typically on a scale from -3 EV to +3 EV in 1/3-stop increments. A centred reading (0 EV) indicates the selected settings match the meter's 18% grey target. The photographer adjusts aperture, shutter speed, or ISO until the meter reading matches the desired exposure, or deliberately offsets from the meter reading to produce intentional overexposure or underexposure. This metering feedback loop forms the operational basis of manual exposure control on all modern DSLR and mirrorless camera systems from Canon, Nikon, Sony, Fujifilm, Panasonic, and OM System.