What exposure means
Exposure is the amount of light that reaches the sensor, and therefore how bright the picture looks. Too little light gives dark, noisy footage with crushed shadows. Too much produces bright areas that turn plain white, losing detail that cannot be recovered. Three settings control the amount of light, and each has side effects on the look.
The three controls
Aperture is the size of the lens opening, expressed as an f-number. A smaller number such as f/2 means a wider opening and more light. It also gives a shallower depth of field, so the background looks softer.
Shutter speed is how long each frame is exposed to light. In video, it is written as a fraction of a second, such as 1/50. A slower shutter lets in more light and adds motion blur. A faster shutter lets in less light and makes movement look sharper and choppier.
ISO is the sensor’s amplification. Raising it brightens the picture without extra light but increases noise, a grainy look that is most visible in shadows. Cameras differ in how much noise they tolerate, and many have a “native” ISO or two where the picture is cleanest.
Why video has a shutter rule
In photography, you change shutter speed freely. In video, the shutter speed that gives natural-looking motion is tied to the frame rate. A common guideline, often called the 180-degree rule, sets shutter speed at about double the frame rate. At 24 frames per second that is 1/48, and cameras that do not offer it usually provide 1/50 as the nearest setting. At 30 frames per second it is about 1/60.
The reason is how movement appears. A shutter much faster than this tends to make motion look jittery, while a much slower shutter smears movement. Frame rates have their own effects, covered under frame rates, but the practical consequence is that you largely fix the shutter and use other controls to change brightness.
Many creators break the guideline for a reason, such as a fast shutter for crisp sport or a slower one in low light, but it is a sensible starting point.
Stops: a common measure
Photographers and videographers measure changes in light in stops. One stop doubles or halves the amount of light.
- ISO: moving from 400 to 800 adds one stop. Moving from 800 to 1600 adds another.
- Shutter: moving from 1/100 to 1/50 doubles the exposure time, adding one stop.
- Aperture: each full stop of f-number is a change by a factor of roughly 1.4. The familiar sequence f/2, f/2.8, f/4, f/5.6 changes the light by one stop each step. Going from f/2.8 to f/4 halves the light.
A worked example: suppose you film at 24 fps with a shutter of 1/50, an aperture of f/2.8 and ISO 800, and the picture is correct. You want a deeper focus, so you close the aperture to f/5.6. That is two stops less light, because f/2.8 to f/4 is one stop and f/4 to f/5.6 is another. To compensate without changing the shutter, you raise ISO by two stops, from 800 to 1600 and then 3200. The brightness matches, depth of field increases, and noise is higher. Alternatively, you could add light to the scene, which avoids the noise.
This shows the trade-off: every adjustment has a cost somewhere else.
Neutral density filters
Outdoors in bright light, you may find that even the lowest ISO and a small aperture are too bright at 1/50. A neutral density (ND) filter reduces light evenly without changing color much, letting you keep a wide aperture and a shutter near the guideline. Some camcorders and cameras have built-in ND, and others accept screw-on or magnetic filters. Variable ND filters can cause uneven effects at extreme settings, so check the results.
Reading the picture
Cameras offer tools beyond looking at the screen, and the screen can mislead in sunshine.
- Zebras mark areas that are close to clipping.
- Histograms show the distribution of tones from dark to bright. A graph pushed against the right edge suggests clipped highlights.
- Waveform monitors show brightness across the picture and are more precise.
- False color assigns colors to brightness levels to help with consistency.
Faces typically sit somewhat above the middle of the brightness range. Meters can be fooled by a bright window or a dark background, so check the face, not just the average.
Automatic versus manual
Automatic exposure is useful for fast-changing situations, and phones handle it well. Its problem is that brightness can change during a shot as the camera reacts to a bright object entering the frame. Manual or locked exposure keeps the look consistent from shot to shot, which matters when you cut clips together. Many cameras allow a middle path: set aperture and ISO, or lock exposure with a tap.
Exposure and the look of a high-contrast scene
Cameras capture a limited range between darkest and brightest. High dynamic range footage and flatter profiles hold more detail in highlights and shadows, but they require more careful grading. If you shoot in a flat or log profile, you typically need to expose carefully and adjust the colors later. Basic color grading becomes easier with a correct starting exposure.
A simple routine
- Choose frame rate and set the shutter near double that rate.
- Set the aperture for the depth of field you want, remembering the lens and focal length.
- Adjust ISO to get proper brightness, staying as low as practical.
- If it is still too dark, add light. If it is too bright, use ND or a smaller aperture.
- Check faces, highlights and white balance, then lock settings before recording.
Practice with a static scene, change one setting at a time and note the effect. That habit teaches the relationships more quickly than any chart.