The technical description is a picture where all the tones are squashed into the brighter end of the tonal scale and where the highlights may be completely ‘clipped‘ (lost). The artistic description is a photo that’s lighter than the photographer intended.
Exposure explained
Exposure is a big, BIG subject. Even today, getting the exposure right is both an art and a skill, and however sophisticated the in-camera metering systems become, the photographer is still the only one who knows what the picture needs to look like.
Essentially, you control the exposure using shutter speed (the length of the exposure), the lens aperture (how much light it lets through) and the ISO setting (the sensor's sensitivity setting). Each of these is a subject in its own right.
Cameras offer a variety of metering systems to measure the light, and you can choose how to control the shutter speed and lens aperture – or let the camera set them both – using the camera's exposure modes.
So here's a selection of articles about everything related to exposure – how it works, the tools available, and why the camera won't always get it right.
Photo by Annie Spratt on Unsplash
Exposure latitude
A term used to describe a film’s tolerance to overexposure and underexposure and its ability to capture tones in the brightest and darkest parts of a scene, even in high-contrast lighting. The modern-day equivalent with digital sensors is dynamic range, though sensors rarely approach the dynamic range (exposure latitude) of film.
Zone System
A system developed by the great landscape photographer Ansel Adams for measuring the light levels throughout a scene and allocating them to ten brightness ‘zones’. The idea was to develop the film to a specific level of contrast that captured the full range of tones and make appropriate artistic interpretations with dodging and burning during […]
Underexposure
Where a picture comes out darker than you expected because of the way the camera has adjusted the exposure, or where you deliberately make the photo come out darker for dramatic effect.
Shutter speed
The length of time the shutter is open during the exposure and usually quoted as fractions of a second. Each shutter speed is half as long as the one before, for example 1/30sec vs 1/60sec. This exposure ‘halving’ is the basis for balancing up lens aperture and ISO settings. A few cameras have external shutter […]
Shadows
The darkest tones in a picture. A pretty vague term (like ‘highlights’) but usually taken to mean the darkest areas where you can still see some image detail. Digital cameras often retain more shadow detail than you can see initially, and this can be brought out later on a computer.
Midtones
Very broadly, the middle brightness tones in a photo. Imagine the full range of tones in an image split into four equal parts – the darkest quarter makes up the ‘shadows’, the lightest quarter makes up the ‘highlights’ and in between are the ‘midtones’.
Metering mode
Digital cameras usually use multi-pattern/multi-segment light metering, but they also offer other ‘metering modes’ – centre-weighted metering (simpler) and spot metering (more precise). The camera will have a button or a menu option for changing the metering mode.
Manual exposure
Where you set both the shutter speed and the lens aperture used by the camera. The camera’s exposure meter may recommend the settings, but you’re free to use or ignore this information. Manual exposure gives you total control but requires some experience.
Long exposure
Long exposures turn moving subjects like water and clouds into an atmospheric blur. The exposure time often needs to be several seconds or longer, so a tripod is essential. In bright light you’ll need a neutral density (ND) filter to get these long exposures.
Light meter
A device for measuring light levels. Digital cameras come with their own sophisticated internal light meters, but it is possible to get external light meters where the settings have to be transferred to the camera manually. This is slower, but has advantages in some circumstances.
ISO (sensitivity)
This setting increases the camera sensor’s sensitivity to light. Each ISO step doubles the sensitivity, so it’s easy to use ISO as another exposure control alongside shutter speed and lens aperture. The more you increase the ISO, though, the more the image quality degrades. Photo by ShareGrid on Unsplash
Histogram
A graphical display of the brightness values in the picture. The darkest tones are at the left and the brightest on the right, and the vertical bars show the number of pixels for each brightness value. Histograms are an invaluable exposure aid when taking pictures, and when editing them later.
Highlights
The lightest tones in a picture. It’s a pretty vague definition, but most photographers take it to mean tones which are at or near a full, featureless white. Retaining or recovering highlight detail – in bright skies, for example – is a big priority for keen photographers.
Grey card
Used for accurate white balance calibration, usually under artificial lighting where the colour of the light sources is unknown or variable. You can use the camera’s manual white balance preset control to take reading from the grey card, or set the white balance using the card and the WB eyedropper tool in many image-editing programs.
EV compensation
Used to adjust the camera’s automatic exposure setting to make the picture come out lighter or darker. Camera meters aren’t foolproof and sometimes you do need to make adjustments. Doing it this way is quicker than swapping to full manual control.
Exposure steps/increments
Digital cameras offer finer exposure adjustments than whole stops (EV) values. By default, they offer 1/3EV adjustments to the shutter speed, lens aperture and ISO setting – though some cameras offer 1/2EV adjustments as an alternative, in line with older film cameras.
Exposure mode
This controls the camera’s operation, from fully-automatic (the camera controls everything), semi-automatic (you can choose the shutter speed or lens aperture) to manual (you choose all the settings).
Exposure Value (EV)
A numerical value given to the amount of light in a scene. For example, bright sunlight might produce an EV of 17. In practice, cameras deal only in shutter speeds and lens apertures and you’re only likely to see EV values on handheld light meters.
Exposure bracketing
Taking a series of shots at different exposure settings in quick succession so that you can choose the best later or combine them in an HDR (high dynamic range) image. See also: Top 12 HDR tips