Photography 101.
Learn your camera.

A camera records light reflected from a subject. The lens forms an image, the sensor records it, and the camera turns that information into a photograph. A camera cannot record the same clean detail in complete darkness as it can when enough light reaches the sensor.

Follow the light

• Lens: directs and focuses light to form an image.
• Aperture: an adjustable opening in the lens. It controls how much light passes through at a time.
• Shutter speed: how long the sensor records light for each photograph. Some cameras use an electronic shutter rather than moving shutter curtains.
• Sensor: turns the recorded light into an electrical signal.
• ISO: changes how that signal is used to produce image brightness.

Focus and brightness are different jobs

Focus determines which distance looks sharpest. Exposure settings help determine brightness and the appearance of motion and depth. A bright photograph can still be out of focus. A sharply focused photograph can still be too dark.

Find these controls before continuing

Locate aperture, shutter speed, ISO, the focus mode and the playback display. Look for M (Manual), A or Av (Aperture Priority), and S or Tv (Shutter Priority). Names differ between brands. Use your camera manual to find a control rather than changing settings at random.

Try it: frame the same stationary object, focus on it, take a photograph and review it. Identify the shutter speed, f-number and ISO shown with the image. Those three values will appear throughout these lessons.

Depth of field is the range of distances that looks acceptably sharp in a photograph. You focus at a particular distance; some space in front of and behind that distance may also look sharp. It is a gradual change, rather than a wall where sharpness suddenly stops.

Shallow or deep?

A shallow depth of field can separate a face, flower or animal from a distracting background. A deeper depth of field can help show several subjects or explain the surrounding habitat. Neither is automatically better. Choose according to what the photograph needs to communicate.

Aperture connects sharpness and light

A low f-number, such as f/2.8, means a wider opening. Compared with f/8 on the same lens and composition, it admits more light and gives a shallower depth of field. A higher number means a smaller opening and usually a deeper depth of field, but admits less light.

The available apertures depend on your lens. A lens that starts at f/5.6 cannot be set to f/2.8. Very small apertures can also soften fine detail through diffraction; the highest f-number is not automatically the sharpest choice.

Focus distance matters too

Focusing closer reduces depth of field. With the same camera position and f-number, using a longer focal length also gives a shallower depth of field. Background distance affects how blurred the background looks. Aperture alone cannot explain every result.

Remember: selecting a new focus point changes where the sharpest distance is. Changing aperture changes how much depth looks sharp around that distance. These are different controls. You will test both with the three-object experiment below.

Shutter speed is the duration of an exposure. 1/1000 second is a short recording time. 1/30 second is much longer. When the denominator gets bigger, the fraction gets smaller: 1/1000 is faster than 1/100.

Movement takes place during the exposure

A fast shutter can make a moving subject appear still. A slower shutter records more of its movement as a blur or trail. The speed you need depends on the subject, its direction and distance, and how large it appears in the frame. A walking person and a spinning fan do not need the same setting.

The light trade-off

Keeping aperture, ISO and the lighting fixed, a longer exposure records more light and produces a brighter image. A shorter exposure records less and produces a darker image. Moving from 1/250 to 1/500 second halves the recording time and the light collected.

Two different kinds of blur

• Subject motion: the subject moves while the sensor is recording.
• Camera shake: the camera moves during the exposure.

A tripod helps with camera shake. It does not freeze a moving subject. Stabilization can help steady the camera, but it does not stop the subject either.

Try it: photograph a moving hand at several shutter speeds. Compare the hand with the stationary background. Keep the camera supported and check whether the whole frame is blurred or just the moving part.

The fan experiment below makes this difference easier to see. Its goal is to choose what movement looks like, rather than memorize one shutter speed for every situation.

On a digital camera, ISO helps determine how the recorded signal becomes image brightness. Raising it generally makes the image brighter when shutter speed, aperture and lighting stay fixed. It does not open the lens wider or give the sensor a longer exposure.

Start with a simple sequence

ISO 100, 200, 400, 800, 1600 and 3200 are full-stop steps. Going from 400 to 800 is a one-stop increase in ISO: the image is rendered approximately twice as bright, until clipping or processing limits intervene. The actual light reaching the sensor is unchanged if the other conditions stay fixed.

Why use a higher ISO?

Suppose a moving subject needs 1/1000 second and your lens is already at its widest useful aperture. If the image is too dark, a higher ISO may give you useful brightness while keeping that motion-controlling shutter speed. It is often better to accept some visible noise than lose the photograph to unwanted motion blur.

Why not use the highest setting all the time?

Higher settings can reduce highlight headroom and make noise more noticeable. The result depends on the camera, available light, exposure and processing. A lower number is not a guarantee of a cleaner image if the photograph is severely underexposed and later brightened.

Keep the experiment under your control

For the ISO exercise, use Manual mode and switch Auto ISO off. Otherwise the camera may quietly choose a different value or compensate for another setting. Outside the exercise, Auto ISO can be a useful tool; the point here is to see exactly which control changed.

After testing ISO, read the noise explanation below. Brightness and the amount of useful light captured are related, but they are not the same thing.

Camera settings work within the light that is actually there. An exposure that works beside a bright window may look too dark farther inside the room. The camera has not become worse. Less light is reaching the subject and returning to the lens.

Amount, direction and contrast

• Amount: how much light is available for the exposure.
• Direction: where the light comes from and how it shapes the subject.
• Contrast: how far apart the bright and dark parts of the scene are.

Soft window light and direct sunlight can make the same subject look very different. Changing settings can alter recorded brightness, but it cannot move the sun, soften a hard shadow or remove a large brightness difference between a window and a dark room.

What changes when the light drops?

You can open the aperture, lengthen the shutter time, raise ISO, add suitable light, or change position. Each decision has a consequence. A wider aperture reduces depth of field. A longer exposure can blur movement. Raising ISO changes output brightness without collecting more photons.

Choose the important result first

For a stationary object, a supported camera may allow a longer exposure and more captured light. For a moving animal, a slow shutter might spoil the moment, so aperture and ISO become more useful choices. The correct response depends on what must stay sharp and what can change.

Try it: photograph an object beside a window and then farther into the same room. Keep all settings fixed first. Observe the brightness change. Then decide which one setting you would alter and explain the trade-off before taking the next picture.

There is no universal indoor setting or outdoor setting. Learning to assess the light is more useful than collecting settings without knowing the scene they came from.

A stop describes a doubling or halving. With aperture or shutter speed, a one-stop change doubles or halves the light captured, when everything else stays fixed. A one-stop ISO change doubles or halves the approximate output brightness; it does not double or halve the light reaching the sensor.

Shutter: double or halve the time

1/1000 → 1/500 → 1/250 → 1/125 → approximately 1/60 second. Each move to the right is about one stop more light. Moving left is about one stop less. Some displayed fractions are rounded.

Aperture: use the full-stop sequence

f/1.4 → f/2 → f/2.8 → f/4 → f/5.6 → f/8 → f/11 → f/16. Each move to the right lets through about half as much light: one stop less. Moving left gives one stop more. Doubling the f-number is two stops, not one.

ISO: double or halve the number

100 → 200 → 400 → 800 → 1600 → 3200. Each move to the right is a one-stop increase in ISO. These changes can compensate for a reduction in captured light, but the image-quality result is not identical to actually capturing more light.

One click is not necessarily one stop

Many cameras use one-third-stop increments. Three clicks then equal one full stop. For example, f/4 → f/4.5 → f/5 → f/5.6 is three clicks but only one stop. Check how your camera is configured.

Balance one change with another

Start with f/4, 1/250 second and ISO 400. Changing to 1/500 loses one stop of light. Opening to f/2.8 restores the captured-light amount. Alternatively, ISO 800 restores approximate output brightness while the sensor still captured half as much light.

Predict it: if you change f/4 to f/8, how many stops do you lose? Two. At fixed ISO, changing 1/250 to about 1/60 second compensates by adding two stops of exposure time.

A histogram is a graph of the tones in the image. Dark tones are on the left, midtones in the middle, and light tones on the right. The height shows how much of the image falls into a particular tonal range. It does not show whether your subject is in focus or where those tones are located.

The graph should suit the subject

A dark scene may naturally put most tones toward the left. Snow or a bright background may push them right. Neither is automatically wrong. A good photograph does not require a centered bell-shaped histogram.

Watch the edges

Data pressed against the right edge can indicate clipped highlights: very bright areas rendered without detail. Data at the left edge can indicate clipped shadows. Consider whether those areas matter. A small lamp reflection is different from losing all the texture in a white bird.

Use the image, the histogram and the camera’s highlight warnings together. A brightness histogram can hide clipping in an individual color channel, so an RGB histogram is useful when strong colors are important.

Know what the camera is showing

The camera’s histogram and warnings usually reflect a processed JPEG preview, even if you shoot RAW. Picture style, contrast and white balance can influence the display. Treat it as a practical guide rather than an exact map of every recoverable RAW value.

Practice without guessing from screen brightness

Photograph a stationary scene in Manual mode at fixed aperture and ISO. Make one image, then a faster-shutter version and a slower-shutter version. Compare how the histogram moves. The darker version generally shifts left; the brighter version shifts right. Check where important detail disappears.

A brightened camera screen can make a dark photograph look convincing outdoors. The histogram gives you another way to judge the recording. It helps you make a decision; it does not make the decision for you.

The exposure triangle is a way to remember aperture, shutter speed and ISO. All three affect image brightness, but they do different jobs. Aperture and shutter time control the light collected. ISO helps control the brightness produced from that recording.

Ask three questions

• Depth: how much of the scene needs to look sharp? This helps choose aperture.
• Movement: should motion freeze or blur? This helps choose shutter speed.
• Brightness: after those choices, what ISO gives a useful result without losing important highlights?

Equal brightness can look very different

In the same light, f/4 at 1/250 second and ISO 400 gives approximately the same brightness as f/5.6 at 1/125 second and ISO 400. The second combination has a smaller opening and a longer recording time. Depth of field and motion blur can therefore change even when brightness looks similar.

f/4 at 1/500 second and ISO 800 can also give similar brightness. It captures less light than the first combination, then uses a higher ISO. You gain a faster shutter, but the detail and noise may not look the same.

A practical decision order

Start with the part of the picture that cannot be compromised. For the fan experiment, motion is the priority, so choose shutter speed first. For three objects at different distances, depth of field is the priority, so start with aperture and focus. Then balance the other controls and check the result.

Manual mode is a learning tool

Manual mode makes it clear which settings you changed. Aperture Priority, Shutter Priority and Auto ISO can also be useful once you understand what they are doing. Using automation deliberately is still making a photographic decision.

Before the experiments: predict what should happen, take the picture, compare the result, and explain any difference. If the result surprises you, check whether an automatic setting changed at the same time.