Session 3: Camera Control on a Phone

Point a phone at a scene and it instantly guesses the brightness, the focus distance, the colour temperature and the processing. Most of the time it guesses well, which is why phone photography is so accessible and why most people never touch a setting. The problem is that it guesses for the average, and a photograph is usually about the exception.

It fails in predictable ways. Faced with a bright window behind a person, it exposes for the window and silhouettes the person. Faced with a dark room, it brightens everything and produces noise. Faced with a subject that is not in the middle, it focuses on whatever is in the middle. These are not malfunctions — the camera is doing exactly what it was told to do, which is to average.

So the goal is not to take manual control of everything, which would slow you down and mostly make things worse. It is to know the three or four situations where the average is wrong and intervene for those. That is what the rest of this session is: a short list of interventions rather than a manual mode.

Tap the screen and the phone sets focus and brightness for that point. On almost every phone, a small sun icon appears beside the focus box, and dragging it up or down changes the brightness while keeping the focus. That single control fixes most exposure problems and takes a second.

The principle to hold onto is expose for the highlights. A camera can often recover a dark area when you edit; it very rarely recovers a blown-out white, because the detail was never recorded. A bright sky, a white shirt, a white plate of food — if those are pure featureless white, no amount of editing brings them back. It is usually better to have a slightly dark image you can lift than a bright one with nothing in the whites.

Then exposure lock: press and hold until you see AE/AF Lock, and both brightness and focus stay fixed while you move the phone. This is essential whenever you want to focus on one thing and frame another — a face at the edge of the frame, a subject against a bright background — because without the lock, every time you move the phone the camera re-guesses and the exposure jumps.

Phone autofocus is good but it has one habit that ruins photographs: it focuses on whatever is nearest or most central, not on what the photograph is about. Point at a person with a busy street behind them and it may well choose the street, because the street has more edges to lock onto.

The fix is to tap the subject — specifically the eye, for a person, because that is where the viewer looks and a slightly soft nose is forgiven while a soft eye is not. If the subject is not where you want it in the frame, tap to focus, hold to lock, then move the phone to compose. This is called recomposing and it is the standard technique for any off-centre subject.

Focus also struggles in low light and low contrast, where the camera hunts back and forth and never settles. Give it something with an edge: tap a boundary between light and dark rather than a smooth area. If it still will not lock, you are at the limit of the phone, and the honest answer is more light or a closer subject rather than more patience.

White balance is the camera working out what colour the light is so that white things look white. Daylight is bluish, tungsten bulbs are orange, fluorescent and many LEDs are greenish. Automatic white balance handles a single light source well, which is most situations, and fails when there are several at once.

The failure is visible as a colour cast: everyone at a party lit by warm bulbs looks orange, a room under mixed bulbs and daylight has half the people warm and half cool. Sometimes that is fine and even attractive — warm evening light is pleasant — but for product photography it is a real problem, because a customer who receives an item that is not the colour in the photograph will complain, and rightly.

The practical rules are simple. Remove competing light sources where you can — turn off the bulb and use the window, which gives one clean colour. Use something white in the frame as a reference so you can correct the cast later with confidence. And if your phone offers a manual white balance or a raw mode, use it in mixed light, because raw records the data without baking in a colour decision you cannot undo.

HDR takes several exposures and merges them so that both bright and dark areas hold detail. It genuinely helps in high-contrast scenes — a person against a bright sky, an interior with a window — and it is on by default for good reason. But it has three failure modes worth knowing: it smears movement, so it is wrong for anything in motion; it kills deliberate silhouettes, because the whole point of a silhouette is lost shadow; and it can flatten mood in a dark, atmospheric scene by lifting shadows you wanted dark.

Raw — DNG on Android, ProRAW on some phones — records far more information than a JPEG, at the cost of a much larger file and the need to edit it. A raw file looks flat and dull straight out of the camera, which surprises people; that flatness is the point, because it means the data is still there. Shoot raw when the light is difficult, when you plan to edit seriously, or when you might want to fix white balance later. Shoot JPEG when you need the file small and the image finished.

Then stability, which decides whether any of this matters. In low light the phone uses a slower shutter, and movement becomes blur. Hold the phone with both hands, elbows tucked against your ribs, and brace against a wall, a table or a doorway. Use the volume button or a timer rather than tapping the screen, because the tap itself moves the camera. And do not pinch-zoom — on most phones that crops the image and discards resolution; switch to the phone's second or third lens if it has one, which is a real optical change.