The phone's cameras

Learning goal

You will be able to explain that each of the cameras on the back of your phone is a separate lens with a separate sensor, and that buttons on the screen such as 0.5x, 1x and 3x switch between these cameras. You will know how wide an area each camera sees, which one is stronger in the dark, and why the image is cropped and enlarged at in-between values; you will notice that when photographing a face, distance matters more than the camera, and you will choose the right camera deliberately in every scene.

The question

Turn your phone over and look at its back. Where there was once a single small hole, today two, three or even four round pieces of glass sit in a row. On the camera screen there are small buttons that match them: 0.5x, 1x, 2x, 3x or more. Most people think these buttons are part of zooming by spreading and pinching their fingers.

Why does my phone have 3 cameras? Because a single small lens can't do every job. Someone shooting with a camera picks a lens from their bag to suit the job: a short one for the whole kitchen, a long one for the sparrow on the balcony. A phone can't change lenses, so it carries several lenses side by side. The 0.5x, 1x and 3x buttons on the screen actually switch between different lenses. In this lesson we will get to know these cameras and learn to switch to the right camera instead of using digital zoom.

Context

When mapping the phone's limits, you saw how hard it is to photograph distant subjects: past a certain point, the phone starts cropping and enlarging the image. This lesson's subject is exactly the area before that point, that is, what you can do with the phone's real lenses. Each lens sees a different width of the scene, and that width changes at the root what the photo tells. Fitting a whole narrow street into the frame is one job; bringing forward a face on the opposite pavement is another.

Getting to know the cameras is an important step in using a phone like a camera. On a camera, choosing a lens is a deliberate decision; on a phone, most people always shoot with the same camera and try to make up the difference by zooming with their fingers. Yet each camera has a character, with strengths and weaknesses. You will see the details of focal length and lens choice later in the lenses module; this lesson is the way to start applying that knowledge on the phone in your pocket.

Simple explanation

What does each camera see differently?

Each round piece of glass on the back of the phone is a separate camera with its own lens and its own sensor. The basic difference between them is the angle of view; that is, how wide a part of the scene the camera sees. The numbers on the screen describe this angle relative to the main camera. 1x is the main camera, the one that takes most everyday shots and is the phone's best camera. 0.5x is the ultra-wide camera and sees an area roughly twice as wide as the main camera sees; it is used to fit a whole room, a wide landscape or a crowded group. A value such as 3x is the telephoto camera, which shows a narrower part of the scene enlarged; it is used to bring a distant subject closer.

These cameras aren't all the same quality. On most phones, the main camera has the biggest sensor and the brightest lens. The ultra-wide and telephoto cameras usually carry smaller sensors. This is hardly noticeable in daylight but becomes clear when the light falls: ultra-wide and telephoto frames get grainy and smoothed more quickly. Some phones, when they decide the telephoto camera won't be enough in the dark, quietly switch to the main camera and crop the middle of the image, even if you press 3x.

What happens at in-between values?

When you spread and pinch your fingers on the screen, the phone does a zoom that looks like a smooth transition between cameras. But real lenses exist only at certain points: for example 0.5x, 1x and 3x. At these points, the image is formed by optical zoom, that is, by the lens itself. At the values in between, for example at 1.7x, the phone usually crops and enlarges the image from the camera one step below. This is called digital zoom, and it can't add detail. That difference between optical and digital zoom is the key to this whole lesson.

On some phones the main camera's sensor has a very high resolution, and there is an extra button such as 2x on the screen. This button usually gives an almost lossless image by cropping the middle of the main sensor, because there are still plenty of pixels in the cropped area. The real problem starts when you go past the longest lens. If you have a 3x telephoto camera and zoom in up to 10x, the phone crops and enlarges the 3x camera's image, and the result is a smudgy image that looks like a watercolor. That is why the safest way is to tap one of the fixed buttons on the screen to choose a lens, and to adjust the frame with your own steps if needed.

Which camera do you choose when photographing people?

What really decides how a face will look is not the camera but the distance. To fit a face into the frame with the ultra-wide camera, you have to get very close. Seen from that close, the nose, which is closest to the camera, looks big, the ears, which are further away, look small, and the face takes on a shape different from its real one. When you photograph the same face with 2x or 3x, you take a few steps back to fill the frame. From that distance, the proportions of the face are much closer to the way we see someone we talk to in everyday life. We will open up the physics of this, that is, that perspective is decided by distance and not by the lens, separately in the lenses module.

When choosing a camera for a portrait, think about the light too. In daylight the telephoto camera is usually the best choice for portraits. But in a dim café or at a dinner, its small sensor can show faces grainy and smoothed. This is the effect that first wipes out the texture and depth of the skin, especially on dark skin left in shadow. When the light falls, going back to the main camera and getting a little closer to the person is the safer way to keep the real detail of the face.

Visual evidence

Picture two portraits of a grandfather sitting in the shade of a tree at a family picnic. In the first frame you switch the phone to 0.5x and get an arm's length from the grandfather. In the photo his nose and cheeks have swollen forward, his ears have shrunk and his forehead has slipped back; the familiar face has turned into a caricature. In the background the picnic blanket, the bags, the cars in the distance and the park sign have all entered the frame and form a messy crowd.

Then you switch the phone to 3x and step back four or five steps from the grandfather. In the new frame the grandfather's face has returned to its familiar proportions; his nose, cheeks and ears are where they belong. The background has narrowed: only a few tree trunks and a green curtain of leaves can be seen, and the mess has stayed outside the frame. On his face in the shade, the texture of his sunburned skin, the hairs of his mustache and the light in his eyes can be made out, because daylight is enough for the telephoto camera. The same grandfather, the same shade, the same phone; the difference is made by which camera you tap and where you stand.

Common mistakes

Summary

Each camera on the back of the phone is a separate lens and sensor; the 0.5x, 1x and 3x buttons on the screen switch between the wide, main and telephoto cameras, while in-between values and anything past the longest lens mean cropping and enlarging the image. Choosing the right camera, standing at a suitable distance especially when photographing faces, and going back to the main camera when the light falls give far better results than digital zoom.

Mini assignment

In this assignment you get to know your phone's cameras one by one.

1. Standing in the same spot, photograph a scene separately with each fixed button on the screen, for example 0.5x, 1x and 3x, and compare how the frame changes.
2. Zoom with your fingers past the longest lens, take one more frame and zoom in on it to see how the detail breaks down.
3. Photograph a family member's face once very close with 0.5x and once from a few steps back with 2x or 3x, and compare the proportions of the face.
4. In a dim room, photograph the same face with the telephoto camera and with the main camera, and note which one keeps the skin texture better.

Check yourself

• Can you say how many cameras your phone has and which one each button switches to?
• Were you able to see where digital zoom starts to ruin the detail?
• Were you able to observe in your own frames that face proportions depend more on distance than on the camera?

Glossary

Mini quiz

1. What do the 0.5x, 1x and 3x buttons on a phone actually do?

• A) They only change the screen brightness
• B) They switch between different lenses and sensors
• C) They change the photo's file size
• D) They set the flash power

2. Why do the telephoto and ultra-wide cameras struggle in dim light?

• A) Because they usually carry smaller sensors than the main camera
• B) Because they can't shoot in color
• C) Because they can't focus
• D) Because they are locked to work only in daytime

3. What happens when you zoom past the longest lens?

• A) The phone switches to a brighter lens
• B) The image gets sharper
• C) The phone crops and enlarges the image and the detail breaks down
• D) The photo is saved in black and white

4. When you photograph a face very close with the ultra-wide camera, why does the nose look big?

• A) Because the ultra-wide camera changes the color
• B) Because of the phone's beauty setting
• C) Because of low light
• D) Because the nose, closest to the camera, looks much bigger than the ears at a very short distance

Answers

1. B — Each button matches a separate camera; the ultra-wide, main and telephoto cameras offer different angles of view with their own lenses and sensors.
2. A — On most phones the main camera carries the biggest sensor; the extra cameras' small sensors get grainy and smoothed more quickly when the light falls.
3. C — Past the longest lens the phone can't switch to a new lens; it crops and enlarges the middle of the current image and gives a smudgy result.
4. D — It is really distance that decides the shape of the face; seen from very close, the nose near the camera grows out of proportion compared with the ears further away.

Summary card

• Each camera is a separate lens + a separate sensor; 0.5x ultra-wide, 1x main, 3x telephoto.
• The main camera is usually the best; the extra cameras struggle in the dark.
• In-between values and anything past the longest lens = cropping and enlarging.
• Distance matters for faces: step back, use 2x–3x.
• Tap a fixed button instead of zooming with your fingers.

Bridge to the next lesson

You have got to know your phone's cameras and you know which one to choose when. The module's last step is to take the phone's decisions fully into your own hands. On many phones a small "pro" or "expert" mode is hidden inside the camera app, and most people shy away from it. The next lesson faces that hesitation: is pro mode scary? There you will see that this mode is a door that opens onto the manual mode of a camera.