Welcome back to the series, Let’s Talk Cameras (part 2). In our last post, we talked about what cameras are and what they are made up of.

Let’s talk cameras part 2

In this post, we are going to look at some of the most important parts of a camera:

  1. Image sensors
  2. Pixels (or photosites)
  3. Megapixels

1. Image Sensor

This is a piece of equipment that detects and captures the information in an image. It does so by catching light and converting it to an electric signal. An image sensor is an electronic plate with pixels arranged on it. The job of the pixels (also known as photosites) is to catch light, while the sensor circuitry converts the light to electric signals.

Image sensors Lets talk cameras 2
A CMOS image sensor for a digital camera

There are two main types of digital image sensors for cameras:

  • Charge-coupled device (CCD) sensors
  • Active pixel sensor or Complementary Metal-oxide semiconductor (CMOS)

CCD sensors are the more older and traditional sensors. It captures photos in one go. CCD does well in low light but it is expensive and consumes a lot of battery power.

CMOS on the other hand does not capture images at once but it does it bit by bit. CMOS also does not do very well in low light but it is cheaper and does not use up a lot of battery power so it is the sensor of choice for smartphones.


Image Sensor Size

Imagine it is raining outside and you are told to catch the rainwater with wine glasses arranged on a tray for about 10 seconds.

What if for example, you are given a small tray with small glasses? I am sure you’ll agree with me that you would not catch a lot of water. What if a small tray with bigger glasses? That is open to the imagination.

At this point, it would make sense to get a bigger tray right? A bigger tray can contain a lot more glasses which can then catch more water. The tray here is the image sensor and the wine glasses are the pixels.

The size of image sensors in smartphones is very small. They are so small that they are measured in fractions of an inch. The usual size is around 1/2.55 inches (written as 1/2.55”) although some could be as large as 1/1.7” and others as small as 1/5’.

The biggest sensor around arguably is the one on the Huawei P40 series main camera measured at 1/1.28”.

Smartphone cameras let's talk cameras


These numbers seem confusing right? Sure it does.

Understanding sensor sizes

A simple way to understand them is to simply get a calculator and divide the fractions. A 1/3.33” sensor equals 0.3003” while the Huawei P40 sensor of 1/1.28” equals 0.7”. 0.7 is bigger than 0.3 right? It’s that easy.

So between a 1/2.5” sensor and a 1/1.7” sensor, which one is bigger?
1 divided by 2.5 = 0.4
1 divided by 1.7 = 0.588
So as 0.588 is bigger than 0.4, the sensor size of 1/1.7” is bigger than that of 2.5”.

Smartphone sensors are small. This is because there is very little space available on a smartphone.

When buying a phone that boasts a lot of camera ability, it is important to check the size of the sensor. Because the bigger the size, the more pixels you can pack into it.

Remember the tray from earlier? It is not just enough to pack more pixels into the sensor. It is more important to pack in bigger pixels.

Bigger pixels in a sensor can catch light better than smaller pixels. You can only fit bigger pixels into a bigger sensor so in summary, the bigger the sensor, the better the camera. This is why for example, a bigger 1/1.4” 12 megapixel camera with bigger pixels will perform better than a smaller 1/2.0” inch camera with 16mp.

Let's talk cameras part 2

2. Pixels (Picture Element)

Let's talk cameras (part 2)
Pixels on a CMOS image sensor (lets talk cameras part 2)

A pixel is the smallest unit of a digital image. Pixels are the tiny dots that make up a digital image. This means that when you divide a picture into its smallest parts or when you zoom in to its extreme point, what you are going to see are the pixels that make up that image. Pixels are the building blocks of digital imaging.

Pixels are also used in measuring the resolution of an image. Resolution simply means how sharp and clear an image is.

On an image sensor, are arranged photosites (or pixels). These help to catch light images. The sizes of pixels in a sensor are measured in micrometers (µm). Bigger pixel sizes capture more light and perform better at night than smaller pixel sizes.

A camera like the Huawei P40 Pro with a 1.28” sensor and 2.4µm pixel size will wipe the floor with the iPhone 11 Pro Max camera of 1/2.55” sensor and 1.4µm pixel size. If we are going to judge with hardware alone, they are not mates (sorry iPhone fans). The iPhone 11 Pro Max camera also has a smaller sensor than the Xiaomi MI 10 Pro of 108 MP, f/1.7, (wide), 1/1.33″ sensor, 0.8µm pixel size, but the iPhone has bigger pixels natively, while the MI 10 uses pixel binning.

3. Megapixels

A megapixel simply means 1 million pixels. Squeezing 1 million pixels onto an image sensor gets you a 1mp camera. If you can squeeze 12 million pixels into a sensor, you get a 12MP camera. When you can fit 48 million pixels into a sensor, you get a 48MP camera. The addition of more pixels goes a long way to increase resolution and retain details of a photo when zoomed in.

While more megapixels is never a bad thing, as we are now on the horizon of 64 and 108mp cameras, this must be said. The sizes of image sensors are smartphones are very small. So to fit in more pixels, you have to either increase the size of the sensor or reduce the sizes of the pixels.

Most companies usually pick the second option but resort to something called pixel binning which we shall discuss in the next part of this series.

This brings me to the end of this post on Let’s Talk Cameras 2. In our next post on Sunday you will be able to put the knowledge you have gained in this post and the previous one into a practical test by reading camera specs in a smartphone. Don’t forget the comment section is always open for discussion and questions, thank you.

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