We look at pixels every day and most of us know basically what they are, but where do they really come from to do what they do?
As I’m writing right now, pixels are forming these letters and showing them on their right place, and if you scroll your mouse over this line, it’s also made of pixels. The whole screen is constantly reacting to your commands and the system’s needs, whether you’re only scrolling through, editing video, making video games, watching Netflix - everything is shown to you by these tiny colored squares we know as “pixels”.
But the question “Where do pixels come from?” is awfully vague for such a technical matter. So let’s break it down.
What are pixels?
The rough way you can describe it: pixels are one-colored squares that form a digital image.
A pixel is generally thought of as the smallest single component of a digital image. - Wikipedia
So an image can be composed of up to billions of pixels, but most digital cameras, scanners and computers screens go up to a few millions - the more pixels an image has, the more detailed it will be.
But remember, there are the pixels of an image, and the pixels of your monitor. They work roughly the same way, but they are separate things. For example:
You’ve seen this image a lot - it’s Google’s favicon. It’s stretched out way beyond its original size so you can see the individual pixels that form it. These are the image’s pixels.
However, they are being shown to you by your monitor’s pixels.
Yeah, I know.
If you’re ready to have your mind completely blown, check out Hubble’s 1.5 billion pixels view of the Andromeda galaxy. The full size 4.3 gigabytes image is free to download - if you’re brave enough.
How do pixels work?
To put it simply, each pixel can create a single color by combining three: red, green and blue - which form the RGB color space. Every color you see on screen right now is made of just red, green and blue, combining to show each individual color in their right place.
Computers monitors usually have a screen resolution of 72dpi - this is the pixel density. Images from the web usually have at least 72dpi, because that’s the least you can have without pixelating an image in its original size. Zoom in once, and you will start seeing pixels.*
For printing, the DPI is higher, usually 300dpi or more - because imagine looking closer into a business card and seeing pixels. The higher density prevents that from happening. However, for Outdoors, which usually have a printable area of a few meters, pixel density doesn’t have to be that high - in fact, it can be ridiculously low. First, because the higher the pixel density, the higher the file size - so and Outdoor with 9 meters of width and 300dpi would be a huge image file, something close to 1gb. And second, because it’s not necessary - people are supposed to read Outdoors from a distance, so the absurd image quality isn’t needed. Outdoors can be printed with 20dpi or less. Looking closely, they look blurry, but from the right viewing distance, it’s perfect, and it makes handling the file a lot easier and faster.
Our brains tend to see shapes and form images when shown certain patterns. That’s why you see straight lines separating the text you’re reading right now, even though you’re shown only letters. Pixels work similarly. If you take that pixelized Google Icon from above and walk several meters away from the computer screen, eventually you’ll see it in its original size.
*Apple devices with the Retina Display have a screen resolution of 326dpi, which is more detail that the human eye can see - so nothing seems pixelated.
OK, but where do pixels come from?
Technically, it’s easy.
Pixels in digital cameras and scanners come from a CCD or CMOS sensor.
A CCD or CMOS chip is made up of many small electrical receptors that are in a continuous matrix. The matrix of receptors on the camera's or scanner's image sensor converts the light and colors from the projected image into a matrix of pixels in the digital image file. - Source: Trix
But just like in computer monitors, a digital image is a huge amount of data displayed on a grid. Each individual pixel is defined by numbers expressed in bits. To cut it short, pixels in 8-bit systems can give up to 256 colors.
Those old computers with nothing but a black screen and green text were like that because, at the time, those machines could only process two colors.
In the end, pixels are nothing more than numbers. Binary information that when interpreted correctly shows you a different color, and when combining with hundreds, millions or even billions of different interpreted colors, creates a piece of intelligible information like letters or images. Like this last dot - this one, right here.
