Screen definition or resolution: what are the differences?

When we look at screen technologies, we often confuse the words “definition” and “resolution”. However, there are many differences between these two overused terms. The following paragraphs explain what characterizes each concept and will help you, incidentally, to shine in society.

The place of new technologies in our daily lives sometimes forces us to acquire new technical knowledge. It’s difficult to find your way around the marketing terms of brands. As far as screens (smartphones, tablets, TVs) are concerned, we regularly see manufacturers using the terms “definition” and “resolution” to highlight the quality of their equipment.
You don’t know the difference between the two? Don’t worry, manufacturers themselves sometimes confuse the two terms.

While some people increasingly use the terms “display resolution” and “pixel density” to separate the two concepts, it is difficult for the consumer to distinguish between them. To make things clearer, we’ve prepared a small explanatory attempt that, we promise, won’t get your brain in a knot.

Definition: the number of pixels

What do HD, Full HD, QHD and 4K have in common? Good question, thank you for asking. All these terms speak of one and the same thing: screen definition. Definition is the number of pixels in a panel. To know the definition of a screen, we multiply the number of pixels arranged on a width by the number of pixels placed on the height. Thanks to this skilful calculation, we obtain the definition of the screen.
For example, a 16:9 format QHD tile consists of 2560 pixels in width and 1440 pixels in height, i.e. a total of 3,686,400 pixels. A 4K panel, on the other hand, displays 8,294,400 pixels (3840 x 2160 pixels).
Manufacturers have recently communicated on Full HD+ or QHD+ definitions. This small “+” appeared as smartphones gradually integrated new screen formats (18:9, 19.5:9, 20:9, 16:10). In these cases, the number of pixels in the width and height change.
For example, a QHD+ display in the 18:9 format consists of 2880 pixels in width and 1440 pixels in height. If you are lost remember that a QHD definition has 1.6 times more pixels than a Full HD definition, 4K/UHD has four times more.

Beware of energy consumption!

A beautiful screen is good, but you still need to be able to power it. You’ve probably noticed that smartphones with QHD displays have a latest-generation processor and GPU.

This is simply due to the resource requirements of these slabs. The higher the definition, the more power and energy the screen needs. For example, a QHD panel requires 1.5 times more power than a Full HD panel. And we’re only talking about a display with a 60 Hz refresh rate. 90 Hz and 120 Hz displays are even more demanding.
Manufacturers must therefore optimize all these parameters while maintaining a suitable autonomy. To design its Galaxy S20 Samsung has chosen to limit the 120 Hz refresh rate to Full HD definition. Combining QHD and 120 Hz would have had a significant impact on the already average autonomy.
Resolution: pixel density

The resolution is the ratio between the definition of the slab (number of pixels) and its size (in inches). In France, it is expressed in pixels per point (PPP), while English speakers speak of pixels per inch (literally pixels per inch). The higher the result of this ratio, the better the resolution.
You can have fun using your calculator to calculate the resolution. But you might get annoyed with the conversion game. We therefore recommend that you use free, more convenient online tools such as PPI Calculator. Enter the definition, screen size and you will get the resolution.
For example, we have compared the resolution of a 6.9″ smartphone and a 12.9″ tablet, both with a QHD definition (2560 x 1440 pixels). We obtained a resolution of 425 dpi for the smartphone and 227 dpi for the tablet.
What do these scores mean? Quite simply that for the same definition, the smartphone screen is more comfortable than the tablet screen. The pixel density being lower, the human eye can more easily distinguish them. This difference is particularly noticeable on texts or games. This does not mean that the race for the best resolution makes sense. Because the human eye also has its limits.

What does the human eye perceive?

Contrary to what one might think, the human eye no longer knows the difference between two resolutions above a certain threshold. Apple, whose Retina technology sets the resolution at 300 dpi, estimates that the human eye can no longer see pixels beyond this limit. In reality, it’s not all that simple.
It all depends on how each user sees and how far away they are from their screen. Experts estimate that the correct resolution is between 300 and 400 dpi, well below the screens of some smartphones, not just the top-of-the-line ones. Below 300 dpi, a normal user is able to distinguish pixels by moving closer to the screen. Breaking the 400 dpi barrier is unnecessary because the screen will be more resource and energy consuming without providing more comfort.
However, there are two exceptions. Some superheroes are able to distinguish pixels up to 600 dpi by gluing the eye to the screen without using a magnifying glass. Above all, virtual reality enthusiasts will see the pixels, with the lens on their helmet magnifying the image. But these cases do not really reflect the general public’s usage.
Now you know the difference between screen definition and resolution. Not only will you no longer be able to let yourself be destabilized by marketing talk, but you’ll be able to shine at the next family dinner.

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