What is HiDPI and why is it key to perfect image quality?

What does HiDPI mean?

HiDPI means “High Dots Per Inch”, which in Spanish would be translated as “High pixel density per inch”. The name under which this technology is marketed varies depending on the manufacturer, with ‘Retina’ being the version that has received the most hype thanks to having a company like Apple behind it.

In short, HiDPI specifies that there is a perfect correlation between the physical pixel of a screen and a virtual pixel. Don’t worry if all of this sounds like Chinese to you because many monitor and computer manufacturers still don’t understand this concept. A little later we will explain what HiDPI consists of with several examples with which you can understand this concept with great clarity.

HiDPI is more important than 4K

The market is full of products that are sold in 4K resolution. However, the industry has never done its homework in this area. 4K is not a standard, although we believe so, and does not have a real number of pixels assigned long or wide, which was the case in previous standards (480p, 720p and 1080p).

So… what is 4K? Its definition does not refer to a screen size or resolution, but rather to a image format which is approximately 4,000 pixels horizontally. Obviously, this definition generates a lot of confusion. For example, a 4K television is one that has a 3,840-by-2,160 pixel matrix with a 16: 9 aspect ratio. And a 4K digital cinema screen is 4,096 by 2,160 pixels, with a 17: 9 aspect ratio.

Density is the question

Now we understand that the definition of 4K itself includes a range of varied resolutions around 4 million pixels in total. Let’s say you go to your trusted store and buy a 3840 by 2160 pixel panel. Is it 4K? Yes. Is it a HiDPI display? It depends on the size of the panel. Let’s go with a few examples to see it more clearly:

• If you are talking about a monitor for computer and has some 32 inches, it is most likely designed to be seen from approximately one meter away. Each physical pixel on the screen will correspond to a virtual pixel operating system. The size of the screen will allow you to have hundreds of icons on your desktop. You can have a lot of applications open in parallel and you will not have problems reading text in any of these windows because the font will be fully readable. And not, we would not be talking about a HiDPI screen, but a LoDPI, since its scale is 1x.

• If said resolution is in a 15 inch laptop, we would have a real problem if the scale was set to 1x. You could not read anything at all as there is no coordination between screen density and system interface. It will be then when we have to activate the pixel duplication, that is, the HiDPI. This will make each pixel on our screen become four (a duplication on the X axis of the screen and another duplication on the Y axis). Now, each square of four physical pixels on our screen will be equivalent to a virtual pixel of 1920 by 1080 resolution, which is a resolution that we know perfectly well. By doing this process, there will be no sharpness problems. The scale must be adjusted to perfection, the text must be seen clearly and there must not be any type of icon or blurry menu on our screen.

• What if we talk about a screen of a 13 inch laptop? At 1x we will have an even bigger problem than with the 15-inch laptop. Y if we double the pixels (i.e. if we get 4 pixels for every virtual pixel) all will still look small. So what happens if we take a 3 by 3 pixel matrix? We will not solve the problem either, since if we convert each pixel into nine, we will have over-braked. In these cases, we will have to choose a different physical resolution. For a screen of 13 inch, Full HD resolution is not suitable. Manufacturers who are serious about their products have historically used the matrix of 1,600 by 900 pixels. So to scale correctly, a 13-inch laptop that wants to have a resolution close to 4K should have a 3,200 by 1,800 pixel panel. It may sound silly (it’s just a few hundred pixels apart on each axis), but its usability will be very different. Objects on the screen will be in the correct aspect ratio, unlike the 3840 by 2160 pixel matrix, which will not look good at all. Oh, and if you were wondering, a 13-inch screen with a 3,200-by-1,800-pixel panel can’t be considered 4K. But it is HiDPI. Curious, right?

What happens when a display or system does not support HiDPI?

Beyond what we just explained in the previous paragraph, there is an added problem when we talk about screens that do not support HiDPIBy the way, they are the vast majority of screens that we find on the market. To simplify the example, imagine that we have a 15-inch laptop in front of us. We know that 1920 by 108o is a correct resolution for a screen of this size. What happens if instead of using a HiDPI screen (that is, the 3840 by 2160 pixels in the previous example) we use a display with a scale of 1.5x instead of 2x? Well, for the entire interface to occupy the same space as in a Full HD, the system would have to be scaled 1.5 times.

But here is something that does not add up. Have you already noticed? It is impossible to get it right. We are going to zoom in on the screen and we are going to display the pixels separately. Since there is no 4: 1, 9: 1, or 16: 1 correlation, each pixel must now physically occupy pixel and a half. And the half pixels they do not exist.

What does the system do then? Make up using the famous aliasing, which is still a blur filter that blurs the pixel to simulate that missing half point. The result is a complete disaster and when given in text it proves that a denser screen is not necessarily better. Pirelli said that “Power without control is useless”, and this is the clear example that manufacturers should start to put the batteries and begin to dose that power. HiDPI is not marketing, but a seal that guarantees that the resolution of a monitor has not been chosen arbitrarily.

What is the difference between HiDPI and Retina Display?

Objectively speaking, none. ‘Retina Display’ is nothing more than a commercial nomenclature that registered apple to refer to your HiDPI compliant displays. When Apple sells us a product with ‘Retina Display’, the apple brand means that the resolution of its products is designed so that no scale problems no fuzzy interfaces. They use the same ‘Retina’ trademark for a 27-inch 5120-by-2880-pixel iMac as with the famous iPhone 4, which had a 3.5-inch screen and a 960-by-480-pixel panel. In both cases, the two products have a screen four times as dense as their predecessors.

Why is 4K getting so much hype and not HiDPI?

Unfortunately, for reasons of marketing. Much is said on the Internet that Apple constantly tries to sell us the motorcycle with its technology, but the truth is that they go ahead when they sell us Retina Display. Taking the previous case of the 13-inch laptop as an example, more than one manufacturer prefers to sell a screen with a wrong resolution (that is, it does not comply with the HiDPI) as long as the label says that it is 4K. That is why we said at the beginning that HiDPI is more important than 4K, since it is useless to have a denser screen if you are going to have one. wrong scale or you’re going to have to squint to get a good look at the files on your desktop.