Full HD screen on the left and 4K on the right. The 4K displays twice as many pixels over the width!

The UHD (4K, 5K, 6K), new standard?

Today, all our displays display either 1920 x 1200 pixels (or sometimes 1920 x 1080) - we talk about Full HD displays - or 2560 x 1440 px and we talk about QHD displays and finally 3440 x 1440 pixels (21:9 panoramic format) and we talk about WQHD. We are talking about UHD - Ultra-high definition (from 4K, 5K and soon 6K with the new Apple Pro Display XDR) when we are talking about a screen whose definition in pixels on the widest side is close to 4000 pixels (in non- panoramic format). There are therefore many screens with a resolution of 3840 x 2160 (2 x 1920 so 2 x Full HD).

What is the "real" 4K?  - The 4K standard defines a screen whose definition is exactly 4096 pixels wide and not 3840, but the term 4K is now in the public domain. I just draw your attention to a material point because the consequences can be significant: some graphics cards perfectly manage the 4K/3840 but not the "real" 4K i. e. 4096 pixels. So be careful when choosing your graphics card if you are considering buying a screen that displays the "real" 4K. I am thinking in particular of some high-end Eizo monitors.

However, since it is impossible for the naked eye to see the difference, it is common to talk about 4K from a definition of 3840 pixels wide. Since our monitors are often in a 16:10 or 16:9 ratio, this gives us screens of 3840 x 2160 or 4096 x 2160 pixels. In other words, at 24 inches from our eyes, these screens have an invisible pitch. It is no longer possible to distinguish pixels at this distance. We then enter the image completely without being disturbed by this tiny grid on the screen.

A first... historical remark - 4K was created at first to renew the TV screens market and it is unarguable that such big screens needed an improved resolution. Even on a 4K screen in 65-inch resolution is "only" 25 ppi. You need to sit quite far from such a screen not to distinguish the pixels! Yes, for TV screens, but here we're talking about computer screens that are at 24 inches only from our eyes and that are not supposed to display just images...
So it is obvious considering these figures that 4K on our "small" computer screens is over-dimensioned while it could still be improved for TV screens (they're already talking about 8K)... But since the industry can't set several norms at the same time, the TV screens standard is also applied to our screens.

Not without consequences... 

The resolution of UHD displays (4K, 5K or even 6K)

The more pixels your screen has, for the same physical size, the more discreet they will be at a "reasonable" viewing distance. Pitch is used to define the physical distance between two pixels, so the smaller the pitch, the less visible the pixels will be. Today, we talk more about resolution than pitch: i.e. the number of pixels per inch is every 1 inch. The very old 72 ppi concern the resolution of the documents we print - even if it basically amounts to the same thing) is now commonly replaced by 94 ppi on average on 24'' Full HD screens. And indeed, the pixels are now very discreet... but still visible. Here are some common resolution values:

• In 23'' Full HD for example, the pitch is 0.30 mm so the screen displays 96 ppi.
• In 24'' Full HD/ 1920 x 1200 or 30''' QHD / 2560 x 1440, the pitch is 0.27mm and the screen has a resolution of 94 ppi.
• In 25'' QHD / 2560 x 1440, the pitch is only 0.22 mm and the resolution increases to 118 ppi.
• In 29'' panoramic QHD / 2560 x 1080 or 34'' panoramic WQHD / 3440 x 1440 or about 0.27 so a resolution of about 95 ppi.

It should be noted that the human eye no longer perceives any difference in the fineness of detail at 240 ppi on a printed A4 page held at 30/40 cm. However, we look at our screens at least twice as much, i.e. about 70 cm. A 120 ppi screen would therefore give the impression of being perfectly smooth with invisible pixels in these conditions. To which resolution does 4K give access?

• 24-inch at 4K (3840 x 2160) - 0.14 mm pitch, therefore 188 ppi. We are well above the 120 ppi we need at 27,5 inches.
• 30-inch in 4K (3840 x 2160) - 0.18 mm pitch, so 140 ppi, still more than enough to be invisible at 27,5 inches.

The higher the resolution, the softer and more progressive the gradients are...

The UHD and therefore the 4K therefore gives access to almost delirious resolutions! Well, let's not deny our pleasure even if we can see that the best for a television can be a little exaggerated for a computer screen placed not several meters away from us but almost stuck in front of us.

Consequences of UHD: the display of photo details, videos... and texts

Everyone agrees that high resolutions (not to mention the very high resolutions of smartphones) are extremely pleasant on computer screens because you definitely don't see the pixels anymore. For example, the rendering of photos is even closer to the rendering of photo prints. The viewing of the videos is obviously superlative, even more so on OLED screens with such deep blacks.

However, due to software and/or hardware problems, the picture is not so perfect!

4K and displaying details in Photoshop

For us photographers, this changes a little the way of working because when the image is displayed at 100% - which allowed us "yesterday" to observe the details of our images to finalize it, retouch it precisely or even accentuate it - it is much less enlarged in proportion on our 4K screen and the retouching or accentuation work will be done with new markers. In short, it will now be necessary to enlarge the image to 200% or even 300% to find our old landmarks and therefore the sufficient level of detail. It's obviously just a matter of habit because it won't be natural to enlarge our photos to 300% at first!

Note! That said, it will depend on the operating system and your Photoshop version because it will sometimes be possible to use a magnification (zoom) of menus and other software windows so that they occupy the same relative size as on a screen of the same physical size but not 4K.

Other important consequences of 4K: the size of the texts and windows of the interface

Unlike a video monitor or a television or a screen that would only be used by players, our screens must display, in addition to our beautiful images, texts and palettes or other software windows.

And that changes everything!

Since the software has been "designed" for Full HD or QHD resolution (average pitch of 0.27), the text size is perfectly suited for comfortable viewing at about 27-inch. However, when the same software is displayed on 4K (and without software tricks - texts in % and not pixels - in the operating system or the software itself) the texts become very small and therefore often unreadable!

Display of Photoshop CC 2018 menus, in Auto mode or 200% up and 100% down. With CC 2017, the Auto mode (or 200%) was even bigger and the 100% mode a little smaller. New! Photoshop CC 2020 further improves text display.

Let's review the situation at the end of 2019...

The 4K is installed with its advantages but not all the software is ready yet even if the operating systems are up to date... but you still need to update it. That said, I thought in early 2019 that the problem would be completely solved by the end of the year. This is still far from being the case!

1 - Operating systems:

Mac OS, since 10.11 El Capitan and Windows 10 are now compatible with 4K. You will therefore have the possibility in the display preferences of these operating systems to choose the percentage of text magnification. It now works perfectly... in terms of the operating system itself.

MacOS is 4K compatible from El Capitan. Windows is compatible with 4K since Windows 10.

a) Windows 10 - In Windows 10, the text display size can be set in: "Settings > System > Display":

Note that Microsoft could have pushed the idea of the custom setting even further and offered even more choices because the cursor does not act continuously but by jumping (from 25% to 25%). Finally, it should be noted that this slider works even on non 4K screens, unlike Mac OS.

b) Mac OS since El Capitan - 10.11 or High Sierra 10.13 : "Preferences > Monitors"

Note that Mac OS only gives access to this option on Retina, 4K or 5K screens. For example, this option is not available on 24-inch or 25-inch QHD (2560 x 1440) displays, which would need it!

You then benefit from an extremely thin display - very beautiful on Microsoft's Surface Pro 4 for example - but a space occupation of the tools palettes in "usual" inches, so perfectly readable as well as texts that are also perfectly visible.

4K and operating systems : To properly manage 4K - i.e. to be able to display texts and palettes in an enlarged form - a recent operating system is therefore absolutely essential.

2 - Software (Photoshop, etc...) :

It is still very variable at the end of 2019 even if it is improving greatly! For example, it was not until early 2016 that Photoshop CC offered a percentage display option that only became really effective with the latest CC 2019 version! With version CC 2017, the texts were either too large or too small. So a priori, on Mac and PC, it is possible to enlarge the size of windows and other Photoshop texts on a 4K screen by using the "Preferences > Interface > Text" menu.

CC 2018 and 2019 Photoshop Interface Options in the Interface Preferences. It is greyed out here for the interface because I am on a Full HD screen. It is possible to choose either "Auto", 100% or 200%. Notice that this was already the case with the CC 2017 version but Adobe has revised its copy and it is as if the 100 and 200% were different. It is strange, but that's the way it is! Update Photoshop CC 2019 if you have a 4K display.

The most painful thing, even with software from the same brand like Adobe, is to find occasional incompatibilities, so on some software in the suite but so embarrassing that it can become prohibitive.

On X-Rite i1Profiler for example, there is finally some change with the latest version 1.8.1 from the October 2018. It took them long enough!

4K and software: as for the operating system, it is absolutely necessary to update your favorite software... and cross your fingers! In the case of Photoshop, there will be no salvation outside of Photoshop CC well updated in its 2018 and 2019 version. The 4K is therefore not compatible with an "old" computer or an old non-cloud version of Photoshop and there are still many practical incompatibilities that do not allow it to be recommended without reservation.

3 - 4K and multiresolutions: Update !

On MacOS at least (because I could check it from a Mac Pro with two D700 + MacOS Moraje + 2 Full HD screens and a 4K screen) it is possible to mix screens of different resolutions and it will then be possible to choose the percentage of text enlargement only on the detected 4K screen. This menu will not be available on the other screens.

Monitor preferences menu under MacOS only available on 4K displays. The "classic" menu will be displayed on the other screens with a resolution of not 4K.

Which equipment to switch to 4K?

We will study this point in detail on my new page dedicated to graphic cards: Which graphic cards and which connectors for photo retouching and/or 4K?  

Conclusion...

My advice ! In 2019, to switch to 4K, you absolutely must have installed Windows 10 or Mac OS El Capitan at least, install the latest software versions (crossing your fingers so that they have been made compatible with 4K) and you need a recent graphics card with the "good" connector to support a 4K display in 60 Hz. If many older graphics cards still support 4K, it is only in 30 Hz so displaying videos will not be pleasant as well as moving pictures or the mouse quickly. Finally, forget the multi-screens if you don't only have 4K screens. In short, it is difficult to recommend the 4K with your eyes closed because you still need a lot of luck to get everything working in your hardware and software environment.

• In 22-inch Full HD: ideal 1920 x 1080 Full HD definition - Pitch almost invisible but really small texts! Interesting for videographers or players. No additional costs.
• In 23/24-inch Full HD: 1920 x 1080 or 1200 resolution - Pitch visible (but this also depends a lot on the anti-reflection treatment of the panel or from 2016 big progress has been made) but good text size and level of detail in the images.
• In 24-inch 4K: the definition is so important that you absolutely need a recent operating system (Windows 10 and Mac OS El Capitan at least) and make sure that your favorite software is compatible with the 4K. Important extra cost because the display is more expensive and often a new graphics card with the latest 4k/60 Hz compatible connectors is required.
• In 25-inch QHD: 2560 x 1440 - Pitch almost invisible (115 ppi) but texts and details too small unless a software tip allows to display the texts at least larger. Perfect screens for players and videographers who do not want to switch to 4K - not to have to buy a new graphics card - and who can therefore use it as a secondary screen.
  
• In 27-inch Full HD: (1920 x 1200) I don't like it because I find the pitch really too visible from a distance of 27-inch.
• In 27-inch QHD: I prefer by far 2560 x 1440 but then the texts are really small (and therefore the fine details too). Not a fan of this size! but no particular compatibility problem.
• In 29-inch WQHD panoramic, or 2560 x 1080 pixels, the texts are displayed as on a classic 23-inch screen.
• In 30-inch QHD: 2560 x 1440 - The same pitch as in 24-inch/1920 x 1200 so with a good text size and details in Photoshop on older operating systems or software versions. The 4K may well become the new standard but the graphics card will have to follow, have a last generation Display Port connector (1.2) to make everything pass and accept that the details of our photos are less invisible unless they exceed the 100% zoom! A 30-inch in 2560 x 1440 is therefore I believe an excellent compromise for photographers in particular.
• In 34-inch panoramic so WQHD: we find ourselves in the same case as with a 27-inch monitor.
• In 38 and 49-inch, we're also in the same situation.

Advantages of the UHD:

• Very fine and modelled images that are not very enlarged,
• a lot of space to display tool palettes (if you accept lowercase texts),
• an image displayed at 100% is easier to compare to a print run,
  
• more space at 100% to make cropping, but...

Its disadvantages:

• Still a little expensive today because...
• the UHD screen is more expensive,
  
• and you need a recent graphics card if you want a refresh rate at 60 Hz,
• and the latest connectors (HDMI 2.0, DisplayPort or MiniDisplay 1.2 at least),
  
• texts are still often tiny in some software or real bugs are still detected,
• incompatible with multi-monitors in multi-resolution,
• you need to zoom to 300% to get back to a "usual" level of detail in Photoshop.

Next pages...

4 / 8 - Which panel technology? Delta e ?

5 / 8 - Luminosity and contrast ? sRGB or wide gamut?

6 / 8 - Which graphics card to buy?

7 / 8 - Hardware acceleration and Look Up Table?

8 / 8 - What is the purpose of the 10-bit display?