Many applications are offering dark mode, the question is how much do they really help save battery and take care of your night vision

Dark mode is all the rage. The number of applications that are incorporating it continues to grow, and yet, this feature causes users to ask ourselves very reasonable questions. Is it really good for our eyes to use it when the night is coming and there is little ambient light? Can it help us sleep better if we use it during the last hours of the day? Does it have any beneficial impact on the autonomy of our devices?

The purpose of this article is to give a well-founded and as objective as possible answer to these questions without letting ourselves be carried away by the myths that circulate on the Internet about this way. After all, it is a resource that is within the reach of many of our devices, such as computers, smartphones or tablets, so if it is true what some brands "sell" to us, it could have a relatively profound impact on both our health as well as the autonomy of the equipment we use every day. Let's see if the dark mode is that bad. Or not.

Dark mode strategies

In recent months, many hardware manufacturers and software developers have introduced this mode of operation in their proposals. In September 2018 it came to macOS, and we can also find it in popular apps and services such as Instagram, YouTube, Slack or most of the Google applications, among other tools. They are even gradually rolling it out on Facebook and it is expected that it will be officially available for WhatsApp soon. Against this background it is inevitable to ask what is the reason why so many brands are joining this fashion, if it is really a fashion.

The dark mode modifies the predominant colors in the interface of the applications to achieve that the screen projects to our eyes a quantity of light significantly less than the usual

And we cannot rule out the possibility that the dark mode really has a tangible impact on our experience. The purpose of this article, as we have seen, is to check it, and one way to approach this objective is to know what effect it has on our devices when we dare to activate it. The most obvious, and the one that all the brands implement, consists of modifying the predominant colors in the interface of the applications to achieve that the screen projects an amount of light to our eyes that is significantly less than the usual one. An effective way to do this is to assign the background of the interface the color black, or a gray tone noticeably duller than the almost “nuclear” white that many applications use by default.

The change of the background color is usually accompanied by the modification of the colors used in the menu bars, the default fonts and other graphic elements of the interface, but, whether or not these modifications are present, they always have the same purpose: reduce the amount of light that the screens of our devices project to our eyes. Curiously, some applications also resort to a second strategy that aims to go one step further in order to increase our visual comfort in that time slot in which ambient light may be in short supply: they act on color temperature.

One of the platforms that has implemented this feature and that gives users some leeway is macOS. And it is that the operating system that governs Apple computers allows us since the update to revision 10.14 Mojave of September 2018 to manipulate the color temperature of the user interface, proposing that we use warmer tones as daylight begins. to become scarce and our natural period of sleep is approaching. Shortly after, in October 2018, Microsoft introduced a similar measure in Windows 10 that also allows us to activate dark mode, and which was supported by the implementation of this same feature in both Office and Edge.

We analyze its impact on the autonomy of our devices

Later in this same article we will investigate the influence that the dark mode has on the health of our eyes and the quality of our sleep, with all that this entails, but it is not the only thing that we have proposed to delve into in this report. . We also find it very interesting to find out if it has any beneficial impact on the autonomy of our devices, and the best way to find out is none other than to test it, so that's what we have done.

The type of panel used on the screen clearly conditions the impact that dark mode has on autonomy.

During our tests we have used four devices similar to the ones many of us use regularly: a Samsung Galaxy S7 Edge smartphone with AMOLED screen, an Apple iMac desktop computer with a 27-inch IPS LED LCD screen, an Apple MacBook Pro laptop with 15.4-inch IPS LED LCD screen and an Apple iPad with 9.7-inch IPS LED LCD screen. As expected, the type of panel used on the screen of each device clearly determines the impact that the dark mode has on autonomy, so it is important to note that the two computers and the tablet incorporate an IPS-type LCD panel. with LED backlight, and the smartphone uses an AMOLED panel.

To carry out the tests on all devices on equal terms, I manually set the panel brightness delivery to maximum and used the recently implemented dark mode in the Slack app, which is available both through the browser and iOS and Android. A note that you may find curious: this is the communication tool that we Xataka editors use every day to coordinate and discuss the topics we prepare for publication. During the test each of the devices only ran Slack, so I avoided using it for anything else. Also, I deactivated the automatic suspension in order to prevent this resource from altering the measurement result.

Dark mode causes screens to emit a much lower amount of light to our eyes.

The first thing I did to open my mouth was to measure the consumption of the desktop computer with a digital wattmeter, both when activating the dark mode and when deactivating it. When enabled, the consumption stabilized around 148 watts, and when deactivated, it consolidated around 152 watts. The difference, as you can see, is minimal, so I decided to do one more test: I measured its consumption with the brightness of the screen at a minimum. This time the wattmeter gave a much lower figure than the previous two, as expected: 58 watts.

As we have just seen, the brightness delivery of the screen has a huge impact on consumption, but in the same light-delivery capacity, the dark mode does not seem to have a significant influence on the consumption of LCD panels. In any case, although it was what I expected, this was only a preliminary observation, so I decided to go ahead with the tests, but this time using the devices equipped with a battery: the laptop, the tablet and the smartphone. The table below these lines shows the results of the autonomy tests carried out under the same conditions that I have described two paragraphs above.

Autonomy tests No dark mode With dark mode Samsung Galaxy S7 Edge (AMOLED panel) 7 hours and 19 minutes 11 hours and 34 minutes Apple iPad (4th generation) with Retina display (IPS LED LCD panel) 4 hours and 34 minutes 4 hours and 37 minutes Apple MacBook Pro (late 2013) with Retina display (IPS LED LCD panel) 6 hours and 2 minutes 7 hours and 4 minutes

The result of the tests leaves no room for doubt: the dark mode has a clear impact on the consumption of AMOLED panels and much more discreet on that of LCD panels. The autonomy of the tablet hardly varied a few minutes when enabling it. That of the laptop itself was increased by around 15%, but this figure pales before the increase in autonomy experienced by the smartphone: nothing less than a value close to 60%. There is nothing. It is evident that the type of panel used in these devices clearly conditions the influence that dark mode has on autonomy.

To understand this behavior we only have to remember how OLED panels (and their derivatives, such as AMOLED) and LCD type ones work. Each of the first self-emitting cells, which are those that use organic diodes, has the ability to emit a specific level of light at a given moment, and also to stop doing so. This ability is responsible for the infinite contrast ratio that OLED panels have, but it has an additional consequence: when one of the cells of the panel stops emitting light in order to restore the black color, its consumption is reduced to a minimum value. . This means that the consumption of each pixel is proportional to the intensity of the light it emits, making it easy to intuit that an OLED screen that has many black pixels consumes less than that same panel with a good part of those cells in the matrix. emitting light to reproduce colors that require greater brightness delivery.

The liquid crystal molecules of each sub-pixel of an LCD panel modify their spatial orientation from the voltage applied to them, which acts on the amount of light that they allow or do not pass.

During our tests the autonomy of the mobile with AMOLED panel increased almost 60% when activating the dark mode

The operation of the LCD panels that many of our devices incorporate is, however, very different. The inorganic diodes that these arrays use are not capable of emitting their own light, so they need to be supported by an additional light source, which is almost always an array of LEDs. There are several strategies that allow us to control the amount of light that each cell of the LCD panel passes through itself. In fact, this is the fundamental difference that exists between IPS, VA and TN panels, which are the most widely used in LCD devices, and the reason why these technologies differ significantly if we stick to parameters as relevant as their contrast. native, angle of view or relative immunity to light leakage.

An interesting note that we are interested in remembering is that each of the cells of an LCD panel does not have a single LED diode associated with it. Each provides the light a set of panel pixels need, and as sophisticated as the backlight dimming technology used is, there is clearly no such strong relationship between the level of light delivered by each pixel. of the panel and its consumption as it happens in OLED panels. If we dim the light provided by one of the LED diodes of an LCD panel to the maximum, we will be depriving a set of pixels in the matrix of light, and this is not always feasible, so this circumstance is unlikely. This behavior explains why an OLED TV consumes less than an LCD TV of the same size when they both play the same content. And also why the dark mode helps us to extend the autonomy of our devices with an OLED panel, but not so much that of those with an LCD screen.

Dark mode and its impact on eyestrain and sleep

To investigate the influence of this modality of use on our visual well-being, it is time for us to review briefly what is the function of two of the most important structures of our eyes: the retina and the pupil. As we all know, the latter is a circular hole located in the center of the iris and with a variable diameter that is responsible for controlling the amount of light that enters the interior of the eyeball. Two muscles are in charge of manipulating its size, which manage to close or dilate it depending on the amount of light in our environment. If the light is abundant, the pupil contracts, and if it is scarce, it dilates.

Our brain interprets the information sent by the retina to reconstruct the images captured by our eyes

The role of the retina is very different. And it is a tissue formed by several superimposed layers of nerve cells that have a very complex structure. It is housed on the inner surface of the eyeball and has a function similar to that of film in analogue cameras or the sensor of digital cameras: to collect light that falls on its surface. When the photons collide with the most superficial layer of the retina, they trigger a series of stimuli and electrochemical processes in the innermost layers of this structure that aim to generate the nerve impulses that will travel to our brain through the optic nerve.

Our brain is the organ responsible for interpreting the information sent by the retina, so it is able to use it to reconstruct the images before us. If we turn to our analogy with digital cameras again, the electronic component that performs this same function is the image processor. Now that we have reviewed what the pupil and retina are for, we can go on to describe what happens when we find ourselves in a space with very little ambient light.

1. Posterior chamber 2. Anterior chamber 3. Cornea 4. Pupil 5. Uvea 6. Iris 7. Ciliary body 8. Choroid 9. Sclera 10. Suspensory ligament of lens 11. Lens 12. Vitreous humor 13. Hyaloid duct 14. Retina 15. Ocular macula 16. Fovea 17. Optic disc 18. Optic nerve 19. Retinal blood vessels

If the amount of light collected by our retina is too low, our brain will not have enough information to identify the shape, color and volume of objects. For this reason, in these circumstances, the dilator muscle of the pupil comes into action to increase the diameter of this opening and allow a greater amount of light to enter the interior of the eyeball. The light may still be insufficient for us to see our surroundings clearly, but this strategy is ideal when what we need is to get the most out of our visual system.

If we place a point light source with a relatively high intensity inside a space with very little ambient light, such as the screen of a mobile phone or computer, we will be victims of a phenomenon with which we are all familiar. : the glare. In these circumstances the pupils of our eyes will have expanded to collect as much light as possible, so that when we direct our gaze towards the screen they will find a torrent of photons that will overstimulate our retina. This in turn will cause the optic nerve to transport to our brain a series of nerve impulses with an intensity greater than that which occurs under normal circumstances.

Glare subjects our visual system to a stress that, if prolonged, can cause eye discomfort and headache.

When this phenomenon occurs, which is what we all know as glare, our visual system is under stress of a certain intensity. When we drive at night and a car traveling in the opposite direction dazzles us, the additional fatigue to which our visual system is subjected lasts an instant, but if we use a screen in a dimly lit space for several minutes, or, what is worse, for tens of minutes, this stress lasts over time and can cause eye discomfort, and even headache caused by the overstimulation to which our visual system is subjected, in which, as we have seen, it is involved our brain.

An effective way to avoid this problem requires generously lighting, as far as possible, those spaces in which we are going to use screens. It doesn't matter if the light is natural or artificial; what is really crucial is that it is present in the amount necessary so that the contrast between the screen and the environment is not excessive and our pupil is able to precisely regulate the amount of light that penetrates the interior of our eyeball, minimizing this It forms the possibility of the overstimulation that we have already talked about several times throughout this article. As you can see, so far everything is quite intuitive and reasonable.

However, at this point it is interesting to introduce one more ingredient in the recipe: the blue light emitted by the screens of our devices. This form of electromagnetic radiation is contained within the spectrum of visible light and has a wavelength that ranges from 400 to 495 nm. The interesting thing is that a portion of this range, the one that goes from 400 to 450 nm, is known in ophthalmology as high-energy visible light. Currently there is no absolute consensus about whether or not it has a detrimental impact on the health of our eyes, but some studies, such as the one carried out by a group of researchers from Ohio University (United States), establish a relationship between prolonged exposure to blue light emitted by device screens and macular degeneration.

Much better tied is the impact that blue light seems to have on the quality of our sleep. And there are many studies that argue that exposure to this light during the hours preceding night sleep alters our circadian rhythm. Our biological clock. Circadian rhythms are the physiological variations that living beings experience regularly in response to external environmental stimuli. And one of the most relevant stimuli is light.

Numerous studies argue that exposure to blue light during the last hours of the day alters our circadian rhythm

The feeling of numbness and relaxation that we usually experience at dusk is caused by the impact that light has on the secretion of melatonin, which is the hormone that regulates the physiological state that leads us to sleep, although this is not its only function. During the day the pineal gland, which is the structure of our brain that is responsible for secreting this substance, hardly produces melatonin, but when night falls the level in our body of this hormone reaches its maximum value, which activates the metabolic response that induces us to sleep.

The impact sleep has on our lives is well known. Many scientific studies have explained in detail how important it is to sleep well not only to think clearly, fix memories and react quickly to external stimuli, but also when it comes to fighting irritability and depression. Some research even establishes a direct link between poor quality sleep and some serious illnesses, such as cardiovascular deficiencies or diabetes.

According to experts, the blue light emitted by the screens of our devices can alter our circadian rhythm, so they recommend not using them just before going to bed.

Blue light is naturally present during daylight hours, causing the inhibition of melatonin production to keep us active and vigilant during our daily activity. The problem is that the LED diodes used by the screens of our devices emit visible light with a wide wavelength that contains the range of blue light. Numerous studies, such as the one carried out by a group of researchers from the New York Center for Light Research, have proven that artificial light causes the suppression of melatonin segregation, so the use of screens shortly before leaving going to bed can significantly impair the quality of our sleep.

In addition, the stimuli offered by some of our devices, such as mobile phones, make it difficult for us to reach the appropriate state of relaxation to fall asleep. Everything we have reviewed so far puts in our hands the tools we need to conclude that the dark mode is a valuable ally both in minimizing eye strain and in combating the alteration of our circadian rhythm by preventing the suppression of secretion melatonin.

Using warmer tones and reducing blue light emission are two beneficial strategies that can help us keep under control the negative impact that screens can have on our sleep when we use them shortly before going to bed.

When we activate the dark mode in one of our devices, the amount of light emitted by its screen towards our eyes is significantly less due to the presence of a dark background. This causes the contrast between the screen brightness and a low ambient light environment to be lower, which, as we have seen, reduces our eyestrain. In addition, some dark modes offer us the possibility of altering the color temperature towards warmer tones, and often also incorporate a blue light filter that, in theory, reduces the amount of light emitted by the screen in the range of lengths of wave that is between 400 and 495 nm.

The use of warmer tones and the reduction of blue light emission are two beneficial strategies that can help us keep under control the negative impact that screens can have on our sleep when we use them shortly before going to bed. According to experts, the ideal is that we stop using our screen devices for a while before going to bed, but we all know that it is something that is not easy to carry out. And in these circumstances the dark mode helps. Everything we have seen helps us understand why, but there are also studies that support this same idea, such as the one carried out by the team of the Spanish chronobiology expert Juan Antonio Madrid. His research describes how beneficial it is to use adequate light to minimize as far as possible the alteration of our circadian rhythm.

Cover image | Daria Shevtsova
Images | Rhcastilhos | Pixabay | Bruce Mars | Marvin Raaijmakers

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