Who has not come across a similar one - you are working on a fundamental problem on your own computer, the percentage of the battery charge becomes low, and the charger is far away. Will switching to a darker theme help extend the battery life of my computer?
Let's find out when switching to a darker theme really saves energy and when it doesn't.
First, we need to understand how the different types of displays work.
Liquid crystal display (LCD)
Liquid crystal displays (LCDs) are multilayer screens that, as the name suggests, are composed of liquid crystals. Liquid crystals do not glow by themselves, so a light source is needed to make an image visible on a liquid crystal display.
Therefore, the first layer consists of several cold cathode fluorescent lamps (CCFL). They are usually located behind the liquid crystal layer and shine through it, although side illumination is also common, for example, in watches.
Then we have an LCD, which consists of glass plates with liquid crystals sandwiched between them. An integral part of LCDs is also a polarizing filter, which is used for image formation and brightness control.
The amount of light passing through the polarizer and crystal layer can be controlled by applying voltage to the electrodes. Crystals change their orientation depending on the electric field, and a certain amount of light is polarized.
Light emitting diode (LED) graphic display
LED monitors differ from LCDs in only one way - they have only one difference from LCDs, and that is the backlight. Instead of cold cathode fluorescent lamps, they use a multi-LED backlight (usually 3 LEDs per pixel, one red, one green and one blue).
These LEDs are driven by a sophisticated circuitry that allows each pixel to be selectively colored and illuminated. Brightness is controlled by liquid crystals and polarizers in the same way as in LCDs.
OLED display
OLED (Organic Light-emitting Diode) displays are the latest development in this field. Unlike LCDs and LEDs, OLEDs use organic semiconductors that emit visible light when an electric current is passed through them. OLED displays are so small that individual pixels can be illuminated directly, eliminating the need for a backlight and LCD panel.
How is energy spent in dark mode?
Dark Mode works differently on different monitors. LCD displays use a backlight that glows at a constant intensity. In order to darken the screen, the electric current interacts with the crystals in such a way that the light is blocked, as a result of which the charge is consumed.
In OLED displayson the other hand, the dark theme is activated by turning off certain pixels to save energy. It turns out that dark mode on OLED screens saves energy, but not always on LCDs.
The power consumption of OLED displays in dark mode depends on the brightness of the display and the app interface. The brightness of the display depends on the intensity of the pixel backlight, which is defined as the number of normally incident energy (i.e., light incident perpendicular to the surface) per unit area in unit of time. The higher the intensity, the higher the energy consumption.
American scientists from Purdue University even spent studyby comparing how much electricity is consumed in light and dark mode. To do this, they launched applications such as YouTube, Google News, Google on several devices. Calculator, Google Maps, Google Calendar, etc., and measured how much electricity they use in a light mode. The apps then switched to dark mode and compared the metrics.
The results showed that dark mode does save power, but that this is only true for OLED displays. This is because their design is such that in dark mode, no additional energy is required to block light by acting on the crystals, as in LCDs. Instead, individual pixels can be turned off, creating dark areas and illuminating only parts of the screen that are needed.
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