en:wiki:eyes-protection

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en:wiki:eyes-protection [2019/03/15 01:52] (Version actuelle)
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 +{{  :​wiki:​oeil.jpg?​nolink&​400}}
 +
 +====== Reduce eye strain on screens ======
 +
 +I often work on my computer. My eyes are often immersed on the screen for long hours, so it is essential to protect them to preserve your vision. Here are some tips to rest your eyes while standing in front of a screen.\\
 +\\
 +Some advice may seem unimportant,​ but none is given at random.
 +
 +<note important>​**If you don't have enough time to read this page**, by far the most important advice is to install **[[:​en::​wiki:​eyes-protection#​filtering_softwares|a color filtering software]]** . This software alone will greatly reduce visual fatigue.</​note>​
 +
 +===== Screen type and frequency =====
 +
 +  * For **LCDs** ​ (liquid crystals, which you most likely have):
 +      * If the display is connected by a **VGA** ​ connector:
 +        * It may be useful to lower the refresh rate in the graphics card settings. With high frequencies (and medium quality equipment), pixels tend to "​drool"​ to the right (very visible on vertical lines), a phenomenon that is avoided by reducing the frequency to 60 Hz (in the settings of the **graphics card** ​ on the computer). However, a very high frequency screen (144Hz...) does not pose this problem, as the flickering is no longer perceptible to the eye.
 +        * Also remember to use the "​automatic calibration"​ in the settings of your **screen** ​ to avoid a burr effect of the vertical lines:
 +
 +|  {{:​wiki:​lignes-verticales-bavures.png?​nolink&​}} ​ |  {{:​wiki:​lignes-verticales-correctes.png?​nolink&​}} ​ |
 +|  Image not adjusted: The pixels "​drool"​. ​ |  Fitting image: Lines are sharper. ​ |
 +
 +  * For digital connectors (**DVI, DisplayPort,​ HDMI...**) changing the frequency is useless, and the calibration is in principle automatic.
 +
 +  * For **CRTs** ​ (cathode ray tubes, now rare):
 +      * Increase the scanning frequency. 60 Hz is insufficient. Try at least 75 Hz or more if your display supports it, even if it means lowering it to resolution (1024×768 or 800×600 instead of 1280×1024). Some people are more sensitive than others to the scanning frequency, but even if you don't see it, it tires your eyes.
 +
 +===== Display resolution =====
 +
 +  * For **LCD** ​ screens, it is **imperative** ​ to use **exactly** ​ the resolution of the LCD for the graphics card, otherwise the monitor will make approximations and all letters will give the impression of "​drooling",​ with blurry (very tiring) edges. The display resolution can be changed in the settings of the graphics card on the computer.
 +
 +  * For CRT displays, the choice of resolution is less restrictive.
 +
 +===== Position =====
 +
 +  * The screen should be facing you, not on the side.
 +  * Adjust the vertical orientation of the screen and the height of your seat to look slightly down, especially if you wear progressive lenses. Do not work with the screen on the side, too high or too low. If the line of your gaze drops almost to the level of the keyboard, consider raising the screen a little higher.
 +  * Arrange your workstation to avoid glare on the screen. For example, avoid working with your back to a window or strong light.
 +  * Prefer matt, not bright screens. ((This is an absolute nuisance since the majority of laptops are sold with bright screens.))
 +  * Ideally, the room where you work should have blinds to modulate the light coming from the outside. Also avoid working with the sun in your eyes.
 +  * It is also not good if the rest of the room is too dark, because it would create too much contrast between the screen and the rest of the room.
 +  * Avoid direct lighting. Prefer indirect lighting. Typically, a desk lamp is too bright direct lighting. You can turn it over and direct it to a white wall.
 +  * Avoid most LED lighting. Most LED lights sold send too much UV (ultraviolet) light, which is bad for the eyes (In addition, many LEDs have a very blue color, which increases visual fatigue).
 +
 +===== Screen settings =====
 +
 +  * A little vocabulary to understand each other:
 +      * The **brightness** ​ corresponds to the backlighting of the display. It is the light sent to your eyes. This light is then filtered by the LCD:
 +      * The **contrast ** (and other settings) affect the LCD filter.
 +  * It is therefore necessary to modulate the **quantity** ​ and **quality** ​ of light that your eyes receive.
 +
 +  * Start by adjusting the **brightness** ​ (i.e. the backlight) so that the white of a blank page is bearable, without dazzling you. (This is usually the symbol of the **sun**.) (This reduces visual fatigue by not sending too much light into your eyes.)
 +  * Then adjust the **contrast** ​ so that it is sufficient. (This is usually the symbol of the **half-moon**). Black should be black on the screen, not grey (this reduces visual fatigue by making it easier to decipher text on the screen.)
 +
 +|  {{:​wiki:​yeux-icone-luminosite.png?​nolink&​50}} \\  //​Brightness// ​   |
 +|  {{:​wiki:​yeux-icone-contrast.png?​nolink&​50}} \\  //​Contrast// ​   |
 +
 +Settings correctly made (and unless you have a shitty screen), in the image below:
 +
 +  * Shade A should be very black, not dark grey.
 +  * You must be able to distinguish between A/B/C and X/Y/Z shades.
 +
 +{{  :​wiki:​teintes.jpg?​direct& ​ }}
 +
 +(Note that if you really have a rotten graphic card/screen combination,​ you may not be able to distinguish A/B/C and X/Y/Z. Maybe it's time to buy some new equipment.)
 +
 +===== Settings on the computer =====
 +
 +  * Avoid using fonts that are too small.
 +  * Most software allows you to zoom in on the display by holding down the **Ctrl** ​ key and using the mouse wheel (without touching the documents themselves). Have the reflex to use it.
 +  * Your eyes are not made to receive a strong light directly at all times. However, when you work on a page with a white background, that's exactly what you do (which is very different from a sheet of white paper that is not a light source). My advice:
 +      * If possible, prefer to work your texts in **white on a black background**,​ not black on a white background. A black background considerably reduces the amount of light your eyes receive. Some tips for this:
 +      * Under Windows, the f.lux software allows you to make a video inversion (in order to have a light text on a dark background for software that you cannot configure). (Be careful not to use such software if colours are important in your work.)
 +      * Some operating systems allow you to choose dark themes. (For example below under Linux:)
 +
 +{{  :​wiki:​bureau.png?​direct&​800 ​ }}
 +
 +  * **Fonts of characters:​**
 +      * If you have long texts to read on the screen, it is better to choose **sans-serif fonts** ​ (such as Verdana, Trebuchet or Arial) rather than **serif fonts** ​ (like Times New Roman). Similarly, in most browsers you can force the font to choose a stick font (better readability).
 +      * If you are a developer, give yourself a gift and stop using this abominable **Courrier font**. There are fonts specially adapted for developers that not only reduce visual fatigue, but also help to avoid errors (l/1, O/0 confusion, etc.).
 +        * Instead of //​Courrier//,​ your operating system probably already has better fonts, such as Consolas on Windows, or DejaVu Sans Mono on Linux, but there are others.
 +
 +===== Rest period =====
 +
 +  * Looking at a nearby object (the screen) at all times is tiring for your eyes.
 +  * So regularly, **look at distant objects for a few seconds** ​ (10 to 30 seconds). This allows you to rest the muscles of your eyes that are stimulated by the accommodation of nearby objects (screen). Also think about coffee breaks.
 +
 +===== Filtering softwares =====
 +
 +==== To make a long story short: ====
 +
 +These programs reduce the overall amount of blue on the screen (which is why at first you will feel that the screen is a little "​red"​).
 +
 +<​note>​**Personal opinion on these programs:​** ​ I admit, the first time I discovered this software, I found the concept somewhat mysterious. It only took me a few hours of use so that I couldn'​t do without it. It's a real relief, and I'm weighing my words. (When I cut this software, I feel like I'm being stuck with needles in my eyes because it's so unbearable.) All the people I advised him to have adopted him. Do yourself a favor: install this application too.</​note>​
 +
 +==== The scientific explanation:​ ====
 +
 +In physics, the color of a light source is used to determine its temperature. Thus a blue flame is warmer than a red flame. Similarly, we are able to calculate the temperature of a star by measuring its color (a blue star is much hotter than a yellow star). \\  \\ The term [[https://​en.wikipedia.org/​wiki/​Color_temperature|colour temperature]] can therefore be used to measure the "​heat"​ of a colour. The natural light (sun+sky in the middle of the day) is around 6500 degrees Kelvin, and that of our indoor lamps in the evening, more "​red"​ (and therefore colder), between 2400 and 3200 K. \\
 + \\
 +A temperature of 6500K therefore contains much more blue than a temperature of 3000K. \\
 + \\
 +The eye can handle 6500K during the day (and even better, protection is better), but having a 6500K screen in the eyes at night when all the surrounding lighting is at 3000K is not good. In addition to the visual fatigue it brings, it has been shown to disrupt the sleep cycle (see these articles: 1 2 3). \\
 + \\
 +Some software programs such as //​f.lux// ​ or //​RedShift// ​ reduce the color temperature of the screen by reducing the amount of blue. \\  \\ Used during the day, it already brings relief, but it is especially in the evening that these softwares bring the greatest benefit, both for visual fatigue and for sleep.
 +
 +==== The softwares ====
 +
 +These programs generally require 3 pieces of information:​
 +
 +  * The color temperature you want during the day.
 +  * The color temperature you want in the evening.
 +  * Your geographical position (latitude, longitude) in order to be able to calculate the sunrise/set times to switch from day to night mode automatically.
 +
 +  * **f.lux** ​ (recommended for Windows and OSX)
 +      * Official page: [[https://​justgetflux.com/​|https://​justgetflux.com/​]]
 +      * Download for Windows : [[https://​albakham.frama.wiki/​_media/​wiki/​flux-setup.zip|Flux pour Win$]]
 +      * Download for Mac : [[https://​albakham.frama.wiki/​_media/​wiki/​flux.zip|Flux pour Mac]]
 +
 +  * **RedShift** ​ (recommanded for Linux).
 +      * Official page : [[http://​jonls.dk/​redshift/​|http://​jonls.dk/​redshift/​]]
 +      * Note that RedShift is most likely already in the repositories of your distribution (//​redshift-gtk// ​ package).
 +
 +  * **RedMoon** ​ (recommanded for Android):
 +      * Official page : [[https://​github.com/​raatmarien/​red-moon/​blob/​HEAD/​README.md|https://​github.com/​raatmarien/​red-moon/​blob/​HEAD/​README.md]]
 +      * Note: RedMoon is paid on GooglePlay, but free on F-Droid.
 +      * You can freely download the ap here: [[https://​f-droid.org/​repo/​com.jmstudios.redmoon_25.apk|https://​f-droid.org/​repo/​com.jmstudios.redmoon_25.apk]]
 +      * **Note** ​ that most Android software **does not remove blue, but adds red**. As it stands, **no software for Android is doing its job properly**.
 +For example under Windows, here is f.lux after installation:​
 +
 +{{:​wiki:​flux-ecan-principal.png?​nolink&​}}
 +
 +Click on the //​Settings// ​ button: This is where you can set the color temperatures you want for the day and for the evening. Click on Change to tell f.lux your geographical position.
 +
 +{{  :​wiki:​f.lux_win_.png?​nolink&​}}
 +
 +Once the two temperatures have been chosen and the geographical location indicated, f.lux will automatically adjust the screen temperature according to the sunrise/set times. Feel free to lower the temperature chosen for the day.
 +
 +Personally, **I work during the day between 4000K and 4800K and in the evening in 3000K** ​ (which can be considered as a rather strong setting).
 +
 +===== Should I take special screen glasses? =====
 +
 +Most of the special "​screen"​ glasses simply filter the blue light. This is **exactly** ​ what //​f.lux// ​ or //​RedShift// ​ software does. So I consider these devices to be unnecessarily expensive... unless, of course, you do not have the freedom to install such software.
 +
 +**Note** ​ : In the case of an LCD screen backlit by LED, it is quite possible that the special glasses provide real protection (UV being particularly harmful to the eyes). It would be interesting to measure the UV emission of LCD screens... and see what wavelengths these glasses filter.
 +
 +----
 +
 +\\
 +
  
  • en/wiki/eyes-protection.txt
  • Dernière modification: 2019/03/15 01:52
  • par albakham