F.lux

{{Short description|Program to adjust a display to reduce eye strain}}

{{About|the computer display-controlling software||Flux (disambiguation)}}

{{Infobox software

| name = f.lux

| logo = F.lux logo.svg

| screenshot = F.lux on computer screeen stitched photo.jpg

| caption = Two photos of a screen stitched together, f.lux disabled (on the left), and f.lux's default settings (on the right)

| author = Michael Herf, Lorna Herf

| developer = F.lux Software LLC

| released = {{Start date and age|2009|02}}

| latest release version = Windows: v4.137
macOS: 41.5
iOS: 0.9986{{Cite web|url = https://justgetflux.com/cydia/|title = f.lux for iOS|work = f.lux|accessdate = October 13, 2018}}

| operating system = Windows, macOS, Linux, Android, iOS

| language = English

| license = Freeware

| website = {{URL|https://justgetflux.com}}

}}

f.lux (pronounced "flux") is a cross-platform computer program that adjusts a display's color temperature according to location and time of day, offering functional respite for the eyes. The program is designed to reduce eye strain during night-time use, helping to reduce disruption of sleep patterns.{{cite web|last1 = Zukerman|first1 = Erez|title = Review: f.lux makes your computer usable at night|url = https://www.pcworld.com/article/2056895/review-f-lux-makes-your-computer-usable-at-night.html|accessdate = 3 March 2015|website = PC World|date = October 31, 2013}}{{cite web|last1 = Tanous|first1 = Jim|title = Save Your Eyes and Improve Your Sleep with f.lux for OS X and Windows|url = http://www.tekrevue.com/f-lux-review/|accessdate = January 15, 2016|website = TekRevue|date = October 15, 2014|archive-date = October 17, 2014|archive-url = https://web.archive.org/web/20141017175819/http://www.tekrevue.com/f-lux-review/|url-status = dead}}

Functionality

File:F.lux Darkroom mode.jpg

On installation, the user can choose a location based on geographic coordinates, a ZIP code, or the name of a location. The program then automatically calibrates the device display's color temperature to account for time of day, based on sunrise and sunset at the chosen location. At sunset, it will gradually change the color temperature to a warmer color and restore the original color at sunrise.

f.lux offers a variety of color profiles and pre-defined temperature values, modifying program behaviour for specific programs or activities; including a mode for film watching, decreasing red tinge (for 2.5 hours), and a darkroom mode that does not affect night-adapted vision. Times can be inverted on f.lux for PC to provide warm lighting during the daytime (for people who work at night).{{cite web |url=https://justgetflux.com/faq.html |title=f.lux: F.A.Q. - I work nights. How do I flip the day and night settings? |website=justgetflux.com|date= |author= |accessdate= 31 October 2016}} The program can control Philips Hue LED lighting, so that the color temperature of house lights follows f.lux's settings.{{cite web |url=https://justgetflux.com/news/pages/bigupdate/ |title=f.lux has been updated to a new version |website=justgetflux.com|date=|author= |accessdate= 31 October 2016}}

Platforms

The program is available for Microsoft Windows, macOS and Linux (except for Ubuntu 18.04 LTS). It is also available for Apple iOS devices, although it requires the device to be jailbroken.{{cite web|url=http://www.howtogeek.com/199303/reduce-eye-strain-and-get-better-sleep-by-using-f.lux-on-your-computer/|title=Reduce Eye Strain and Get Better Sleep by Using f.lux on Your Computer|last1=Hoffman|first1=Chris|date=October 23, 2014|website=How-To Geek|accessdate=January 15, 2016}} Apple has not allowed the application in its App Store due to its use of restricted developer tools.{{Cite news|url=https://www.theguardian.com/technology/2016/jan/12/apple-good-sleep-new-iphone-feature-night-shift|title=Apple promises a good night's sleep with new iPhone feature|last=Hern|first=Alex|date=January 12, 2016|newspaper=The Guardian|access-date=January 20, 2016}} The developer briefly hosted an Xcode project on GitHub, allowing iOS 9 users to sideload the application onto their devices, but retracted it at the request of Apple.{{Cite web|url=https://techcrunch.com/2015/11/12/f-uxd-apple-says-screen-brightness-app-violates-developer-agreement/|title=F.uxd: Apple Says Screen Brightness App Violates Developer Agreement|last=Tepper|first=Fitz|date=November 12, 2015|website=TechCrunch|access-date=January 15, 2016}} Following Apple's announcement of a similar function, called Night Shift, in iOS 9.3, the developer called upon Apple to provide developer tools and to allow their application into the App Store.{{Cite web|url=https://techcrunch.com/2016/01/15/f-lux-asks-apple-to-let-its-screen-brightness-app-back-into-app-store/|title=F.lux Asks Apple To Let Its Screen Color Adjustment App Back Into App Store|last=Perez|first=Sarah|date=January 15, 2016|website=TechCrunch|access-date=January 20, 2016}} A preview version for Google's Android system is available.{{Cite web|url=https://justgetflux.com/|title=f.lux Home Page|website=f.lux|access-date=September 21, 2016}}

Efficacy

Reducing exposure to bright (1000 lux) blue lights at night time was linked to increased melatonin secretion in a 1996 study{{Cite journal|title = Effects of Lights of Different Colour Temperature on the Nocturnal Changes in Core Temperature and Melatonin in Humans|date = 1996|journal = Journal of Physiological Anthropology|last2 = Hiromi|first1 = Morita|last1 = Takeshi|first2 = Tokura|issue = 5|volume = 15|pages = 243–6|doi = 10.2114/jpa.15.243|pmid=8979406|doi-access = free}} but a 2018 study showed that changing the spectral composition of self-luminous displays without changing their brightness settings may be insufficient for preventing impacts on melatonin suppression.{{cite journal |last1=Nagare |first1=R |last2=Plitnick |first2=B |last3=Figueiro |first3=Mg |date=May 2019 |title=Does the iPad Night Shift mode reduce melatonin suppression? |url=https://www.lrc.rpi.edu/resources/newsroom/pr_story.asp?id=383 |journal=Lighting Research & Technology |volume=51 |issue=3 |pages=373–383 |doi=10.1177/1477153517748189 |pmc=6561503 |pmid=31191118 |access-date=2021-09-16 |archive-date=2022-01-15 |archive-url=https://web.archive.org/web/20220115220031/https://www.lrc.rpi.edu/resources/newsroom/pr_story.asp?id=383 |url-status=dead }}

f.lux proponents hypothesize that altering the color temperature of a display to reduce the prominence of white–blue light at night will improve the effectiveness of sleep. Although the developer provides a list of relevant research on their website, the program itself has not been scientifically tested to determine its efficacy, and the equivalent Apple program, Night Shift, was shown to have no effect on sleep outcomes (sleep latency, duration, efficiency and wake after sleep onset) in a 2021 study on 167 college undergraduates.{{cite journal |last1=Duraccio |first1=Kara M. |last2=Zaugg |first2=Kelsey K. |last3=Blackburn |first3=Robyn C. |last4=Jensen |first4=Chad D. |title=Does iPhone night shift mitigate negative effects of smartphone use on sleep outcomes in emerging adults? |journal=Sleep Health |date=August 2021 |volume=7 |issue=4 |pages=478–484 |doi=10.1016/j.sleh.2021.03.005 |pmid=33867308 |s2cid=233299395 |url=https://news.byu.edu/intellect/is-night-shift-really-helping-you-sleep-better}} f.lux has been widely and positively reviewed by technology journalists, bloggers, and users.