This post reviews f.lux, a jailbreak tweak that automatically warms the tint of your jailbroken iPhone, iPad (Mini, Air), or iPod Touch’s display at night making your device easier on your eyes.

Have you ever noticed that your iPhone, iPad, or iPod Touch’s display is tough to look at at night? LCD displays tend to have a blue hue to them, which can be really harsh at night. In fact, since natural sunlight is on the blue end of the spectrum it could also be argued that staring at a bright blue screen at night could not be good for your body’s sleep/wake rhythms. f.lux is a free tweak available for jailbroken devices that takes care of these problems by gradually warming the tint of your device’s display as nighttime approaches. In this post, I’ll give you an in-depth look at this f.lux and show you why I’ve been using it for years and why it’s always one of the first tweaks I install on a newly jailbroken device.

Using f.lux – For being so useful, f.lux is an incredibly simple tweak. One of the reasons I love using f.lux is its “set it and forget it” approach. Once the tweak is installed and configured to my liking I almost never remember that it’s even there. Often it’s not until I use someone else’s iPhone at night and am blinded that I remember that f.lux is installed. This is because f.lux runs in the background and works automatically.

When using f.lux, your device’s screen will function normally during the day. The tweak uses your location to establish your time zone and intelligently recognizes when the sun will set and rise. As nighttime approaches, your device’s display will slowly (nearly imperceptibly) begin to warm up. By the time the sun has set and it is dark outside, the display will be fully warmed up to the level you have indicated in the settings. Check out the screenshots below for an approximation example of what this progression looks like. (f.lux’s changes don’t show up when taking screenshots, so I had to simply warm up the screenshots in Lightroom. It’s not perfect but it gets the idea across.)

Then, as the sunrise approaches and daylight begins to set back in, f.lux will cause the reverse to happen. I’m seldom up early enough to witness this, but if you have a job that starts before sunrise this gradual cooling down of your display’s tint could come in really handy.

Settings – Getting f.lux working correctly is probably the most important thing with this tweak. The good news is that f.lux is pretty easy to set up and get working.

The first thing to note about setting up f.lux is that there are two places you can do it: the f.lux app on your device’s home screen or in the f.lux section of the Settings app. I recommend configuring most of the tweak’s settings via the Settings app, though it doesn’t hurt to pop the app open afterward to make sure everything looks good there too.

In the Settings app there are four different sections to adjust. The first two are listed under the Choose Lighting heading and offer choices for At Night and Daytime. Tapping on one of the At Night section allows you to choose what level your display will warm to at night. Options range from Fluorescent (coolest) to Candle (warmest). Under Daytime you can select the baseline display temperature that will show during the day. Options range from Normal (coolest) to Halogen (warmest). Once you have these two temperatures selected, f.lux is pretty much ready to go. The next setting allows you to toggle on or off long transition that takes place as the sun rises or sets and opt for a quicker transition between cool and warm. The final available setting is a killswitch that allows you to easily disable f.lux if you’re doing color sensitive work. I have used this toggle on occasion when I’m editing photos or watching videos on my device when I want my display to show color as accurately as possible.

The f.lux app gives you finer control over your display by employing sliders to control its nighttime and daytime temperatures. Below this, the app displays what time the sun has/will set or rise and the current temperature of the display. It also includes a Preview button and a button that allows you to Disable f.lux for a while. 

There is also a Location tab that allows you to see your device’s current location on a map so that you can ensure that f.lux is calculating the sunrise and sunset correctly.

As I said before, I tend to opt for using mostly the Settings app to configure f.lux. It’s easier to use and gets the job done nicely.

Conclusion – As I mentioned before, f.lux is one of my favorite jailbreak tweaks. In fact, my iPhone and iPad don’t really feel complete without it. f.lux has been around for years and has stood the test of time as an essential addition to the stock iOS experience. It is a great example of how a jailbreak tweak can elevate the experience of using iOS above and beyond the features Apple has included by default. And you can’t beat the price: f.lux is available for free on the Cydia store. Find it and install it on the search tab.

I would say that f.lux alone is reason enough to jailbreak iOS as it is very low maintenance, works flawlessly, and dramatically improves the experience of using your iPhone, iPad, or iPod Touch at night. For more information on jailbreaking, please see our series on the subject starting here. To find out how to jailbreak iOS 7, click here.

f.lux is also available on several other platforms including Mac OS X, Windows, and Linux. I highly recommend the Mac OS X version as well. Get more info on f.lux’s website here.