f.lux is a well-known utility for desktop computers used to adjust the screen brightness depending upon what time of day it is. Most of us have used (or at least know about) eye-protectors for monitor screens. All such accessories and utilities are based on the principle that looking directly at a light source for long periods of time can be harmful for your vision in the long-run. But with smartphones getting more and more like computers, there still is no way to ease your eyes after looking at its screen for the whole day. That’s where f.lux enters the arena. It is a free Cydia tweak for your jailbroken iPhone, iPod Touch and iPad that changes the hue of the screen based on the time of day. It adds a pleasant filter to the display at night and removes it during the day. To make things even better, the f.lux app has got more than one filters that users can choose from. All of them have the same general look, and a soothing effect, but there are subtle variations as well.
The menu added by f.lux to the stock Settings app can let you configure everything related to this Cydia app, but before you do anything else, it is better if you decide upon a filter that fits your needs most appropriately. As of now, the tweak comes with a total of four filters:
You can preview each setting before you decide upon one. Whenever you choose an option, the screen will show you a preview of the effect to give you an idea as to how your iPhone will appear after sunset. Most of them might appear to be pretty similar in the preview, but when it’s really evening, you are sure to appreciate the difference having f.lux on your device really makes.
An easy one-touch toggle can be used to switch the tweak on or off. If you don’t want the tweak to alter your screen too quickly at dusk, you can choose the Long transition option and the brightness/hue will change gradually instead of in one go. It is pretty hard to capture f.lux’s full usability in words, but you can give it a try by going to the Cydia store. The tweak is present in the Big Boss repo. It works best with newer iDevices but is compatible with older ones as well.