One of the strengths of the iPhone display is its brightness. This is great during the day, when you want to be able to see the screen as easily as possible. Night time is a different story. We've all seen smartphone users' faces illuminated in a bright, blue glow at night. Not only does it look strange, but this light can actually interfere with the body falling asleep.
The developers of f.lux have a different idea, iPhone display lighting colors that actually match the time of day. They have released similar software for desktop computers, which automatically adjusts the color of your display. F.lux is smart enough to know when sunset occurs based on your location, so your iPhone adjusts without intervention.
Once the f.lux tweak is installed, simply run the f.lux app to determine your location. This is how f.lux knows when sunset occurs in your area. You can then navigate to Settings -> f.lux to let the tweak know what kind of lighting you are interested in matching at night.
Night time choices include Candle, Incandescent, Halogen and Fluorescent. Daytime lighting selections include Halogen, Fluorescent, Midday Sun and Normal. Normal will keep your iPhone screen looking like you're used to, with more blue (6500K). F.lux can be disabled at any time just in case you're doing color-sensitive work such as working on photos.With f.lux installed, you can rest easier at night knowing your iPhone isn't simulating bright sunlight when you're trying to rest. It's also good to know you won't be illuminated so brightly in public just because you need to send a text after sunset. After all, the built-in ambient light sensor can adjust brightness, but not the color temperature.
F.lux 0.985 can be installed for free on Cydia from the Cydia/Telesphoreo repository. Check here for instructions on how to jailbreak iOS 6.x with evasi0n. You can also find out how to purchase and install Cydia tweaks with this guide.