Iphone 4 how does auto brightness work

Learn more Brightness can affect battery life. To maximize battery life , let auto-brightness adjust your display or dim your screen. Use Night Shift to adjust the colors of your display.

Learn what to do if your display won't turn on or if you have other screen issues. Published Date: March 30, Yes No. Character limit: Maximum character limit is We'll explain how to automatically implement all of this functionality below. Figure 1. The measured Screen Brightness for various measured Ambient Brightness levels. The manually determined optimum brightness settings are the black data points with their trend line. Circles are the data points. The dashed lines show a wide range of alternative brightness relations.

The graph is linear from 0 to 2, lux and then jumps in steps to 10, and , lux. The labels from Pitch Black to Direct Sunlight roughly identify the lux levels associated with them. When Auto-Brightness is turned On the Brightness slider adjusts the Auto behavior to allow consumers in principle to set their own individual screen brightness preferences for ambient light.

The results are plotted as the colored lines in Figure 1 — the circles are the measured data values. None of the Auto Brightness settings even remotely approaches the desired behavior discussed above. It certainly looks as if no one at Apple ever bothered to set or check Auto-Brightness for useful performance, which is why there are lots of user comments questioning how it works on the web… This is Brightnessgate for the iPhone.

At 2, lux, where just about everyone will want the display operating at maximum brightness, Auto-Brightness sets it to only 60 percent of maximum, so Auto-Brightness is throwing away 40 percent of the precious brightness needed for screen visibility.

And at 10, lux, which is full daylight, the screen brightness is still below 90 percent of maximum. The iPhone 4 Auto-Brightness performs in a bizarre fashion where it typically makes the screen too bright at lower indoor ambient light levels which is important for saving battery power and too dim at higher outdoor levels which is important for screen readability — it's always wrong, usable but very inefficient and wasteful.

But Brightnessgate for the iPhone gets even worse. One behavior of the iPhone 4 Auto-Brightness that is a serious operational error or bug is that it locks onto the brightest ambient light sensor value that it has measured at any point starting from the time it was turned on, and then continues to use that highest value indefinitely to set the screen brightness until the display turns off — either by cycling through sleep mode or full power off.

This means that the screen brightness is frequently set too high, which wastes power and can cause eye strain if you move to lower ambient light levels. Auto-Brightness should always follow the current ambient light level with appropriate time averaging and filtering. Apple should correct this with a software update.

To easily verify this behavior with your own iPhone turn On Auto-Brightness under Settings and set the Brightness slider near the middle of its range. Go to a very dark location. Note the screen brightness in the dark. Now take the phone to a very bright outdoor location such as in direct sunlight then go back with the display on to your original dark location and monitor the screen brightness.

The display will remain at very high brightness indefinitely until the iPhone enters sleep mode again or runs out of battery. What's even more shocking is that Brightnessgate is even worse on Android phones. Figure 2. The Manual Optimum relation and other elements are the same as in Figure 1.

There are currently a large number smartphones running Google's Android OS, and all of the models that we have looked at appear to work in the same way. There is a slider for manual adjustment of screen brightness, but when Automatic Brightness is enabled the slider disappears and there aren't any user settings or preference adjustments unlike the iPhone 4 — you get whatever screen brightness settings Android and the smartphone manufacturers have pre-programmed into them.

Unfortunately, those Automatic Brightness settings are incredibly primitive and crude — on the Samsung Galaxy S and HTC Desire that we lab tested Automatic Brightness produces only four fixed screen brightness levels when the ambient lighting changes from pitch black all the way up to direct sunlight, with each manufacturer setting their own breakpoints as shown in Figure 2. For this reason alone, Auto Brightness is effectively useless for Android.

But Brightnessgate on Android gets even worse. Both of the Android phones we lab tested have their own Auto Brightness operational errors or bugs. Step 5. Turn the lights on and your iPhone and iPad will use the pitch black brightness as a reference point for changing lighting conditions.

Surprisingly, this trick works on a lot of Android devices as well, but your mileage may vary. For me, it has been a bulletproof method calibrating Auto Brightness feature on the iPhone and iPad. If none of the methods work, then there is a chance that the ambient light sensor on your device might be broken. You'll need more than calibration to fix it. Therefore it's a good idea to take your device in for an expert hardware diagnosis and repair if needed.

By Uzair Ghani.