On unlocking the device with Touch ID a burst of white light is produced from the Top Left/Right corners of the screen.
It happens when more than two folders are created i.e three/four folders each having some applications and the phone is locked while on the same screen.
If no folder or maximum two folders are created then no such burst is produced when unlocking with Touch ID.
1. Configure Touch ID
2. Use Black/Dark wallpaper on Home & Lock Screen.
3. Create minimum four folders either on the home screen or the second having some applications in each.
4. Being on Home Screen lock the phone.
5. Unlock with Touch ID and a Burst of White Light will appear on Top Left/Right Corner.
6. Now move/drag two of the folders to the other second page.
7. Go back to Home Screen and lock the phone.
8. Unlock with Touch ID and there is no Burst of White Light.
OR
Repeat step 1 and 2 as listed above.
1. Go to the second screen (after home screen) and create three or four folders with applications in it.
2. Lock the iPhone while on the same screen.
3. Unlock with Touch ID and there is a Burst of White Light.
4. Now drag or remove the folders with only two left.
5. Lock the iPhone while on the same screen.
6. Unlock with Touch ID and there is no Burst of White Light.
NOTE: If iPhone is LOCKED and UNLOCKED when on the screen with no folders NO WHITE BURST is there.
Burst of White Light when apps added to a folder and unlocked with Touch ID. This is noticed since the update iOS 7.0.6 [11B651]
The burst of light on iPhone 5s is easily recognized but on iPhone 6 its for a fraction of a second. Not checked on iPhone 6+.