I have a Samsung Grand Neo Plus. That phone misses the brightness sensor but has the front facing camera.
Using Lux Lite (the free version) or Lux (the full version) application it’s possible to configure the front facing camera as brightness sensor.
After installing it, the application uses the light conditions captured from the front camera to change the phone brightness. I set the brightness update on unlocking.
Another useful thing is the possibility to increase the brightness shaking the phone. In Settings >> Brightness >> Shake to increase brightness. It works being in the lock screen.
If the brightness is too high or low it’s possible to customize the regulations opening the application, modifying the brightness and clicking on the chains symbol to link the ambient light values to the display brightness.
For my Grand Neo Plus I linked the following values: