Lubuntu – How to Fix Brightness Control Issues on Laptop

I am trying to change the brightness of my laptop using xrandr, but I get this error.
Here's the segment:

janreggie@janreggie-T100TA:~$ xrandr
Screen 0: minimum 8 x 8, current 1368 x 768, maximum 32767 x 32767
DSI1 connected primary 1368x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1368x768      60.10*+
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
janreggie@janreggie-T100TA:~$ xrandr --output DSI1 --set backlight 10
X Error of failed request:  BadName (named color or font does not exist)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  11 (RRQueryOutputProperty)
  Serial number of failed request:  34
  Current serial number in output stream:  34

What am I doing wrong? Any help would be appreciated.

My laptop is an ASUS Transformer T100TA, installed per Lubuntu 15.10 ISO.