whenever running player full screen it automatic brighten the screen .. WHY??

whenever running player full screen it automatic brighten the screen .. WHY??
how to disable it?>>

MPC-HC (64-bit)
---------------

Build information:
   Version:            1.8.7 (1cec1bbe9)
   Compiler:           MSVC v19.16.27032.01
   Build date:         Jul 17 2019

LAV Filters:
   LAV Splitter:       0.74.1.22
   LAV Video:          0.74.1.22
   LAV Audio:          0.74.1.22
   FFmpeg compiler:    MinGW-w64 GCC 8.3.0

Operating system:
   Name:               Windows NT 6.1 (build 7601, Service Pack 1)
   Version:            6.1 (64-bit)

Hardware:
   CPU:                Intel(R) Core(TM) i5-2450M CPU @ 2.50GHz
   GPU:                Intel(R) HD Graphics Family (driver version: 8.15.10.2291)

It is not the player that is doing that but the Intel graphics driver.

Here you can find instructions on how to fix it:
https://superuser.com/questions/994443/brightness-changes-while-adaptive-brightness-is-disabled-in-windows-8-1-10-wit

then why its not happening with vlc wmp or any other player i have.. happening only with mpc

also changed gpu but same thing occurring...

MPC-HC (64-bit)
---------------

Build information:
Version: 1.8.7 (1cec1bbe9)
Compiler: MSVC v19.16.27032.01
Build date: Jul 17 2019

LAV Filters:
LAV Splitter: 0.74.1.22
LAV Video: 0.74.1.22
LAV Audio: 0.74.1.22
FFmpeg compiler: MinGW-w64 GCC 8.3.0

Operating system:
Name: Windows NT 6.1 (build 7601, Service Pack 1)
Version: 6.1 (64-bit)

Hardware:
CPU: Intel(R) Core(TM) i5-2450M CPU @ 2.50GHz
GPU: NVIDIA GeForce GT 630M (driver version: 8.17.12.8580)

It is not the player that is doing it!!! Different players use different methods of rendering which can cause the system to behave differently.

Your screen is connected to the Intel GPU, so even when you use the NVIDIA GPU, the Intel one is active as well. So you really should look at the setting in the Intel control panel.

Another possible cause for brightness changes is that the power profile changes. For example Bitdefender can do that:
https://superuser.com/questions/1140118/brightness-changes-watching-fullscreen-movie-with-subtitles

yeah it changes power profile when go full screen on MPC and when exit it resumes entertainment mode.. but why on mpc why not on VLC and WMP.. i m using avast premium security..

There is probably a program installed on your laptop that switches the power plan based on which program is started. For example Asus has a program called Power4gear. Why it switches profiles, I do not know, maybe it thinks a game is running.

Remove that tool. Or change it settings. Or use same brightness in the two power profiles.