form_BlackLevel.xaml

<Window x:Class="Free_Gamma.form_BlackLevel"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Free_Gamma"
        mc:Ignorable="d"
        Title="Black Level Test" MinHeight="450" MinWidth="800" Background="Black" TextOptions.TextFormattingMode="Ideal">
     <StackPanel x:Name="pnl_1" Margin="10">
          <TextBlock Text="Set your screen hardware brightness to maximum" Foreground="#FFA6A6A6" HorizontalAlignment="Center" VerticalAlignment="Top" FontSize="14" />
          <TextBlock Text="The darker you see the black area on this window, the better your screen is." Foreground="#FFA6A6A6" HorizontalAlignment="Center" VerticalAlignment="Top" FontSize="14" />
        <TextBlock Text="This is basiclly for comparision between different monitors" Foreground="#FFA6A6A6" HorizontalAlignment="Center" VerticalAlignment="Top" FontSize="14" />
     </StackPanel>
</Window>