This is an augmentation of Timeslips tweaks, it adds pixel shaders (see below)
Installation
1) Install Timeslips Sfall Tweaks
2) Download: http://www.persiist.com/present/dedither/global.fx
3) Just place this at \data\shaders under your fallout installation and set "Mode=4" and "GlobalShaderMode=3" in ddraw.ini
4) Enjoy
NOTE: Requires video card capable of rendering shadermodel 2.0 (ie. any card claiming to be directx9.0 compatible, or newer)