Hi nwhite654 !!
This filter optician periscopes, and included it button next to the compass at the bottom right.

If you do not plan to in the future to use a filter, the menu_1024_768.ini block [G3F I321] before the line Mat 0 = data / menu / Gui / filter.tga put ;. Should look like this:
[G3F I321]
Name = Optic Filter
Type = 1030
ItemID = 0x3F039903
ParentID = 0x3F1C0000
Pos = -1388,920,850,850
Display = 0
Materials = 1
; Mat 0 = data / menu / Gui / filter.tga
MatFlags = 0x29
TexFmt = 0x9
Good luck
++Ahnenerbe++