To do this you have to use the Mod Exec. It doesn't work with the regular Exec.
1. Open the console with the tilde key.
2. Type in " bool gui "
3. Press enter
4. Exit the console.
There are things you need the Hud for; Talking to NPCS, Teleporting, Inventories, Etc. But as you can see from the Video, this console command is well worth using.
NOTE: In the video I type in the console command a second time, to restore the hud. This is not necessary. With the console open, the up key will bring the command up again.
For more info on console commands get the " Release Executable Readme File.zip " posted by Ulyss on the Siege the Day Website.
Siegetheday.org
Note: If you just want a screen shot without the Hud, hold hold down Ctrl when you press Print Screen.