Well.., i don't know how it came to my mind, but this is mistake. Here is simple calculation (for example): fog factor*fog(some value)=handicap. Then more fog (or less) don't influence vision itself without fog factor or fog factor=0. So don't take attention on it.

I meant to respond lol but been busy in life and time on SH 4 has been spent creating new campaign orders...which can be quite time consuming.

Yes...to keep it simple....0 means fog has no effect, number larger than 0 increases handicap. So 1.0 is a pretty strong handicap in the fog, 0.5 is somewhere in between. I have been testing and still deciding on the perfect balance for this setting. As mentioned, settings on the particular visual sensors in the AI Sensors.dat file also come in to play. So fog will handicap a merchant more than it will a escort and a capital ship. This can be used to simulate the superior optics for gunnery a escort or capital ship will have, range finders etc. Then if they have radar which acquires you, they go into "alert" mode and their visual sensors may spot your sub, then they begin to track you visually in the hierarchy of sensors used by the AI.