From Skyrim and Oblivion that brightness and the weight of your armor have a big influence on how quickly you were spotted by an enemy or a mere house inhabitant - especially while you were sneaking.
However, in Fallout 4 I did not notice much consistency during sneaking. Examples:
- My armor's weight was often different → no difference recognized.
- Light source of the surrounding was often different → no difference recognized.
- My crucial experience which led me to create this question: The Torchlight, which is activatable with long pressing of TAB, seems to have no influence at all. In some cases there was just a corridor, I had the torchlight turned on, but the enemies (mainly raiders or looters, humans by any means with some basic intelligence) didn't find or see me although they recognized that someone entered the area.
The only thing which clearly seems to have an influence is opening fire: Without a silencer the enemies are able to spot you much more quickly. That's the reason why I primarily use a silenced pistol.
So, those are my experiences. Might any friend of sneaking out there have facts for those experiences? Does the companion also take a role here maybe? Or am I really true and there wasn't much effort put into the sneaking/spotting system, what I can't imagine?