I am sure this might spark some jokes about ugly faces but here is what happended to me yesterday.
I was out for a walk in a wood that I have access to, hoping to spot a buck. I was walking along a track when I spotted a roe not more than 20-25 metres away. The animal's head was behind a large tree so it could not see me. Thinking that the deer would only need to take one step forward and I would be in full view as I was in the middle of the track, I froze and lifted the bins to my eyes. I did this hoping to catch a quick close up glimpse of the animal as I was certain it would disappear instantly when it saw me.
Well she (it was a young doe) walked into the middle of the track, had a good look at me and carried on browsing! I didn't move and kept the bins over my face and the doe carried on munching and looking in my direction every now and then. Then I decided to test what would happen if I exposed my face. So I gently lowered the bins while she had her head down. A few seconds later she lifted here head, had one look at me and legged it in the opposite direction!
So when I go stalking I will carry on wearing my camo face mask and gloves. Covering the white of the face does make a difference!