If you are Prone with a motorcycle helmet on, you cant aim down sights. The Screen will go dark because the camera seems to be inside the helmet. Tried with m4 red dot.
- Legacy ID
Have you tried only equipping your helmet (no backpack, mask or upper body clothing) and this is still happening?
Similiar issue in http://feedback.dayzgame.com/view.php?id=5175
They had screen streaks but I had completely black screen with gas mask, military helmet and mountain backpack equipped. Couldn't test which item was causing it because of random character reset.