Hair - strange white light

i have

  1. plane with hair shader and Shadow Two Sided - on

  2. spot light and camera on side “A”

  3. second camera on side “B”

side “A” looks normal.

side “B” have strange white light. Why? How to fix it? **I expect Side “B” all dark. **

side “A”

side “B”

aditinal examples with strange white

318513-paragonhairsbug.png