os.path.join doubt

[harryos]

In windows ,I tried this

p1 = "C:\Users\me\Documents"
p2 = "..\Pictures\images\my.jpg"

print os.path.join(p1,p2)
This gives
'C:\\Users\\me\\Documents\\..\\Pictures\\images\\my.jpg'

I expected I would get
'C:\\Users\\me\\Pictures\\images\\my.jpg'

I thought os.path.join would join the paths more intelligently..Any
idea why this happens ?
harry