gimme some feedback pls if u can 
Are you sure it is 1/100000? Did you compare for example with 1/50000?
Such fast shutter doesn't work for my S2. Take a look at my test results below:
Mess in my room
M, ISO 100, t=15s, f/8 (+nd3x)
Exposure Time
1) set in canon 15 - measured 15 - makernotes 16 - OK
2) set in chdk 15 - measured 14 - makernotes 15 - OK
3) set in chdk 30 - measured 28 - makernotes 30 - OK
4) set in chdk 60 - measured 56 - makernotes 60 - OK
5) set in chdk 90 - measured 94 - makernotes 88,6 - bit lighter than 60s - (it's 65s)
6) set in chdk 120 - measured 94 - makernotes 119,9 - same as 90s (it's 65s)
7) set in chdk 180 - measured 94 - makernotes 177,1 - same as 90s (it's 65s)
lightbulb 75 W
M, ISO 100, t=1/1600s, f/3.5, z432, focus 1.7 m
14) 1/100000 - same as 1/10000
15) 1/50000 - same as 1/10000
16) 1/20000 - same as 1/10000
17) 1/10000
18) 1/5000
19) 1/2000
20) 1/1600
21) 1/1600
lightbulb 75 W
M, ISO 400, t=1/2500s, f/8, z432, focus 1.7 m
22) set in chdk 1/2500 - makernotes 1/2489
23) set in chdk 1/5000 - makernotes 1/4978
24) set in chdk 1/10000 - makernotes 1/9955
25) set in chdk 1/20000 - makernotes 1/19911
26) set in chdk 1/50000 - makernotes 1/49452 - bit lighter than 1/20000
27) set in chdk 1/100000 - makernotes 1/98905 - same as 1/50000 (bit lighter than 1/20000)
