There's been a lot of questions about ND filters lately...
Shutter speed is simply slowed by the number of stops of the ND filter. So an ND 6 stop will slow a shutter down by 6 f-stops. So if you're getting 1/60 without an ND, then with the ND you'll get a shutter speed of 1 second (1/60 * 2 ^ 6).
The problem is knowing how many f-stops your ND filter is. A 6 stop could be refrered to as an ND64, ND 6-stop or ND 1.8.
Quote: Can someone please give me an example of what would happen to the shutter speed if you say too a photo at f10 1/100 if you then put on a ND4 filter and left the aperture the same and took the same photo.
I'm going to assume this is a 2 stop filter, so your shutter speed will be 1/25 (1/100->1/50 for 1 stop -> 1/25 for 2 stops). There's very little use for a 2-stop ND filter to be honest, a CPL will serve as one anyway.