The ISO setting is your camera's sensitivity to light. So, if you have your camera phone (or any camera) set to 100iso, a daylight setting, and you go inside a house and take a photo, you will get camera shake. You would need to use 400ISO or 800 ISO depending on how much light is in the room. Image stabilisation keeps the camera steady, therefore overriding your ISO. So if you want to specify ISO settings, you have to understand light and be alert every time you want to take a photo. I used analogue cameras for years, so I guess I'm used to this.