On a film camera the ISO has to do with the film speed on a digital sensitive you camera’s sensor is to light. The higher the ISO the more sensitive your camera is to light…so for low light settings you want to up the ISO.
Shutter speed is how fast or slow the shutter stays open and the digital sensor is exposed. The faster the shutter the less light goes into the camera. The slower the shutter the more light goes in but you’re also susceptible to shake issues.
To get a good lowlight photo you need a combo of the right shutter and ISO. That’s why you need to play with your camera to adjust for shutter speed (F rating) and ISO. Also not zooming in will help…the more you zoom the more shaking will be a factor
The other thing is lens speed. On most cameras that have a lens fixed to the camera you have a lens that’s fairly slow. If you have a camera where you can swap out lenses then you can put a ‘fast’ lens on it and alot of the problem goes away.
I have a Canon XTi and XT DSLR. These cameras I can swap out lenses and have full manual capabilities. They take some awesome shots but there’s alot to play with and it can be a pain in the you know where. Plus they weigh a ton.
I also have a Powershot SD700IS. I’m really surprised with this camera. I can’t change the shutter speed, it’s got a slow lens, but I can change the ISO and some sort of “Exp” balance. On this camera it ranges from -2 to +2. For indoor shots I have it a +2/3. The camera takes some really nice shots. I haven’t taken this one to WDW yet…but I’m really tempted to just go with this one to see what it can do.
Hopefully this was of some help. My baby kitten is playing with the keyboard so I’m going to quickly post this before he types you all some gibberish. If you have more questions please post or PM. I love taking photos and would be happy to help as much as I can!