How much difference are there? I like taking pictures w/o flash sometimes... I think the whole... "flash-in-your-face" thing really doesn't capture the moment... I had a camera that was at ISO400, I just returned it at Costco (thank God for Costco), I was gonna turn around and buy another one... but decided to do a little research first...

(by the way... if it matters, I'm just shopping around for point and shoot cameras)

 

The ISO's you listed are one stop apart. Keep in mind that ISO 400 and above on most point and shoot cameras isn't going to be very good. You'll get noisy images.

 

the crud but reasonably accurate answer is:as you multiply the ISO by 2, you halve the shutter speed. You will also crank up color/shadow noise, and probably also lose detail due to noise reduction.

Most point and shoots have pretty horrendous high ISOs. Only the recent Fuji Point and shoots have decent high ISOs.

 

I wouldn't use anything above ISO 400 on a P&S camera. The Fuji F30 is better than most at ISO 800, but I still would only use it if I had no other way to get the shot.

Perhaps you could look at a camera with image stabilization. That will let you use longer shutter speeds without getting a shaky picture. It doesn't help if your subject is moving, but it will let you take hand-held shots in darker conditions than you normally would. A tripod would also help if you're trying to do night photography.