Robin- I've been shooting fireworks for a number of years and have two suggestions... Assuming you're using a tripod, first, try ISO 100. It will give you less noise and sharper photos. Second, stop down a bit. f/5.6 or f/8 are fine, especially if you have stuff in the foreground. No need to shoot wide open if you're on a tripod, with mirror up and cable release. And why not try some longer exposures. Like 4-6 seconds? Fourth of July is coming up. Great time to try different techniques.