Shooting fireworks is interesting, in my opinion, from the standpoint that the primary variable relative to exposure is the length of exposure, more so than ISO or aperture. Shutter speed determines the ‘look’ of the firework. Are you looking for a vibrant, static, flower-looking shot, or lights that trail off like in this example? One has to understand that although you’re shooting at nighttime, you are not shooting in low-light conditions when shooting against a dark sky. The fireworks themselves provide their own illumination and are plenty bright at a considerable range of exposure, in my experience. The caveat to this is when shooting against a city skyline. In that case, expose for the skyline at whatever shutter speed you choose and let the let the fireworks take care of themselves. This particular July 4, I shot with a constant 10 second shutter at ISO 100, only making aperture adjustments from time to time. I found that I didn’t have any significant overexposure until I went wider than f-9 or so. This was also a slower, tele-lens rated 5.6. The camera is obviously on a tripod, and I reclined in the grass with a handheld remote, shooting constantly so I could also relax and enjoy the show. If anyone would like to share their own fireworks experience/info, please comment.