Whichever camera you use, a lower ISO (light sensitivity) setting will give sharper images with better colour and less noise. So start with a setting such as ISO100 or ISO125 and then adjust your aperture and shutter speed to get a good exposure.
If you're shooting handheld, start with the slowest shutter speed
you can use without introducing unacceptable blurring caused by camera shake or the motion of the fireworks. A shutter speed of around 1/10 sec often works well – fast enough to freeze the motion
of the fireworks, but long enough to capture their light. When using a camera on a tripod, you can use a much slower speed, such as one or two seconds, as your starting point.
When you want to retain some sharpness throughout the scene, start with an aperture setting around f/8. If you need to let more light in but can't use a slower shutter speed without blurring, then you can try widening the aperture to f/5.6 or f/4 – but the wider you make the aperture (that is, the smaller the f-number), the narrower the depth of field
also becomes, meaning that less of the scene is in sharp focus.
It may take some trial and error to find the right balance of shutter speed to capture the detail you want as sharply as you want, combined with an aperture that gives a good exposure and the depth of field you want. If you can't get well-exposed, blur-free results using aperture and shutter speed, then try adjusting the ISO. Cameras with larger sensors – such as full-frame mirrorless cameras like the EOS RP
or EOS R6
– offer better high-ISO performance and will give the best results, but it's still a good rule of thumb to keep ISO low and increase it only if you need to.