Shutter speed controls background exposure? Usually ...
Something I kick against when I try to teach others about flash photography, is the use of short-cut phrases. Those axioms that are supposed to help the understanding of how to mix flash with ambient light, can often mislead you since they don't give you all the information.
Two of those phrases were recently discussed here:
aperture controls flash exposure,
shutter speed controls available light.
These are merely reductions of the way that shutter speed, aperture and ISO inter-relate with available light and Read more inside...
Flash exposure is controlled by aperture ... but only for manual flash
Quite often the short-hand descriptions of the fundamentals of flash photography become misleading 'facts'. I frequently see the following statements repeated on the various photography forums and in questions that are emailed to me:
flash is controlled by aperture
shutter speed controls ambient light.
(This is sometimes twisted around to a completely misleading version:
ambient light is only controlled by the shutter speed.)
Even though these descriptions are half-right, they are also half-wrong Read more inside...
Generally, you wouldn't use flash to photography fireworks. But when you have someone in the foreground, then it becomes useful to have your subject lit up with flash, to balance them with the background (the fireworks display.)
Photographing people with fireworks in the background, is just an application of the technique known as dragging the shutter. I had the couple in an area where there wasn't much ambient light, so that I could light them mostly with flash. The strobe was a Quantum T2 with an umbrella, used in manual.
My flash exposure Read more inside...