Difference between flash shutter speed and flash synchronization speed

I don't know what you mean by flash shutter speed. Generally speaking, cameras have a maximum flash synchronization speed. What does that mean? In other words, when you use a flash, the camera you use can only be exposed normally within this shutter speed. If it is higher than this shutter speed, it will not be exposed normally. Generally speaking, there will be shielding effect, that is, local blackening. This is because the shutter of an ordinary SLR camera is an exposure process that moves from left to right or up and down. In addition, the current high-end flash will have high-speed synchronization function, but at this time, the indicators of the flash will drop sharply, that is, the light output will drop sharply.

Generally, the flash synchronization of SLR cameras is between a few tenths of a second and a few hundredths of a second, such as 1/60s,1/60s, 1/250s, etc. But some cameras, such as paraxial cameras or some medium format cameras, use an inter-mirror shutter, that is, its shutter is directly built into the lens. Generally, this camera can flash normally at all shutter speeds.

Finally, in the dark environment, when your flash plays a major role, in the case of normal synchronization, the exposure only depends on the index of your flash and the distance between the flash and the object, regardless of the shutter speed.