Flash Synchronization is the firing of a flash unit with the end of the closure of shutter, ensuring closure after full duration of the flash when it was opened. Two relevant articles with this article on Flash Synchronization are – Flash Unit of Digital Camera and Hot Shoe. Almost all relevant basic articles on Digital Photography are already discussed, if you find difficulty with any terminology in this article, please use the Search function for proper understanding.
Methods of  Flash Synchronization in Digital Photography
Traditionally, there are three different methods of flash synchronization :
- M-synchronization
- X-sync
- FP-sync
This distinction is independent of the transmission of the signal. It is merely designations for standardized procedures and technical requirements or conditions. They are used in both wired and wireless methods of Flash Synchronization.
Modern flash units of popular camera simplify Flash Synchronization by numerous automation features and enhancements such as wireless flash control, second curtain and stroboscopic flashes. It is possible to use shutter speeds that are much shorter than the Flash Synchronization speed. This extremely short times, gives a fill-in Flash Synchronization in almost every situation possible.
If the Flash Synchronization socket used to connect studio flash units, no automatic functions of flash units can be used as they can not transmit additional info to control. The FP-synchronization can not be used. Through the use of special adapters for the hot shoe or the special wireless control with dedicated flash units this problem can be solved.
In M Synchronization M stands for medium (time), in this type of Flash Synchronization, the flash is already triggered, even before the shutter is fully open. This is the prerequisite for flashing with central locks when shutter speeds faster than 1/30 second when flash devices with flash bulbs used.
Image : Wireless Flash Synchronization unit for DSLR for studio setup
X in the name of X Synchronization refers to the noble gas Xenon, which is used in electronic flash tube. The firing of the flash happens only by opening of the shutter. This method is the Flash Synchronization speed is of 1/60 sec to 1/500 s depending on sensor size.
Normally, the X-sync is on the center contact in the accessory hot shoe. For applications in the studio an extra port can also be triggered.
The short-time synchronization or high-speed synchronization (HSS) was developed for exposure times enable shorter than the Flash Synchronization speed.
Applications and Techniques for Flash Synchronization
Flash Synchronization is needed as its not possible to keep the Flash units ON for longer time, that would solve one big problem.
By shortening the shutter speed, the aperture is opened wider. This is also true in flash photography, a more specific influence on the depth of field is possible. Short-term synchronization prevents a fast shutter speed overexposing the image.
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