What is flash recycle time and how/why does it work the way it does?
If there’s one constant when it comes to flash, whether it’s speedlights or strobes, is recycle time. It’s the time you have to wait for the flash to charge back up between shooting one photo and the next. It applies to just about every type of flash, except for the recent array of hybrid flashes like the Godox FV200.
But what causes recycle times? Why do we have to wait? Can’t it just suck juice from the battery or the socket on the wall as it needs it? Well, nope. It can’t. And this video from photographer Mike Smith explains why.
The main reason flashes have a recycle time is because of the amount of power they expend when they give off that big burst of light. Essentially, it’s putting energy out as light in greater quantity and in a shorter space of time than it can replenish it from batteries or the AC socket on the wall. So, as Mike explains in the video, they store up energy in capacitors that can dump it all (or some of it) almost instantaneously as required. Recycle time is the amount of time it takes to charge up that capacitor to the required amount in order for the flash to be ready to fire again.
This is why, sometimes, you’ll get black frames if you shoot too quickly for the flash to fully recycle. If the flash is still charging, it won’t put out any light when it’s given the signal to fire. It’s still busy charging and rather than dump whatever amount of random energy it has gained, it’ll just not fire and keep stocking up to the required amount.
Capacitors is also why most speedlights and other battery-powered lights will see longer recycle times the more it’s used and the lower the battery’s charge is. Most batteries have a reduced voltage output as they go from full to empty. The lower the voltage at a given level of current, the slower the transfer of watts from the battery to the capacitor. It’s also why you’ll see much faster recycle times when adding an 8xAA battery pack (or a Godox PB960 or similar pack) which are capable of supplying higher voltages or more current.
Different flash powers require different amounts of energy, which is why lower power flashes have a shorter recycle time than longer ones. There are some slight technical differences between the way many studio strobes work (particularly older ones) vs speedlights and some newer strobes and how they store/limit the energy they acquire and send out to the light, but it still all boils down to charging up a capacitor.
The implications of recycle time and how to overcome them can take a little experimenting to fully wrap your head around. But once you fully get how it works and how you can change it, it makes tackling issues during a shoot go much easier and more smoothly.
Whether it needs to charge it up a lot or a little bit and how long that takes will vary depending on the flash itself, its power source, and the settings you choose.
