External Flashes

Slave flash

Written by Digicamhelp Editor

Slave flashes provide extra lighting in conjunction with another flash. No hot shoe or cords are needed.

A slave flash is an external flash unit that provides extra lighting when it is triggered by a built-in camera flash, or any other flash for that matter.

Slave flash setupA slave unit is particularly useful for those who want a more powerful flash but don’t have a hot shoe on their digital camera. An external flash that has a wireless transmitter lets it also function as a slave flash.

A slave flash has a built-in sensor that senses when the camera flash goes off. When the flash goes off, it triggers the slave flash, often within milliseconds.

A slave flash often comes with a bracket that has a hot shoe at one end. The bracket is screwed into the tripod mount on the bottom of a camera, then the flash is mounted on the bracket hot shoe. The flash requires no cable.

Slave flash features may include:

  • selectable power levels
  • zoom capability
  • vertical bounce angle
  • 360 degree swivel

Slave flash and digital camera compatibility

A slave unit must be compatible with a digital camera.

Slave flashes typically fire on a first flash. Since many digital cameras emit a series of pre-flashes before the main flash goes off, the pre-flashes can trigger a slave unit prematurely for it to be useful.

Manufactures make slave units specifically designed for digital cameras, which fire on the second flash. Some also have a learning mode that profiles a camera. The learning mode teaches the slave unit the number of pre-flashes for a given digital camera.

Limitation of a slave flash

A limitation of a slave flash is that it can be triggered by the flash by another camera that’s in use in the same room.


  • I didn’t try the slave flash yet, but I got an advice it seems to me correct.
    If you have a digital camera able to go manual, and a flash able to go manual, then you are set in old fashion style, no problem with synchro since in manual mode digital camera will flash only once.

  • Hi!

    you seem to already have a part of the answer figured out… Dialing down the power of your built-in flash is a good start. Make sure your built-in flash is set to first curtain so it does not trigger the slave after the scene has been exposed.

    I’m not familiar with the flashes you own, but I assume they have an auto mode. In that case, they should be able to measure the reflected light and shut themselves down when enough light has been delivered to the scene. I know that my Pentax flash performs very well in auto mode, so other quality flashes should do the same.

    Remember to set the camera to the recommended exposure parameters for each flash setting (for instance, many auto flashes assume the camera is set at f8, 1/60 seconds, ISO 100). This part is the most important to get good exposures.

    However, I strongly advise you experiment with your flash and camera before diving into the wedding. Try to find out what the room will be like and find an equivalent room (if possible) to test your setup. You might have to fine-tune the exposure on your camera to get the results you want. Test boucing, direct illumination, etc.

    Holding the flash in one hand and shooting with the other can be very, very hard, you might wat to find a way to do this differently (with a flash bracket for instance).

    Last but not least, if you want to enjoy the day at all, remind the bride and groom that you are not a pro, and that even though you will do your best, it might not always look like what they see in magazines. This will remove some stress from your shoulders 😉

    Good luck!

  • I’d love to see some advice on how to get good results with a slave flash.

    I’ve been drafted to shoot pictures at a niece’s wedding. Maybe her parents told her how they liked the results I got at their wedding many years ago.

    Back then I used a film camera, fast film, a big zoom and flash and held back for nice candids of the unaware.

    I know the puny flash on my Panasonic DMC-FZ18 will be useless if I try that technique.  It has no hot shoe to connect a big flash. (Otherwise I’m quite pleased with that camera for near SLR versatility without so much freight.)

    I already have one smallish SunPak slave flash with ability to handle the digital pre-flash, and a digital-suitable slave module I can put on my old, quite powerful Nikon SB-24 flash.  The SB-24 has variable power, ASA settings and auto exposure but I may need to go full manual to max out the range.

    My questions center on how I can trigger the slave more reliably, (the add-on module fires more reliably than the SunPak that has the built in slave trigger), and because the slave won’t be communicating with the camera, how can I make sure I get proper exposure?

    I can adjust the power on the Panasonic’s flip up flash so I would have the option of dialing it back so it’s enough to trip the slave but not add much other light that might upset the separate flash’s own auto exposure functions.

    In this case, to maximize range, I will probably want to hold the flash near the camera and fire straight forward rather than try a lot of bounce. Unfortunately I don’t know what the room will be like.