Configuring my Speedlite 600EX-RT flash & ST-E3-RT

Configuring your gear to work to fit your individual style of working is essential, the Speedlite 600EX-RT includes custom functions C.Fn and personal function P.Fn. With so many photographers and ways of doing things camera makers provide a range of settings to customize how each piece of kit works for you.

Configuring Speedlite 600EX-RT

I’ve been working with the Speedlite 600EX-RT and ST-E3-RT transmitter since April 2012 and with use I have now developed my approach to configuring the C.Fn and P.Fn settings.

Custom Functions (C.Fn)

Speedlite 600EX-RT custom functions set from EOS 5D Mark III

Speedlite 600EX-RT custom functions set from EOS 5D Mark III

I have the following configuration, changing five custom functions in each Speedlite 600EX-RT.

  • C.Fn 00 left at 0: default
  • C.Fn 01 left at 0: default
  • C.Fn 02 left at 0: default
  • C.Fn 03 left at 0: default
  • C.Fn 04 left at 0: default
  • C.Fn 05 left at 0: default
  • C.Fn 06 left at 0: default
  • C.Fn 07 left at 0: default
  • C.Fn 08 set to 1: disabling the AF illuminator. With off-camera use the flash is often in a soft box or umbrella obscuring the AF illumination anyway
  • C.Fn 09 left at 0: default
  • C.Fn 10 left at 0: default
  • C.Fn 11 left at 0: default
  • C.Fn 12 set to 1: uses the external CP-E4 battery pack to charge the flash not the CP-E4 + flash batteries
  • C.Fn 13 left at 0: default
  • C.Fn 20 left at 0: default
  • C.Fn 21 set to 1: guide number priority when using the automatic flash zoom (not very often)
  • C.Fn 22 set to 2: set to 1 to keep the rear LCD illuminated
  • C.Fn 23 set to 1:  to only show the red LED on the back of the flash when it’s charged, not flash the AF illuminator

Note:

C.Fn 00 – C.Fn 13 can be set by most recent EOS cameras from 2007 onwards using the camera flash control menu and External flash C.Fn setting option

C.Fn 00 – C.Fn 23 can be set by the 2012 and later model cameras like the EOS 5D Mark III

Personal Functions (P.Fn)

Personal functions can only be set on the flash itself, none of the current cameras can set the P.Fn from the camera menu system. You will need to press and hold the Zm/CFn button for about five seconds to access the C.Fn settings, then release it and press it again to access the P.Fn settings.

  • P.Fn 01 left at 0: default
  • P.Fn 02 left at 0: default
  • P.Fn 03 left at 0: default
  • P.Fn 04 left at 0: default
  • P.Fn 05 set to 1: Off which ensures that the flash won’t try and detect the colour of filters used. Since the flash only seems to work ok for orange filters I opt to disable this filter detection, it also means no warnings when using velcro speed straps to attach modifiers.
  • P.Fn 06 set to 1: Off <-> ‘radio mode’, this makes my flash go from standalone to radio flash master to radio flash slave and then back to standalone operation completely skipping the older pulsed light master / slave modes.
  • P.Fn 07 set to 1: Enables the flash to fire when being used in Linked Shot mode. This is one of the few P.Fn settings that I change often depending on the shoot needs.

Some of these settings have changed since I wrote about how I store my settings in the Speedlite last year.

Configuring Speedlite Transmitter ST-E3-RT

Setting personal functions P.Fn on the ST-E3-RT

Setting personal functions P.Fn on the ST-E3-RT

  • C.Fn 01 left at 0: default
  • C.Fn 02 left at 0: default
  • C.Fn 03 left at 0: default
  • C.Fn 04 left at 0: default
  • C.Fn 07 left at 0: default
  • C.Fn 13 set to 1: to allow direct access to the flash exposure compensation using the quick dial on the ST-E3-RT
  • C.Fn 20 set to 1: ON to ensure the ST-E3-RT beeps when all the slaves are recharged
  • C.Fn 22 set to 2: set to 1 to keep the LCD illuminated

Personal Functions (P.Fn)

Personal functions can only be set on the Speedlite transmitter itself, none of the current cameras can set the P.Fn from the camera menu system. You will need to press and hold the CFn button for about five seconds to access the C.Fn settings, then release it and press it again to access the P.Fn settings. I don’t make any changes to the default settings.

  • P.Fn 01 left at 0: default
  • P.Fn 03 left at 0: default
  • P.Fn 04 left at 0: default

Further reading

Canon USA has a really useful PDF guide with explanations for each of the custom functions and personal functions in the Speedlite 600EX-RT. Download a copy of the PDF