firmware updated Cactus V6II does not control power of Pentax AF540FGZII

I have the following setup: Pentax K-3II (no built in flash); a Cactus V6II mounted on top; off camera a Pentax AF540FGZII on top of another Cactus V6II.  Both V6II's updated to V1.1.004.  I cannot get the Cactus RX to control the power output of the flash.  This is NOT about HSS; just normal power controlled flash triggering
I’ll trace the steps I use to try to get the Cactus V6II’s to control the flash.  Perhaps you’ll spot an error.
    My AF540FGZ II flash has all functions set to defaults (including Fn5:Slave mode #1 “When taking pictures in wireless mode” Note: I have tried option 2 as well without a difference.).  
    With both units turned off, I connect my flash to my Cactus while listening to the hot shoe for a “click” before locking the units together.  I connect my Pentax K-3II and a Cactus V6II the same way.
    I turn on the flash; it displays P-TTL.  
    I turn on the Cactus with RX.  The Cactus displays full battery, Ch 5, AF540F2, 1/8th, the Pentax flash icon, and the radio antennae icon showing strong connection. Group B button is on.
    I turn on my Pentax K-3II, Manual mode, 1/90th, f22, ISO100, 70mm lens.  With shutter half depressed, I turn on the Cactus in TX mode.  The Cactus displays full battery, ch 5, 1/8th under the B group and the B group light is on.
    Press menu on the Cactus, Function shows HSS OFF, other items off including TLL PASSTHROUGH.  Camera & Flash System = Pentax; flash Profile Pentax AF540F2.  Power Mode: I change from RELATIVE to ABSOLUTE (SETUP)>OK and the Cactus displays “1 flash found.”
    Press the test button on the Cactus connected to the  flash: Flash fires.  Press test button on camera Cactus: Flash fires.  I adjust power settings on the Cactus TX.  Settings transfer to flash Cactus.
     With EV9.5 (lowest setting) I take picture of wall hanging.  Get a slightly under exposed image.
    I change the EV to 16.5 (highest) which the flash Cactus shows.  I take a picture.  The exposures are identical.  It would appear that the on-flash Cactus does not communicate power setting to the flash unit.
    As you might guess, I have played around with all sorts of settings without success.  The above outline is how I think the units should work.  But they don’t.
    As an aside I also have a Cactus V6–upgraded to make it compatible with the V6II.  Altho I have not tested this pair as extensively, I think the same problem exits.  Could the Cactus V6II upgrade be faulty?
   Any ideas?


  • I separately sent a note to Cactus about this problem and they had a surprising solution.  Even though in this example I am NOT using HSS, I needed to set my flash to HSS.  Apparently the Pentax HSS protocol is what Cactus uses to communicate with the flash even if HSS is not used.
  • Thanks @seriaphoto for posting your observation! :)
    Antonio Lao
    Brand Manager

    To help us better help you, always state the exact firmware version installed on your Cactus device(s), such as: "1.1.013", "FUJ.1.002", "v.103".

    For the time being, Cactus V6 (MK1) running on firmware version 2.1.001 can be triggered by a V6 II (MK2) running on Multi-brand HSS firmware (e.g. 1.1.013) and not by X-TTL firmware versions: PEN.A.001 and OLY.A.001.  No schedule has been released yet. 

    Cactus RF60X / RF60 Firmware versions A01 and A02 currently ONLY works with PEN.A.001 and OLY.A.001.  Other "A" version of X-TTL firmware will be released soon. For both Multi-brand HSS and X-TTL firmware versions (FUJ, SIG, SON), install firmware version 103 / 205 on your RF60X / RF60.

    Cactus RF60 is now an off-camera TTL flash with firmware version 205 or later!

    Metz M400 (for Fujifilm) is now supported on the Cactus V6 II (HSS and TTL).

    Nikon D750 users please read this thread: 

    Fujifilm EF-X500 users please read this thread:

    Feel free to suggest an improvement or share product ideas. Contact us directly at  At Cactus, we listen. 
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