Pentax K-1, Pentax AF540FGZ II, Cactus V6 II - Reduced flash output in M mode

Hi, everyone,
I've just joined this community, I am a Cactus user since last August.

I'm asking for your help to solve a problem with the following equipment:

Pentax K-1
Pentax AF540FGZ II
2 x Cactus V6 II

The flash output reaches the full power in TTL mode, but in M mode at power 1/1 the output doesn't reach its GN54, it's about 1EV less.
To use M mode I leave P-TTL on the flash body.

If I set M mode both on the flash body and on the V6 II the output reaches the GN54, but it shoots only at full power, the setting 1/2 ÷ 1/256 doesn't affect the output.

I've made my tests to be sure, even exchanging the triggers TX-RX, I've updated the firmare to the latest version V3.07.

Can you kindly find a solution?


  • Finally I've found how to restore the normal functioning thanks to this forum, it was enough to do a Factory Reset. Surprisingly the triggers have kept the firmware PEN.A.005.
    Thank you anyways.
  • edited February 2019
    The problem takes place again, and this time Factory Reset doesn't help.

    I have tested my system.
    I set P-TTL mode on flash body and M mode on V6 II.
    At zoom 24 mm the flash works properly, at zoom 28 the output is reduced by -1/3 EV, it decreases gradually until -1 EV at zoom 80 mm.
    In TTL mode all works properly.
  • Another limit that I found is that V6 II doesn't trigger in live view mode.
  • @raychan

    Hi Raychan,

    poor Chernobog does not appear to make it through to Cactus support.

    The described behaviour could be due to some weird P-TTL flash logic, but it could also be due to a bug.


    Have you tried the multi-brand version (e.g., V1.1.019)?
    If you don't need P-TTL, the multi-brand version may work better for you. Might be worth a trz, even just for troubleshooting to see whether you'll observe the same loss of power when using manual power control.
  • @Class A This could be a bug. Let me check with our engineer for further assistance.
    Ray Chan

    Senior Product Specialist
    Harvest One Limited
  • edited February 2019
    @Class A

    I haven't tried a multi-brand version, I rely upon manual mode, but I may need P-TTL mode with mixed lighting. For the everyday use I can by-pass this bug because I don't set the zoom to 85 mm, I usually set zoom to 24 mm, in order to cover the angle of a softbox or an umbrella.
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