Originally posted by leonine ... I need a good on camera flash compatible with both the 645z and the K1 in TTL mode, which will act as the master flash and fire the Canon flash remotely as the slave. ...Please recommend available options including Godox flash units.
If you need an on-camera PTTL capable flash, Godox only has two options: the
TT350-P mini speedlight and the round-headed
V1-P. The more-typical full-sized speedlight models, the TT685 and its li-on twin, the V860II
do not exist for Pentax. They may never exist. In the amount of time since the XPro-P transmitter unit has come out, both MFT and Fuji had already had all the flash models (TT685, V860II, TT350, and V350) released. It looks as if Godox is only moving forward with newer models for Pentax compatible gear, and I suspect they plan to update the older speedlights at some point.
But both the TT350-P and the V1-P can be used as a radio transmitter as well as an on-camera TTL speedlight and off-camera radio slave. They also have S1/S2 "dumb" optical slave modes built in. And the TT685-C (Canon version) and all the "flavors" of V860II can be firmware updated to do Pentax TTL, HSS, and remote power control as radio slaves. But none of them can do the "smart" optical Pentax triggering, afaik.
So if you wanted to go Godox, I would recommend ditching the Cactus V6II and 580EXII, and just get a TT350-P or V1-P (depending on your preferences to size/weight, features, and budget), and add either a
TT685-C or a
V860II (or hell, even an
AD200 or
AD200 Pro) to use as your off-camera slave speedlight. If you get
the round head for the AD200, you can share
magnetic modifiers between it and the V1.
Between the TT350 and the V1, the V1 is the higher-end more expensive feature-laden flash. The TT350 runs on 2xAA and is roughly a stop less powerful than the full-sized speedlights. It only swivels 270º, has no recycle beep, no sync port, and no external battery pack port, and its radio master UI is kinda annoying. It's also not designed to do cross-brand TTL as a radio slave. But it's tiny and really light, and if you only need a fill flash/transmitter, it's often more than sufficient. Mirrorless shooters
love it. The V1 is bigger and the round head makes it more awkward to pack, but the UI as radio master is much nicer, and it can take magnetic modifiers without a MagMod rubber band.
Flash Havoc has an
overview of the Godox system as a whole you might find useful. I think there are Amazon purchase links there. You may also want to see
this article, about the XPro-P. It was written before the firmware updates for P-TTL compatibility had come out for the bigger AD studio strobes and the V860II and TT685C, but at this point they're all compatible, except for the AD360II.