Cactus Radio P-TTL Update Released

Cactus Imaging have released a firmware update for their V6II Transceiver, RF60 and RF60X flashes .... This is known as 'X-TTL', and it brings P-TTL automatic flash exposure metering, P-TTL HSS, 2nd Curtain Sync and Off-Camera AF Assist to the trigger system.

To obtain 'X-TTL' functions for Pentax, you need 1. & 2. below , plus either 3. or 4. or both 3. & 4. mixed

1. A Pentax DSLR with P-TTL
2. A Cactus V6II Transceiver in Tx mode (updated to the new firmware - "PEN.A001")
3. One or more Cactus RF60 or RF60X Flashes (updated to the new firmware - "A01")
4. One or More Pentax Dedicated System Flashes (P-TTL) - (eg Pentax, Metz, Sigma, Shanny, Yongnuo) ... PLUS .... each flash in this category requires a V6II attached in Rx mode (updated to the new firmware - "PEN.A001")


With this system you will have the ability to instantly switch between P-TTL automatic flash metering and Manual Mode flash control, and you can choose either mode for any Group in your set-up. You have 4 groups with independent control from the V6II Tx on the camera.

In P-TTL mode the V6II will offer a Flash Compensation setting (eg -2.0, +1.0 stops) ..... In Manual mode the V6II control will offer Manual flash power steps (eg 1/2, 1/16th), in the same way as the present Cactus system operates.

So it may give us the best of both worlds ..... :

I have not got this up and running on my own equipment yet, so I can't give detailed pointers on the operations, but I have read the Notes for the other camera system releases so far, and it is fairly simple, with most things being automatic once set up. The main buttons for selecting things will be the 4 Group buttons and the Main Menu button on the V6II. The flashes will operate in the 'Auto-HSS' (RF60) mode, or P-TTL mode (dedicated system flashes). HSS switching should be automatic as at present, with the flashes jumping in and of HSS mode as the Time Value changes around the max sync speed.

For more info, here is a link to the X-TTL Website .... link
Here is a link to the Firmware Download (this is done through their own dedicated Firmware Software, which you should install on a computer .... the actual firmware is selected from within the Software) .... link

You may find more related talk on the PentaxForums Flash section here ..... link

I updated mine today Nigel and had a little play. Impressed so far using the K1 in Manual mode and let the Camera and Cactus take care of the rest.

The flash compensation runs from -5 to +5 in 1/3 stop increments. Adjustable by group.

The ability to mix TTL with manual control in the same setup is awesome.

All this is controlled from the TX unit on top of your camera. Whats not to like ?

Good to hear Peter, sounds like the updates went smoothly. The V6II has got to be one of the most intuitive and practical Radio Transmitters / Flash Controllers available ....

Another interesting feature is the 'exposure lock', which is a way to hold and fix a flash exposure value following P-TTL metering, therefore removing any inconsistencies caused by continual re-metering for each successive shot. That should be an interesting and useful thing .... I'm just not sure how they decided to implement it exactly yet. It doesn't sound as if there are any Pentax-Specific instructions, so we may have to test this out ourselves to get a good feel for it.

The only negative development that has emerged during the work on the Pentax firmware is that they can't provide 'Cross-Brand' TTL for Pentax .... so as per my list above, we are limited to Cactus flashes and P-TTL Dedicated System flashes (not another brands TTL models, eg Nikon SB900 etc). This will prove a limitation for some people who may use multiple systems and have a range of different flash brands, but I guess the majority of Pentax shooters buying into the V6II system will mainly have Pentax and Metz etc flashes. If they don't then its hard not to recommend the RF60X as a great option if you're starting out, and are only looking for Off-Camera P-TTL.

For on-Camera work then the Pentax models remain ideal ..... add another V6II and you can also use a Pentax flash for Off-Camera Radio P-TTL as well.

For the exposure lock the new QS guide says you first enable it in the menu , then activate it (after taking a picture) by pressing the wheel. Either global or by group.

Have yet to try it out.

That sounds handy. I've always liked the V6 / V6II design with the dial that also presses in, very quick and handy once you know whats what! The assumption about the Exposure Lock is that it is a temporary 'power hold' function .... ie it fixes the power output that was needed to obtain the metered flash EV temporarily.

I've argued elsewhere that it is not really a true 'exposure lock', not in the literal sense of those terms, because that would imply that the flash exposure value would remain fixed, and in TTL operations that means actually a varying flash power response to other changes (eg distance, Aperture ISO). So looked at in this light it is more literally a 'flash power lock'.

However I know that Cactus were looking at finding a way to apply automatic flash power adjustments in Manual Mode .... this would be in order to hold a fixed Flash EV while other things changed, eg the aperture or ISO, or Time Value also in HSS mode . This would be very convenient, especially for Manual Mode HSS work, as it would remove the need to adjust the flash power every time you changed something else. I'm not sure if this was achieved in this first Firmware implementation, so that would be good to find out.

.....Ahhh, I've seen the Quick Guide now ... there are the two things I mentioned : They call them 'Flash Power Lock' and 'Flash Compensate' ...(I did try and warn them against using the unfortunate term 'Compensate' as I think its confusing in a flash context, but it was too late, they were already committed to the term with the already released firmware's and printed material). ....anyway, 'Flash Compensate' means holding a fixed Flash EV ....see what I mean?

My time for actual photography is severely curtailed lately, and I'm struggling even to find the time to get these Cactus items updated!

Here is the Link to the Pentax specific V6II X-TTL Quick Start Guide .... link

I have been in the beta program for a while, but didn't have the chance to play with it much. Anyway worked well for the tests I did. TBH I am still scared to use it outdoor with models, as they resulted unreliable so far (now three times they failed on me)

If it is any help try this. When you have everything set up have the TX unit in M power control mode and cycle the power setting up and down for all groups. I find I dont get the false starts this way. Try it irrespective of whether you are using the cactus to simply fire the flashes in M flash mode, or using the P-TTL protocol to manually control flash output from the TX unit, or now using the flashes in P-TTL mode.

Can I confirm something then please, - Nigel - you seem to be well up on these !!

My understanding is with these triggers we ( Pentax Users ) can now get flash sync at speeds over and above 1/200 sec albight at lower power or the flash closer to the subject ?

And all this wireless with a Pentax or Metz flashgun ? I know they'll need a trigger attached to all the flashguns plus the camera.

If that's correct, that's of far more use to me then P-TTL

thanks for the message, what do you exactly mean with false starts?

it supports HSS yes.

Thanks Sebas77,

Have you tried it ?

The blurb says speeds up to 1/8000 sec, I'd prob only go to 1/2000 sec, have you had reasonable results so far ?

I have tried in the sense that I have tested it yes. It works nice. This was a test:




however after several months I bought them, I am still not able to use them during a real photoshoot. At the moment I am waiting to have a studio to properly get used of them.

Pretty good, thanks for your help, just ordered 2 from Wex, I do a fair amount of portrait shoots so will arrange a test asap

Yes Chris, Radio Manual HSS has been the V6IIs main trick , up to 1/8000th..... here's a couple I prepared earlier ...













These were between 1/500th - 1/1000th sec, f.6.7, ISO 100 ..... in bright open sun. The RF60x flash is in a softbox, just out of the frame, around 1/4th power (so still plenty more oommph if needed).

The new thing with this firmware update is the P-TTL metering .... this is certainly a 'nice to have', not essential of course. But I'd say that for HSS work outdoors it will be very handy, because it will remove the need for compensating flash power adjustments every time you change aperture or ISO, or change the distance, or the natural light changes (sun behind clouds etc).