Both those confusions' have been raised on other forums, so you're not the only one!

TTL pass through refers to the option of having a dedicated system flash (like your Metz) on top of the V6II on the camera .... It's an impressive looking tower! The flash ignores the V6II and behaves as if it's directly on the camera.

I use this configuration to mix my systems... So the V6 controls my RF60, and a Pentax flash on top (with TTL pass through mode activated on the V6) controls my other Pentax flash (which could be operating in either P-TTL or Manual slave mode). So I get to use all my flashes together, combining radio and optical triggering simultaneously!

The Cactus firmware update coming does promise real TTL automatic metering on Pentax cameras with a cross-brand range of dedicated system flashes. The published limitations don't apply to Pentax, from what I can gather via informed sources at Cactus and PentaxForums.

Whilst the Cactus triggers are hardly budget items, you are talking about a fairly specialised (and rarified!) technique (off-camera radio HSS) .... Even though on Nikon and Canon there are more easy options to achieve it, in many cases that involves expensive TTL equipment.

If I can get images as good with my 28-105 on a future K1 as I get with it now on the K7 I would be perfectly happy! Anything more would count as a bonus.

The Metz becomes a 'Manual HSS' flash when it's used with the Cactus V6II triggers At present that's all that the triggers will provide, although with the advantages of remote radio control. However the promised firmware update in future will unlock TTL metering as well, and so we should then get the option of automatic HSS metering as well.

My own preference is to work with automatic HSS, because it's less workload. However, that means sticking to P-TTL wireless triggering (which has limitations outside in bright light) or trying the Acon R930 triggers, which reportedly have a fairly unproven track record in terms of multi-flash slave control.

If you're talking about using the Metz flash with a Cactus system then you always need a 2nd transceiver .... the Metz flash needs a V6II on its hotshoe in Rx mode to receive the radio trigger signal.

The only way you can avoid buying 2 or more V6IIs is if you get the Cactus RF60 flash, which includes a built-in V6II unit.

The Cactus system enables remote power and flash head zoom control from the on-camera Tx unit (4 groups are possible).

What you say about the 'Manual HSS' flash type (eg Cactus RF60) is basically right .... that's all it does, fire a continuous pulsing burst for 1/180th sec at the set power . The power can be set remotely from the V6II Tx .

The Pentax flashes are exactly the same, so its probably to do with limitations in the system itself. Off camera its the same for non-HSS as well .... (we can't control a wireless slave flash in manual mode from the camera, we have to walk over to it and change the power directly). I'm not sure why 'Manual HSS' can't be done with P-TTL flashes on-camera ..... but really, I prefer automatic HSS, because the extra juggling of power settings for each shutter speed adjustment is an extra burden.

With a P-TTL flash on the camera hotshoe and an M series lens, you should be able to engage HS sync mode on the flash (use M exposure mode and set the time value shorted than 1/180th sec). However, you cannot expect any flash exposure consistency, because the metering system has no aperture or subject distance information. Flash exposures are likely to be hit and miss. In fact the flash may well fire at full power with no exposure control at all.

However, with a Cactus V6II system, which uses 'Manual Mode HSS', then you will have full manual control over your flash power, in the same way as with an autofocus lens. This is because the lens type is not critical to the exposure calculations, which is all fully manual. The Cactus system does not transmit aperture, ISO or distance information in any way.

The Guide was created for the 'Pentax Community', those people who are members of a few forums and who I communicate with via those outlets. To be honest, the target market is very limited in the context of things, and I'm not a professional writer. If the brand continues to grow and the flash system develops as well then with a larger global interest there might be some commercial potential. I will keep developing the resource, and see where it may lead in the future. I don't have any personal outlets to develop .... I'm not online at all apart from a few Pentax forums. I can't even find the time to maintain my 500px account!.

In the flash manuals there is a reference to additional shutter speed information being transmitted in the pre-flashes to wireless slaves for HSS mode .... I interpret this as meaning that that exposure time value must be factored in for correct flash exposure for HSS mode, and this is added locally by the flash. (in non HSS mode then 'shutter speed' does not affect flash exposure).

The P-TTL metering system uses a distance component in its calculations, in addition to aperture and ISO .... the distance to the subject is made up from focal length and focus point information. The transmission of this information depends on the contacts through the mount, and having an autofocus lens. The A series dates from before this data was transmitted, indeed in my view so was the F series. However there is very little technical knowledge of what exactly the KAF2 and FA lens series added that was flash specific. So the consensus view is that the F series must be included ..... therefore the 'official' guidance is in line with what the Pentax Flash manuals now state ...that P-TTL is only compatible with autofocus lenses.

You're right ... all that Cactus needed to do was make the camera 'think' there was an HSS enabled flash on the hotshoe. Without that, there can be no flash trigger signal generated. In the case of the Godox trigger we saw in your linked video, with the Godox trigger on the camera directly, in Manual exposure mode once the time value was set to 1/250th or shorter, no flash would fire. So the guy has to put the Godox trigger on top of the Cactrus trigger, which then passes the trigger signal through to the Godox, which then relays it to the slave flash (via that systems receiving unit).

The Guide is primarily about the Pentax proprietary flash system, so direct explanation of the Cactus triggers is beyond its scope, but the new supplement will have some general guidance on different types of radio trigger technologies, and will name some specific products in each category.

No, I was looking to make my first million ! .

It's a good question .... I have always had an interest in manuals and technical guides, and I started to naturally write up things for the forums, do demos and promote discussions when I got seriously into DSLR photography.

Flash photography is perhaps an ideal mix of the technical and creative, it's one of those areas of photography where you do need to study up and understand the technologies and physics of it all in order to achieve things consistently. You can't just fiddle with settings, take practise shots and expect it all to work out! And because I was enjoying my flash work so much it was a good outlet for that desire to lay things out on 'paper', organise and structure the knowledge.

The hobby for me is just as much about the Guide and the discussions as it is about the actual picture taking. Of course there are many days when no picture taking is possible and so the forums and discussing flash matters makes up for that!

There's been a fabulous response to the guide, on both sides of the pond, plus more stimulating and better informed discussions as a result. There's a more balanced understanding of automatic vs manual flash working as well, and the pros and cons of each, as more people are understanding how to get better results from P-TTL dedicated system flashes.

The project is ongoing, and I am not far off completing a new 'Guide Supplement' document, of around 30-40 pages, which builds on and extends the current Guide edition significantly.

Of course I do derive great satisfaction from reading about people like yourself who have found the guide to contain helpful info not easily available elsewhere and especially when I hear that it's led to better quality photos and being able to create images that they couldn't ever before.

Great, that looks good .... Nice controlled background . It's cool how the sun can often provide us with a powerful and free rim light! HSS allows this to he controlled without blowing out the highlights. Dial in 1 or 1.5 stops of plus flash compensation to bring that statue out a bit more if you want.

I'm glad you've got going with it now, and pleased the guide helped. Looking forward to hearing how things progress towards off-camera HSS ......