Once you start working with 2 manual off-camera HSS flashes and trying to balance their output with the sunlight, then I'm sure you will appreciate Manual mode!

Good luck with your HSS experiences. Just getting the right bunch of triggers and flashes together and getting them to sync properly can be quite a challenge , let alone all this flash and ambient light balancing ! But you sound committed so I am sure you will have good success. Looking forward to seeing some of your photo results sometime

Maybe we don't need to use the green button ...? It is really a way to reset parameters to their default positions. In this case of ambient light metering in M mode that will probably just be the 'program line' defaults .....but I hope someone with more knowledge of this sort of camera feature will help here.

You might be able to just point the camera, half press with the shutter and adjust from there. It may be that the settings in M mode will stay where you last left them if you don't press the green button. The green button is a good way to get straight back to a start point when things have gone astray.

At the time that response was written I thought the Av with AE lock to be a fiddly way of doing it, and I still think so. Av mode is for situations where the aperture is your 'priority' and the shutter speed can vary for correct exposure, given your exposure compensation setting. With HSS working the shutter speed affects both the ambient exposure AND the flash power needed. For precise control of all factors and for the fine tuning adjustments needed then M mode gives you it all.

I think the exact parameters that change with green button presses in M mode may depend on a custom setting ...('Tv shift' comes to mind) , but hopefully another member can advise more about this as I'm not really sure ......I find a quick point of the camera to the sky or bright parts of the background, press of green button, then tweak of aperture and shutter to get the DOF and brightness needed is a good way to control things. Having everything remain fixed until you specifically adjust anything again is a plus also I think.

And also I would avoid auto-ISO for all flash work .....choose a fixed ISO, and for HSS it's difficult to recommend anything other than ISO 100.

There's almost no known documented technical details on the P-TTL metering system, but the information used to help the pre-flash determine correct flash exposure includes aperture, ISO, focal length and active focus points. The pre-flash fine tunes this by taking into account the amount of light reflected back through the lens. Some of this information depends on contacts passed through the mount from autofocus lenses, so for that reason manual focus lenses are not compatible with P-TTL, or the subset functions of that mode (such as HSS).

The Cactus system can remotely control the power of P-TTL flashes, and you need one unit for the camera hotshoe and one for each flash. In the case of Cactus's own RF60 flash then the radio receiver is built into the flash, so no receiving V6 is needed. Remember this is a system for manual flash power only, including for HSS working. If you want radio triggering for HSS then you need the V6II units ..... the original V6 does not support HSS.

Here is a link to a demo thread I made showing traditional Optical triggering with HSS using 2 Pentax P-TTL flashes and a Cactus RF60 ....

link

Bill, some beautiful forms and lighting patterns. You have isolated some very attractive little ripples and brought out contrast, depth and colours to make very polished looking, creative images.

I must be honest and add that overall, as photographs, I find the effect of viewing to be strangely claustrophobic .... it's as if my eye is needing to pull away, look around and straining to take in a wider vista. It feels like more space is needed. I'm not sure if this is just an awareness of the sort of wider environment and a need to explore more visually, but these are an oddly constraining view of a beach with an unsettling effect when seen.

Taken as mini scenes, a micro world, then all the qualities I referred to at the start (and indeed as described by other members here) shine through.

Yeah, I imagine that the clever automatic format detection stuff is the preserve of proprietary camera brand systems with their own equipment. It's interesting that the original AF-540 FGZ model uses the 'Digital' label to describe the aps-c format setting, because when the flash was designed aps-c was the only digital format in the range !

I guess nowadays it's quite possible that a Pentax photographer might mix and match their flash unit between a K3, K1 and 645z! Then the automatic format detection would save some time and effort. For most of us it's going to be a set it forget it type of thing.

Glad to help, ask away anytime.

Automatic flash head zoom is only compatible with autofocus lenses, so you would have to manually set the zoom with an A type lens.

As Yves said, for many flashes the display will indicate the FF figure. With Pentax we have more sophistication in that the AF-360/540 FGZ can automatically detect the camera sensor format (aps-c, 35mm, 645 etc). In the case of the older 'mk1' models there is a manual override for this setting also.

This is really only directly related to the actual field of view when the flash is on the camera and pointing straight ahead. For off camera and bounced flash situations then the flash head zoom setting is fairly unrelated to the actual lens focal length, and is mostly a creative choice. Even on camera and directly ahead then we often don't need to illuminate the entire frame, as our subject may only take up a small area, so a longer setting on the flash zoom may be more efficient (it will use less power for the same exposure as the light is concentrated into a tighter beam).

If you had the camera format incorrectly set on a flash you risk wasting power though .....say you were using a 55mm lens on an apps-c camera; if the flash zoom was set to, say 50mm, and the format was FF, then a lot of the light would be wasted around the outside of the image frame. It would be necessary to manually zoom the flash head in to, say 80 or 85mm to match the actual field of view being both 'seen' by the sensor and illuminated by the flash.

Automatic format detection has the advantage that this conversion is carried out and even though the flash head will be at the position for illuminating a FF field of view of 85mm, the actual display on the flash screen will show 50 or 55, so relating neatly to the actual lens focal length.

For a fuller rundown see Section 8 in my guide, 'Flash Head Zoom and Camera Format', pages 46-49 (downloadable from the link in my signature here ...)

I think it's just that when you're actually actively managing the balance of exposure between elements of your image, which is what we're doing with a flash-lit subject and ambient natural light in behind, that it needs that even more exact and direct hands-on control of manual mode.

Of course this applies just as much to non-HSS work as well, wherever we need to balance these two components of exposure in the same scene. It's just that for HSS those modes are 'mechanically' a requirement to actually get the shutter speed under control.

Here's another link to another thread I did covering a non-HSS situation, balancing indoor ambient light with bounced P-TTL in the pub.....

link

I don't find that Av makes sense for HSS, because the exposure time ('shutter speed' ) is critical to your control over the background ambient brightness. So I find it's good to have direct control over that component with one e-dial ....generally we want to fix the ISO at 100, set a wider aperture for a nice portrait with background OOF, then juggle the shutter 'speed' to control the background exposure.

You could get Cactus V6II triggers to use with a P-TTL flash for HSS, or add in a Cactus RF60 flash or 2 .....but flash exposures will be Manual mode only. You will be able to remotely control the flash power but it's one extra thing to juggle during HSS operations.

Here's a link to an HSS demo thread on this forum showing the practical steps with photo examples ....

link

High speed sync flash is only compatible with M, Tv or Tav camera modes (i.e those where the time value can be directly input). In my view M is the most intuitive and practical working mode for HSS operations.

Be aware that HSS is generally a subset of P-TTL flash mode, and P-TTL is only compatible with autofocus lenses ....therefore good exposure control with an A type lens should not be expected. However, mechanically, everything should work ok with the aperture ring set to the A position, and you may find that HSS exposures are ok, but not as consistent as with an autofocus lens.

With older, M or K type lenses, then use either Auto (thyristor) or Manual flash modes. HSS will not be available, unless you use a flash where manual HSS is possible.