Yes, I think that flash exposure lock would be very useful, cutting down on the amount of settings juggling that is needed. I understand it is going to apply to P-TTL automatic exposures as well, dealing with a common complaint from Manual mode 'strobist' advocates ....namely that P-TTL exposures can change too easily between shots and are not consistent. So this new Cactus feature would really add to what we have available, allowing us to use P-TTL to get the brightness we want, but then lock it in ....effectively getting the best of both automatic and manual working!

Let's hope that Beta testing is going well and the Pentax version firmware comes out soon.

Yes, its an 'extension' via firmware update. If you have V6II transceivers and RF60x flashes then its a great free bonus! As I understand it the RF60x will become a TTL slave when controlled from a V6II, once the new firmware is installed. Note that the RF60x will not function as an on-camera TTL flash however, when directly on the hotshoe (it is still a single pin flash ... its TTL capabilities are only available via radio control).

I know Seb is keen to get going with it all (and now he has to wait for Sigma camera owners first!!), but I'd say lets not get too excited. We have to be realistic about the real-world practical applications for multi-flash automatic flash exposures. The amount of fine control, consistency and exposure accuracy are still to be proven, and many situations are going to continue to be more suited to Manual flash power control, rather than automatic.

I'm guessing that the 'XTTL' technology has come about as a follow on to the V6II's No 1 trick .... HSS. This requires more contact pins than the simple Manual trigger type, and seems to use aspects of the P-TTL communication protocol. With the communication aspects physically in place then it was a logical next step to bring on full P-TTL implementation. They obviously are marketing the 'TTL Without Boundaries' concept as something special, but I guess you're right that for many it may not be the main selling point.

Its a great bonus for us Pentax people of course, and that's why you're so keen to get going with it, as there is really nothing that would directly compare with it for Pentax cameras.

I think it probably comes down to economics .... and that's where we come in at the end of things, not the start. They will be wanting to recoup their development costs as quickly as possible, and the number of Nikon, Canon and Sony users who will appreciate a 'Cross-Brand' TTL radio solution will outnumber us considerably.

If its any comfort, there's a well known Pentax photographer, who uses the Forum Name 'Kenspo' at PentaxForums , and he has been tasked as a Beta tester for the new Cactus firmware ..... he got a box load of V6IIs and RF60x units around 3 weeks ago, and he told me he that he was going to get going with testing straight away. So maybe the wait won't be too long .....

See the PF thread here .... link ...

Kenspo posts at the bottom of the first page with a picture of his box of goodies from Cactus ..... there's even a handwritten note from Antonio telling him to 'Rock It' with the testing!

I think the 'TTL Without Boundaries ' concept is actually unique even for all the other camera brands as well ..... I'm not sure there are any other products that allow, for example, a Nikon flash to perform as an E-TTL slave with a Canon camera....?

So I think it's a new thing for everyone. I guess we have to take up our normal position in the pecking order.

Here's another one from the outdoor session .... this has more contrast created by the 'lighting ratios' . In my first one above I did actually dodge a bit on the 'fill' side of the face, as I liked a lighter look .... this one below is exactly as the flashes created with no adjustment.

Thanks Don, Peter and John . You're right Don, those sure are big catchlights! I could certainly look at reducing their brightness, although I find that Photoshop eye surgery can be hazardous

John, I think I know what you mean, when the contrast between the flash-lit subject and behind is very stark. Modelling with 2 lights should hopefully reduce the 2 dimensional 'cut-out' look, at least I hope it has here. Frankly in my situations I'm glad to get any light onto my subjects at all, let alone worry about the directions too much! I posted the same shots on PentaxForums, so I'm assuming you're talking about some other images you've seen there?

Thanks for showing us the colour ones ...... I actually think you were right to choose the Mono .... there's more of a pull towards the face with the mono. In the colour version the powerful red and blond tones compete. But its a striking effect .....

I wonder if you should reduce the red channel strength on her skin tones? .... I think a purer white tone would contrast better with the red surrounds. The warmer tones work well on the beach shot though.

They make great use of the bold colours and strong directional sunlight, and there is lots of character and energy in the postures and expression .....I can only assume your jokes are quite good!

I know that shadow effect is quite a fashionable thing, and I think you could make it even more effective by increasing the shadow depth, making it bolder (raising the black point a little). You might have to protect the shadow levels on the faces though as you do it. In any case, I see it as a positive thing and it adds depth to the shots.

My own instinct would be to move the colour balance a little away from yellow ..... Whilst it's a nice sunny tone, I don't the strength of yellow is good for the models skin tone, I think a slightly cooler balance overall would be better.

But there's some great images there. .....a very successful shoot!

Here's three recent shots of mine that I realised use very specific alternative lighting approaches, the sort of things we often discuss on here, so I wanted to show these alongside each other with an description of the flash use .... I hope the images are interesting and good for some flashy talk

First is a quite standard sort of indoor portrait, with a two-light set-up; one Main Light with a 60x60cm softbox placed to the subject's left (camera right) and a little high ..... and a 'Fill' light with Umbrella, fairly straight on to the subject. Here's an image of the set-up ....




The flashes used are the Pentax AF-540FGZ and Cactus RF60. The Cactus was triggered by the V6 Trigger on the camera, and the Pentax flash was triggered optically in SL2 mode by the Cactus output .... so Manual Mode, a mix of radio and optical triggering. The portrait is from the same session as one I showed a while back, but this one has less skin softening.


1) Pentax K7, D FA28-105mm, ISO200, F11, 1/180th






Next the baby went outside and I managed to get her propped up in her high chair This was a bright sunny day, with strong back/side sunlight, which I ended up using as a bit of rim light. I knocked out most of the ambient light, and the extremely distracting speckled highlights in behind, by moving into HSS mode, and a shutter speed of 1/500th. The same AF-540FGZ in the softbox was used as a Main Light, again off to the subjects left and facing downwards. The fill light this time was the AF-540FGZII on the camera, directly facing the subject. This was the triggering flash also, set to 'Wireless Master HS' mode. I had a P-TTL ratio split between the two flashes, 2/3 - 1/3, and a +1 compensation on the Main flash, 0 compensation on the fill one.


2) Pentax K7, D FA28-105mm, ISO100, F6.7, 1/500th






Finally the last shot is something completely different, a dynamic situation out with the family, no time to set up lighting gear, so just working with a single on-camera AF-540FGZII, with a 1/4 CTO gel on, and working to reduce the ambient a bit and bring out the subject with the flash. Here she was sitting in the shade with strong open sunshine behind, so the camera exposure settings and flash had to work together to create a photo with a decent contrast and lighting balance. I often tell people wanting to learn about flash that these sort of portraits simply don't exist without flash ...


3) Pentax K7, D FA28-105mm, ISO100, F6.7, 1/90th





Thanks for your views, I hope the shots and explanations are interesting .... Nigel

Mike, not everything is known about P-TTL exposure metering as there's no publically available technical documents .... but for a practical operational viewpoint there's some information in the Pentax Flash Manuals ..... eg, in the AF-540FGZII Manual :

1) (Page 24) ..."P-TTL Auto Flash (P-TTL)
A pre-flash is discharged before the main flash so that the multi-segment metering sensor can measure the subject’s distance, brightness, brightness difference, backlit condition, etc. The data obtained is incorporated to set the output of the main flash. This mode obtains more accurate results than with the conventional TTL mode".

2) (Page 25) .... "The correct flash output is obtained in P-TTL mode only when the flash unit is used with autofocus lenses"

This was looked at in detail at PentaxForums when I was working on the 2nd Edition of my 'Pentax Flash Guide', and the consensus is that the active autofocus points plus the focal length information is used to determine the subject distance component .... this is added to the known aperture and ISO values to produce the "more accurate results" claimed by Pentax, over the earlier TTL mode.

Check out the following 'Development Thread' at PentaxForums ... link

Whether there are any exact mount contacts used specifically for flash related information exchange is not known .... the difficulty is that the KAF2 mount and introduction of the FA and FAJ series lenses did not coincide with the introduction of P-TTL flash mode. In any case, the focus point and focal length info is 'known' by the camera already with AF lenses, so the data may just be used internally by the metering system and applied to the flash output calculation.

The main difference with P-TTL and the older TTL and Auto-Thyristor modes is that the main output is pre-determined and simply delivered during the main exposure. On the older modes the output is actually measured during the actual exposure, and quenched when the flash sensor sees enough light (either the flash sensor for Thyristor mode, or the internal camera one 'off the film plane' for TTL).

The extra distance information is needed for the P-TTL metering to determine the required output, and the reflected light returning through the lens from the pre-flash is used to make minor adjustments dependent on the subjects surface reflectivity. As the Pentax Flash Manual states, without this extra distance information, which requires an autofocus lens, then correct flash output cannot be obtained.

What the "official Line" is and what people might like to experiment with are two different things of course. People have been using A series lenses with P-TTL for a long time. Some are happy with the reliability and some are not. For the purpose of guidance I adopted and clarified the "official line" on the compatibility of P-TTL and the different lens types ...... in fact originally I didn't even include F series lenses as compatible, due to my own poor experiences with my F35-70 and P-TTL, and the fact that they were made for the original KAF mount. The jury is still out on that really .....

As a result of the discussions at the time, the PF staff carried out some detailed testing with different lens types, and the results were published in this article ..... link

The author assumed full compatibility with A types and P-TTL, but in my interpretation of the results the reliability and inconsistency rules it out. The F series was proven to be closer in performance to the FA types.