[mcgregni]

The days when Pentax could be criticised for lacking Radio TTL flash options seem to be well past us now ....

But now that there are a small number of quality flash trigger systems offering TTL to meet the demand, it begs the question of what exactly are they suited for and why would we want to pay extra for the automated flash exposure control, when so many "strobists" so vocally advocate full Manual power control as soon as we take a flash off the camera ?



Here's a few that show how I've been using "Radio P-TTL" recently ......




















Here's a crop of the 2nd one .... hey, who says you can't crop much with only 14.5mp ?!? (the K7's still going strong, but I will be trying hard for one of those giveaway K1s neverthless !)






The shots were lit with 2 Cactus RF60/x flashes on a a multi adaptor firing into a white reflective umbrella ....





The backlight is kindly provided for free by the sun, and the ambient exposure was dialed down a couple of stops to reduce clutter behind and keep the rim light under control .....

The trigger is the Cactus V6II, set to TTL mode. Both flashes work on the same group and fire together. The light ouput automatically divides evenly between the two..... having two creates a wider spread of light and also allows faster recycling due to halving the power used by each flash to achieve the exposure.

Pentax K7 ; D FA28-105 ; ISO100 ; 1/180th ; F5.6 - F8.0

Why TTL for this, not manual? Of course, you could still be a "Real Strobist" and use Manual, but here's a good use case for automated flash exposures ..... because with these kind of subjects, and with such an informal relaxed situation then I was frequently moving the umbrella around to follow the kids and get the angles right. With distance changes and the mix of ambient light with flash changing also, I benefitted greatly from the instant automated adjustments made by the TTL system to hold the exposures on the faces consistently ...... generally I was using around +0.5 to -0.5 flash compensation settings, fairly normal for portrait work like this.

Thanks for taking a look and I hope you might be encouraged to look at some Radio P-TTL for your outdoor portraits!

Nigel

[Saltwater Images]

Nicely captured images. I shoot with the original Cactus V6 in manual mode. At first it was to learn manual flash. Once I added a Sekonic L-308S Flashmate to the mix and got comfortable with metering from different angles for different effects is speeded up workflow and enhanced results.

In the past TTL has let me down on occasion while manual flash places the fault in my court when results are not great. That’s the biggest reason I shoot manual flash. The Sekonic lightmeter also seems more accurate than the in-camera meter.

Your Cactus V6II results look excellent. I may pick up a V6II and do the firmware update on my four RF60’s and try it out. Thanks for posting.

[mcgregni]

Thanks, I'm glad you saw the photos! I have found the automatic exposures obtained with this system very reliable and usually spot on to what's needed..... A quick flick up or down a half stop is usually all that's needed. The independent control over two flashes in TTL mode is very impressive to me also, and I prefer working in "stops" for exposure control.

[mcgregni]

Well thanks to all who have viewed and Liked. I admit I am puzzled that there's not some more interest here ..... There's more talk on threads about what first equipment to buy when starting out, which is all well and truly been done here over and over. This is about some real world applications and for real world people. ..... Us!

Come on all you Moms and Dads, Grandpa's/ma's, uncles and all .... What do you think about getting out with some Radio P-TTL ? It's not too hard once you get the exposure balancing under control, and you can leave so many technical headaches behind you.... Contrast issues, blown highlights, faces in shadow, movement blur, noise .....all gone! You don't even need a K1 !

[kaseki]

...

Come on all you [geezers]l .... What do you think about getting out with some Radio [old-time TTL] ? It's not too hard once you get the exposure balancing under control, and you can leave so many technical headaches behind you.... Contrast issues, blown highlights, faces in shadow, movement blur, noise .....all gone! You don't even need a [645Z] !

Heh! What I would need would be an RF system that presented whatever a 645N put on its hot shoe connection to the AF500GTZ flash hot shoe interface, and presented whatever the flash put on its hot shoe interface to the 645N hot shoe. In other words, I would need an analog duplex 4 signal plus ground communication link. I suspect it would be much less effort to just take a 3m Pentax 5P cable, cut it in the middle, and extend it with 5-conductor cable to whatever length the shooting scenario required. An RF cable choke might be desirable to suppress any induced or generated high frequency noise -- another experimental project that I don't really need to pad my to-do list for the summer.

So, mcgregni, what has been the longest distance you have ever used for P-TTL with an RF flash link?

[mcgregni]

Geezers, yes, that has nice ring to it! I remember reading the thread where you were looking for advice on the 645N and AF500 FTZ combo ..... I'm afraid that film era TTL stuff is all a bit before my time. I'm certainly old enough, but started late with photography, not getting a proper SLR system until around 1999 and only dabbling with flash back then.

I only work in fairly close proximity to my subjects when using off camera flash, so the maximum range I've ever tried is up to about 5meters. I even keep my V6II on the short range setting permanently, and have never had any issues with misfires. Good luck with getting your flash up and running with the 645N.

[Class A]

So, mcgregni, what has been the longest distance you have ever used for P-TTL with an RF flash link?

The V6II with the multi-brand firmware has no problem supporting distances up to 100m.

I haven't tested the X-TTL firmware variant (the one that supports P-TTL) for maximum reach but it should support a very similar, if not the same, range.

What I would need would be an RF system that presented whatever a 645N put on its hot shoe connection to the AF500GTZ flash hot shoe interface, and presented whatever the flash put on its hot shoe interface to the 645N hot shoe.

If it is possible to optically trigger/control the AF500GTZ then the Aokatec trigger system could be the solution you are after.

[kaseki]

Geezers, yes, that has nice ring to it! I remember reading the thread where you were looking for advice on the 645N and AF500 FTZ combo ..... I'm afraid that film era TTL stuff is all a bit before my time. I'm certainly old enough, but started late with photography, not getting a proper SLR system until around 1999 and only dabbling with flash back then.

I only work in fairly close proximity to my subjects when using off camera flash, so the maximum range I've ever tried is up to about 5meters. I even keep my V6II on the short range setting permanently, and have never had any issues with misfires. Good luck with getting your flash up and running with the 645N.

I have successfully run mulitple flashes in TTL mode using the Pentax 5P cables and various F connectors to parallel flashes. It is possible, I think, to use the F connectors to make two 3-m cables into a 6-m equivalent cable. For more distance, or for the convenience of not having to use up two or more cables for just one flash, a splice using some decent connectors (the options are vast -- but Cannon microphone cable connectors flitted through my mind at the thought because the typical microphone cables used with them are very rugged) might be more versatile when switching from indoors to outdoors.

The V6II with the multi-brand firmware has no problem supporting distances up to 100m.

I haven't tested the X-TTL firmware variant (the one that supports P-TTL) for maximum reach but it should support a very similar, if not the same, range.

If it is possible to optically trigger/control the AF500GTZ then the Aokatec trigger system could be the solution you are after.

The AF500GTZ flashes can work optically as slave flashes, but not in TTL mode. I will look into Aokatec to see what they have. Thanks.

Edit: The Aokatec seems to be P-TTL only.

[Class A]

It is possible, I think, to use the F connectors to make two 3-m cables into a 6-m equivalent cable.

Seems a lot of effort to deal with long cable connections just to get support for flash exposure control.

With a 645N you are probably not photographing action so it would seem simpler to trigger off-camera flashes via radio triggers and manually control the flash power. If you are concerned about not getting the power levels right using guide numbers and measuring distances then a flash meter should do the job.

The AF500GTZ flashes can work optically as slave flashes, but not in TTL mode.

If TTL mode is not supported "wirelessly" then there is no point to looking into the Aokatec system.

The Aokatec seems to be P-TTL only.

I'm pretty sure that the Aokatec system is flash system agnostic. It just converts optical signals into radio signals and back. So if the AF500GTZ would have supported its TTL magic via optical communication with another camera flash then I'm rather sure the Aokatec system would have played with it.

[kaseki]

Seems a lot of effort to deal with long cable connections just to get support for flash exposure control.

With a 645N you are probably not photographing action so it would seem simpler to trigger off-camera flashes via radio triggers and manually control the flash power. If you are concerned about not getting the power levels right using guide numbers and measuring distances then a flash meter should do the job.

If TTL mode is not supported "wirelessly" then there is no point to looking into the Aokatec system.

I'm pretty sure that the Aokatec system is flash system agnostic. It just converts optical signals into radio signals and back. So if the AF500GTZ would have supported its TTL magic via optical communication with another camera flash then I'm rather sure the Aokatec system would have played with it.

In principle, TTL should only require the communications mode to achieve two functions -- trigger the flash, and quench the flash -- both signals emanating from the camera. Flash can optically trigger other flashes, but this doesn't help quenching. (An optically slaved flash head could, if so designed, quench when the master flash quenched within some signal-to-noise limits, thereby extending TTL to multiple flash heads.) The AF500FTZ doesn't do this. Pentax also expects the flash to provide other data, and expects to command the flash beamwidth, so there is some digital data passed each way.

An RF system intended for old-time TTL could signal flash trigger on one channel and quench on another channel. A highly motivated EO engineer could build an optical flash detector module that triggered on the trigger hot-shoe pin when there was a flash and quenched on the quench hot-shoe pin when the flash ended (or on the counterpart pins on the AF500FTZ 5P connector). I'm not going to spend the time to do that because cables are more practical, more positive, and probably more accurate in flash timing. Further, the distances are not beyond modified cable capability.

Anyway, I do have a Minolta Flashmeter IV to use when setting powers, distances, and diffusers, so it is not that I can't set up a shot (within the limits of remembering all the features of the meter). I think mcgregni's point was providing the convenience of P-TTL to exterior fill-flash shots; and my extension of that point is considering how to do this with old-time TTL.

[As an aside, hasn't someone by now come up with a widely recognized unambiguous abbreviation for the original TTL?]

[mcgregni]

I've seen the term "Analogue TTL" used to describe film era 'off the film plane' flash metering systems, whilst 'digital TTL' refers to more recent systems that use the image sensor and multi-segment light metering.

A point was made on my duplicate thread on the Pentax User forum, that TTL flash is only needed for moving subjects. Actually, what I'm trying to say in this regard is that it is not only a subject that might move. Outdoors we may be responding to changing ambient light (eg the sun back light), and changing the flash positioning in relation to a subject, say in order to change framing to exclude something in a background, or simply to respond to a different sized subject (such as my kids, who all need different placement of the diffusers).

So, an automatic dynamic response with flash exposures can be beneficial outdoors generally, not only with moving subjects.

[kaseki]

OK, I think this can be done with A-TTL on the 645N with AF500FTZ. First, to review the general (static background illumination case) here is someone's suggested procedure for daylight balanced fill flash. (Sorry, but I don't have the provider's name on my crib sheet.)

1. Set camera to [metered] manual mode
2. Set shutter speed to 1/60 second or longer
3. Set the counterpart ambient light level aperture per reading of the internal or an external flash meter [of the background] [this could be set to be deliberately underexposed]
4. Turn on the flash unit
5. Set exposure compensation dial on the camera to -1.5 or as desired [I'm not sure what should be desired here]
6. Flash is controlled by exposure compensation and camera by manual settings.

What to do when the sunlight background is varying? I think step 1 needs to be shutter priority AE mode instead of manual mode, and there may have to be some playing with the selected shutter speed to keep the auto aperture within the range available from the lens over the changing lighting conditions. However, auto aperture use may preclude keeping the background less bright than normal exposure would achieve when a darker background is desired.

I haven't tried either of these schemes yet, so it will be interesting to see what results.

[mcgregni]

I carried out some tests today trying out a hair light with TTL, and I was very impressed. I popped a teddy bear up on a sofa back and placed a flash behind, about 3 ft back, aiming at the head. The settings were ISO 400, F8, 1/180th, and in Manual mode I needed 1/16th power to light up the rim of the head nicely, with highlights about 60% along the histogram. Switching to TTL mode, the exact same brightness was achieved with a setting of -0.5 stop.

Considering that the hairlight was only a rim around a teddies head, and that the majority of the frame was darkness, I though the metering was quite extraordinary. Adjustments of half stops up and down produced perfectly reliable and consistent steps of brightness changes, again quite amazing for automatic flash metering I think!

Introducing a main light from the softbox in front had no impact on the independence of the rim light at all .... both groups were completely controllable independently. It was just like working in manual mode, but in 'stops'. Very impressed.