[kaseki]

Attempting to understand Cactus V6II capability from what I have read at their website and here leaves me with a couple of specific questions. Hence, below I have constructed two scenarios from which I hope to better understand Cactus V6II capability:

(Scenario A) Portrait or still-life photography in a "studio" using a number of AF-500FTZ TTL- and manual-capable flashes and a 645N (TTL) film camera. The flashes are aimed at umbrellas, diffusers, or whatever and manually adjusted to achieve the desired ratios of lighting on the target and/or its background. One flash is the master, the other slaves. In the case of the AF-500GTZ, each slave can react to the master flash with its own flash. Measurement at the target (by a Flash Meter IV, say) with all flashes operational reveals the aperture that should be used for proper exposure. If a different aperture is desired for any of the usual reasons, all of the flashes will have to be manually adjusted until the ratios are correct and the measurement shows that the desired aperture is appropriate.

It would be convenient to be able to use TTL on all flashes to allow setting a desired aperture without rescaling all the flashes. Question A: Can an array of Cactus V6II units used at the camera and at each of the dispersed flashes extend TTL to all of the flashes; that is, quench them all together when enough light for the aperture and film speed has reached the TTL sensor?

(Scenario B) Same configuration as Scenario A except the camera is a 645Z (P-TTL) focal-plane array digital camera. Question B: Can the Cactus V6II use the multiflash capability of the AF-500FTZ flashes to simulate P-TTL on all flashes at once, thereby satisfying the light input needed by the P-TTL sensing circuitry in the digital camera?

Thanks.

---

Last edited by kaseki; 02-16-2018 at 07:46 PM. Reason: GTZ should be FTZ

[pschlute]

I cannot answer either of your questions directly but if your flashguns are capable of being triggered by the V6II units you can adjust up to four "groups" directly from the TX unit on your camera hotshoe from 1/1 to 1/128 in 1/3 stop increments. Much easier than walking round to each flashgun. But the Cactus units use the P-TTL protocol to trigger the flashguns even when the Cactus are in manual mode. Yours are not P-TTL units so they may not work in the same fashion.

I use AF540FGZ and AF360FGZ and it works fine as these are P-TTL flashguns and can be operated in the way i described above (manual flash output controlled by the V6II unit) or in P-TTL mode (TTL set on the Cactus unit).

There is a problem however if I want to use a flashmeter. Because the cactus uses the P-TTL protocol, a preflash is produced even in manual mode and the Pre flash fools the meter. I resort in this case to setting the flashguns to manual mode so no preflash is emitted. But this does mean that i can not now use the cactus unit on the hotshoe to control the power output and have to resort to adjusting each flashgun directly.

But your main issue will be if they will work at all with your flash units.

Hope this helps a bit

[UncleVanya]

The af-500ftz isn't compatible with the cactus v6 or v6ii.

Af500ftz and cactus v6? - PentaxForums.com

[kaseki]

Thank you both for clarifying this for me. Looks like I'll have to stick with the manual approach to flash level control. Note that the AF-500FTZ also operates in the TTL mode with the 645N, contrary to the link given above and page 10 of the flash's operating manual. (Ref. page 63 et seq. of the 645N Operating Manual.)

[stevebrot]

I ran across this old comment that sounds similar to what you are wanting to do. The solution there was to use Cactus driven manual flashes to provide "ambient" with P-TTL serving as the primary flash illumination.

Yongnuo YN560-TX Wireless Flash Controller vs Cactus - Page 3 - PentaxForums.com (Ignore the thread title)


Steve

[mcgregni]

Despite coming around to Awaldram's way of thinking there previously, I now feel that it's best to stick with a traditional definition of "ambient" light (a continuous source, the exposure value being a factor of the exposure time). In the example there of a mixed radio manual/P-TTL setup it was pointed out that the manual flash light did not affect the flashmetering of the automatic flash exposure.

The manual flashes were being used to illuminate the background or surrounds, but on the sensor their effect is as a 'flash exposure', not an ambient one.

[kaseki]

Well, the link provides an entire study program for P-TTL, which I hope to engage more deeply later today. Please note that I don't have a 645Z at present so my emphasis is understanding limitations on TTL in the context of the 645N.

In my view, the word ambient should be reserved for the natural light (and normal interior lighting) as the word has been applied for decades of electro-optical and photo-optical activities. Maybe pseudo-ambient would clarify what the background flashes are effectively accomplishing. Or maybe not.

I have experimented using a AF-140C ring flash in TTL mode with AF-500FTZ flashes in slave mode providing pseudo-ambient lighting (in addition to whatever additional ambient light was present). Flower close-ups were generally successful, lighting wise. But I still desire some capability such as described in Scenario A above.

Perhaps I have a misunderstanding, but I thought that TTL flashes from the '80s and '90s operated by being triggered by the camera hot shoe, and then flash lamp quenched by another signal on the hot shoe within some 10s of microseconds after flash initiation. I don't see why (with perhaps some buffering circuitry) that same trigger cannot be applied to multiple TTL flashes, and the same quench signal cannot also be applied to the multiple TTL flashes. Maybe there is a device that does this via RF that I am too ignorant to know about, or perhaps I misunderstand the capability of Pentax's flash cabling. Clearly, the camera cannot control multiple TTL flashes individually with different flash durations. Operating all flashes with the same flash duration (dynamically determined by the camera's TTL detector) seems to me to be a feasible capability.

[kaseki]

I should add that it may be that the AF-500FTZ does not actually get a quench signal from the camera, but rather gets ISO, aperture and other information from the camera and does its own quenching from the energy it receives itself via an on-board photodetector. In such a case, there would be no way to quench multiple flashes all at the same time thereby keeping the intended illuminance ratios at the target.

[mcgregni]

The older film era TTL system uses a dedicated light sensor inside the camera that detects sufficient exposure directly "off the film plane". Once detected then the quench signal would be sent through the hotshoe, yes. I'm afraid I have no experience of film era wireless systems, I came to use flash seriously too late in life! Obviously the quench signal could be sent to all the slaves simultaneously, but that would involve additional optical signals during the actual flash duration, so I doubt that would be very reliable

The key difference between P-TTL and earlier TTL and "auto" flash types, is that P-TTL has a pre-determined output level ....pre-determined during the metering phase and then that fixed output is delivered during the exposure. The older systems actually carry out the determining during the actual exposure and their output is not decided in advance, but is determined at the cut-off point, and that's only known at the very last (micro) second.

Anyway, it looks like the answers to both of your questions may be no.....I thought there might be some hope for the AF500 FTZ to he controlled manually with the older V6 units? This is because this technology depends on the older anslogue TTL protocol ....however the V6 system requires the flashes to be set to P-TTL mode, and obviously they don't have that .......

Stevebrot's post contained the most hope, maybe he can clarify whether its worth trying the flashes with V6 units for remote manual control .... ?

[stevebrot]

Perhaps I have a misunderstanding, but I thought that TTL flashes from the '80s and '90s operated by being triggered by the camera hot shoe, and then flash lamp quenched by another signal on the hot shoe within some 10s of microseconds after flash initiation.

That is basically true...see below...

I should add that it may be that the AF-500FTZ does not actually get a quench signal from the camera

Its duration is quenched by the body.

The older film era TTL system uses a dedicated light sensor inside the camera that detects sufficient exposure directly "off the film plane". Once detected then the quench signal would be sent through the hotshoe

Basically, yes.

OTF/sensor TTL flash measures the cumulative exposure* and quenches the flash once enough light has been detected from all sources, both ambient and flash. (Flash duration is determined in real time.) Digital TTL and analog TTL protocols do the same thing only using slightly different means.**

P-TTL, OTOH uses a preflash to calculate flash duration in advance. TTL is pretty much foolproof, but requires a more complex camera. P-TTL, however requires no second meter circuit and also allows for easy support for stuff like trailing curtain sync, HSS, flash EC, and wireless metered flash. Note that multiple flash setups for traditional TTL use wired sync and dedicated cabling.

Stevebrot's post contained the most hope, maybe he can clarify whether its worth trying the flashes with V6 units for remote manual control .... ?

I was just linking to @awaldrum 's previous post and have never tried it myself. This much we do know; the AF500FTZ will be full manual (duration set at the flash) when used with the V6 triggers since the flash does not support analog TTL or digital P-TTL.


Steve

* Not the same as instantaneous scene brightness.

** Analog TTL fires the flash with the center contact while keeping the "mode" pin "low" until exposure is sufficient (passive control). Digital TTL also fires using the center contact, but quenches using an explicit command (active control) through the digital data pin on the hot shoe. Digital TTL protocol is a bit of a misnomer since it is more properly digital dedication protocol that allows the body a fair amount of setup control prior to actual firing.

[kaseki]

That is basically true...see below...

Its duration is quenched by the body.

Basically, yes.

OTF/sensor TTL flash measures the cumulative exposure* and quenches the flash once enough light has been detected from all sources, both ambient and flash. (Flash duration is determined in real time.) Digital TTL and analog TTL protocols do the same thing only using slightly different means.**

P-TTL, OTOH uses a preflash to calculate flash duration in advance. TTL is pretty much foolproof, but requires a more complex camera. P-TTL, however requires no second meter circuit and also allows for easy support for stuff like trailing curtain sync, HSS, flash EC, and wireless metered flash. Note that multiple flash setups for traditional TTL use wired sync and dedicated cabling.

I was just linking to @awaldrum 's previous post and have never tried it myself. This much we do know; the AF500FTZ will be full manual (duration set at the flash) when used with the V6 triggers since the flash does not support analog TTL or digital P-TTL.

Steve

* Not the same as instantaneous scene brightness.

** Analog TTL fires the flash with the center contact while keeping the "mode" pin "low" until exposure is sufficient (passive control). Digital TTL also fires using the center contact, but quenches using an explicit command (active control) through the digital data pin on the hot shoe. Digital TTL protocol is a bit of a misnomer since it is more properly digital dedication protocol that allows the body a fair amount of setup control prior to actual firing.

Excellent clarifications for my understanding. In summary, my present understanding is that the AF-500FTZ is a TTL flash using digital [dedication] TTL protocol and can't be timely quenched via the V6 system.

Is there a link to a description of which pins do what on the Pentax "digital TTL" system?

Pentax once made available a 5-conductor cable for remoting (by a short length) a flash relative to the camera body. As far as I have found so far, no "hubs" were produced for paralleling multiple flashes. Maybe youall know of some. Paralleling might work if the flashes do not respond back to the camera. Otherwise, they would all respond on the same conductor and confusion would result.Success would seem to require that the "hub" would allow only one (master) camera to respond, and the others would be treated as open loop slaves that could still receive the common quench signal.

In any case, thanks

[clackers]

Excellent clarifications for my understanding. In summary, my present understanding is that the AF-500FTZ is a TTL flash using digital [dedication] TTL protocol and can't be timely quenched via the V6 system.

Is there a link to a description of which pins do what on the Pentax "digital TTL" system?

Pentax once made available a 5-conductor cable for remoting (by a short length) a flash relative to the camera body. As far as I have found so far, no "hubs" were produced for paralleling multiple flashes. Maybe youall know of some. Paralleling might work if the flashes do not respond back to the camera. Otherwise, they would all respond on the same conductor and confusion would result.Success would seem to require that the "hub" would allow only one (master) camera to respond, and the others would be treated as open loop slaves that could still receive the common quench signal.

In any case, thanks

If you want TTL, just use modern P-TTL flashes all round and be done with it, Kaseki!

If it's about the cash, buy one decent speedlight as a controller and cheap ones as the slaves.

[Class A]

Question A: Can an array of Cactus V6II units used at the camera and at each of the dispersed flashes extend TTL to all of the flashes; that is, quench them all together when enough light for the aperture and film speed has reached the TTL sensor?

No radio trigger supports analogue TTL in the sense of controlling exposure by means of light reaching "the TTL sensor".

Note that only a couple of early *ist Pentax cameras supported this analogue TTL approach in the digital age. Your 645N film camera supports that approach, but no radio trigger does.

Question B: Can the Cactus V6II use the multiflash capability of the AF-500FTZ flashes to simulate P-TTL on all flashes at once, thereby satisfying the light input needed by the P-TTL sensing circuitry in the digital camera?

Unfortuntely, the AF-500FTZ doesn't support P-TTL so that won't work either.

however the V6 system requires the flashes to be set to P-TTL mode, and obviously they don't have that .......

That's not correct.

The V6 system requires flashes to be set to "TTL" (not "P-TTL") mode. The V6 could remote control the power level of a AF-500FTZ in principle, but sadly the latter is not compatible with the V6. As kaseki stated, the AF-500FTZ appears to support a pure digital TTL protocol (which is not the same as "P-TTL"), whereas the V6 requires the presence of the analogue TTL protocol.

In summary, my present understanding is that the AF-500FTZ is a TTL flash using digital [dedication] TTL protocol and can't be timely quenched via the V6 system.

The V6 definitely cannot remotely control the power level of the AF-500FTZ.

BTW, even if the V6II worked with the AF-500FTZ, you probably wouldn't have wanted it anyhow. A V6II receiver will always cause a pre-flash. When a V6II trigger is used in combination with RF60x units then there won't be a pre-flash unless one is needed (for automatic metering). However, a V6II trigger controlling V6II receivers will always imply a pre-flash, even in the case of pure manual control.

[kaseki]

If you want TTL, just use modern P-TTL flashes all round and be done with it, Kaseki! If it's about the cash, buy one decent speedlight as a controller and cheap ones as the slaves.

Heh. You forgot to include the added cash for a P-TTL capable MF camera body (e.g., 645Z) to replace my one-tenth the cash costing 645N. Given all the various [arguably archaic] TTL flashes I already have, along with a few non-TTL flashes, I think tuning flash radiant intensities via metering is a more economical approach, at least in relatively static "studio" environments.

[stevebrot]

Is there a link to a description of which pins do what on the Pentax "digital TTL" system?

"The K-mount Page" has a good description...

Flash Systems Evolution, Features and Operation | The K-Mount Page

It is not 100% accurate in a couple of areas related to flash/body compatibility*, but does explain the contacts and what they do.


Steve


* The FGZ (non "II") are broadly dedication compatible back to the M-series bodies and support both analogue and digital TTL as well as P-TTL and auto modes (exposure automation using a flash mounted sensor)...the "Swiss Army Knife" of Pentax flashes.