[stevebrot]

whichever has a trailing sync pulse, or else you're making your own by putting a buffer inline between camera and flash to delay the firing signal.

There is no such camera that works with a non-dedicated flash, AFAIK. I was hoping you might. As for a delay...that sounds suspiciously like what I suggested above.

also here's a troubleshooting thread about the cactus v6ii wherein people having trouble with TTL second-curtain sync point out that manual second-curtain sync works fine so now we know that works.

Does not work with generic flash and with Pentax, my understanding is that a Pentax-compatible dedicated flash must be used as the remote. That is basically similar to using a P-TTL flash on the camera to relay the sync optically, though the latter is potentially much cheaper.


Steve

[johnha]

How about a older, non-P-TTL flash with 2nd curtain sync - something like an AF240FT to slave trigger the studio flash? Firing it in Manual Low power (GN approx. 6m) - would that work?

[spinach]

Does not work with generic flash and with Pentax, my understanding is that a Pentax-compatible dedicated flash must be used as the remote

the cactus will fire whatever you connect to it, if it's worth a quarter.

There is no such camera that works with a non-dedicated flash, AFAIK.

nikons fire the second curtain pulse on center pin and sync port, and so work with every flash. if you're using cactus, a pentax transmitter to nikon receivers would be your guy.

[stevebrot]

nikons fire the second curtain pulse on center pin and sync port, and so work with every flash. if you're using cactus, a pentax transmitter to nikon receivers would be your guy.

Cool...I wondered about Nikon. The camera manuals are coy about supported flash and the rear-curtain flash tutorials I found were specific to iTTL. As for Cactus v6ii configured as Pentax-local and Nikon remote...I dunno. The Cactus documentation is not clear whether Pentax rule of 2nd-curtain sync as P-TTL feature can be spoofed from a remote Nikon protocol flash.

How about a older, non-P-TTL flash with 2nd curtain sync - something like an AF240FT to slave trigger the studio flash? Firing it in Manual Low power (GN approx. 6m) - would that work?

Got me! I know that Speedlight S2 optical trigger from P-TTL flash will work for 2nd curtain sync, but not having an FT-series flash to test with, I can't say for sure except to parrot the conventional line that current model Pentax cameras won't cooperate with FT-series flash except as non-dedicated manual flash and that 2nd-curtain sync is TTL only on those flash.


Steve

[spinach]

The Cactus documentation is not clear whether Pentax rule of 2nd-curtain sync as P-TTL feature can be spoofed from a remote Nikon protocol flash.

you wouldn't be using pentax ttl, you'd be shooting manually. which was done in the troubleshooting thread i linked, wherein people complained about Only being able to fire second-curtain in manual mode.

[mcgregni]

The V6II only offers 2nd Curtain Sync with the X-TTL firmware, and this requires a P-TTL (Pentax dedicated system) flash type, or a Cactus RF60/x. There is 2nd curtain available in both TTL and M modes .....however there is no "cross-brand" compatibility, so Nikon flashes are not supported.

[stevebrot]

you wouldn't be using pentax ttl, you'd be shooting manually. which was done in the troubleshooting thread i linked, wherein people complained about Only being able to fire second-curtain in manual mode.

The V6II only offers 2nd Curtain Sync with the X-TTL firmware, and this requires a P-TTL (Pentax dedicated system) flash type, or a Cactus RF60/x. There is 2nd curtain available in both TTL and M modes .....however there is no "cross-brand" compatibility, so Nikon flashes are not supported.

User mcgregni was active in the linked thread as was user @Class_A. I do believe they know how this works. My understanding is that in Pentaxland, 2nd-curtain sync is a feature of P-TTL. One can map the remote flash (RX) to Nikon manual, but since the Pentax side (TX) does not support manual flash 2nd-curtain sync, one cannot expect magical translation to a Nikon body feature. Nothing in the chain is telling the camera that a P-TTL flash is asking for 2nd-curtain sync and nothing on the RX side is prepared to accept it if it comes.*


Steve

* To be honest, I doubt that the body actually sends the sync. I suspect that the body sends its settings and lets the flash figure out the details once the pre-flash is calculated.

[spinach]

The V6II only offers 2nd Curtain Sync with the X-TTL firmware, and this requires a P-TTL (Pentax dedicated system) flash type, or a Cactus RF60/x. There is 2nd curtain available in both TTL and M modes .....however there is no "cross-brand" compatibility, so Nikon flashes are not supported.

v6ii in that troubleshooting thread has 2nd curtain in ttl and manual – people use it and describe their tests there.

no cross-brand on cactus’ own environment sounds fake, even yongnuo doesn’t care if you use their canon remote to fire a nikon trigger long as they’re both in the 602 or 603 series.

---------- Post added 06-27-18 at 10:12 AM ----------

since the Pentax side (TX) does not support manual flash 2nd-curtain sync,

the troubleshooting thread i linked has people firing second curtain in manual, and in fact complaining that’s All they can do, with flashes supporting P-TTL. if the pop is happening only on manual and not on TTL (they describe getting only preflash and first curtain), that suggests the two are different processes.

I suspect that the body sends its settings and lets the flash figure out the details once the pre-flash is calculated.

that’s not happening instantaneously on two pins over radio. also, through the lens meansthrough the lens – the camera sends start and stop after determining when there’s enough light.

[stevebrot]

v6ii in that troubleshooting thread has 2nd curtain in ttl and manual – people use it and describe their tests there.

no cross-brand on cactus’ own environment sounds fake, even yongnuo doesn’t care if you use their canon remote to fire a nikon trigger long as they’re both in the 602 or 603 series.

---------- Post added 06-27-18 at 10:12 AM ----------


the troubleshooting thread i linked has people firing second curtain in manual, and in fact complaining that’s All they can do, with flashes supporting P-TTL. if the pop is happening only on manual and not on TTL (they describe getting only preflash and first curtain), that suggests the two are different processes.


that’s not happening instantaneously on two pins over radio. also, through the lens meansthrough the lens – the camera sends start and stop after determining when there’s enough light.

Evidence would be nice. Can you provide a photo you have taken with your recent model Pentax dSLR + cactus v6II + speedlight kit showing 2nd curtain sync? Full details please and OOC JPEG with no PP please. I know that sounds a little short, but perhaps you are not aware that user @mcgregni literally wrote the book on flash with current Pentax product. User @Class_A is this site's unofficial Cactus ambassador and resident expert on all things Cactus. With any luck, perhaps he will drop in too. I would love to be proven wrong on this, me being mostly a dabbler in this space, but one who generally knows his gear. Perhaps both mcgregni and I are not up to date and Cactus has done some additional magic.

BTW...I don't believe anyone on the thread you linked to successfully did 2nd curtain sync without either a P-TTL or Cactus RF60X on the receiving end. In addition, Cactus documentation is explicit regarding the limitations of their Pentax implementation.

Steve

[stevebrot]

that’s not happening instantaneously on two pins over radio. also, through the lens meansthrough the lens – the camera sends start and stop after determining when there’s enough light.

That last phrase is quite telling and might explain the huge disconnect.


Steve

[mcgregni]

That thread over at Cactus was about a firmware bug, and Cactus fixed it in an update. Looking at it again, it appears to be entirely about the X-TTL firmware. As was stated in that thread, 2nd curtain sync is a subset of the X-TTL firmware, and the Pentax version of that does not offer Cross-Brand flash compatibility. The RF60x offers an economical route into off-camera P-TTL / HSS / 2nd Curtain Sync combined with the V6II Tx (built in receivers in the RF60x), and you get both Manual and TTL mode 2nd Curtain Sync.

For manual strobes you might be able to use a trigger that allows a delay setting, and work it out yourself as needed. Obviously more effort than automatic syncing . There are new studio strobe products out from Cononmark and Photix with P-TTL, so it might be worth finding out if they offer automatic 2nd curtain sync.

[johnha]

I've tested my K-5 (I don't have a more modern body) with my AF240FT - it triggers rear curtain sync (when using the rear curtain switch on the gun) when set to 'TTL' (seems to fully discharge the flash) or Manual High (full) & Low (quarter) power. Tested by a 4 second exposure in manual so you can easily see the flash firing just before the shutter closes.