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08-25-2017, 05:02 AM   #1
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Second curtain sync YN 560tx + YN 560 IV on Pentax k5 II

Hi everyone,
I do have a question on the above mentioned flash set.
I've just purchased both the flash and the transmitter (canon version) and everything works smoothly so far.
However, I've tried to sync on the second curtain from the camera menu and that doesn't work. The off camera speed light keeps flashing on the first curtain.
Am I missing something?
On the specific shot I was trying do I solved doing it "backwards" because it was a moving person, but that won't be always the case.
Can I sync on second curtain?



08-25-2017, 05:08 AM   #2
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My expectation with that Yongnuo combination is that 2nd Curtain Sync is only possible with the flash on camera. Using another Wireless P-TTL flash on camera as controller or master should allow the usual off camera features. Or a "Radio P-TTL" trigger system, like Acon.

Last edited by mcgregni; 08-25-2017 at 11:53 AM.
08-25-2017, 05:23 AM   #3
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Well I've always thought that second curtain sync was a camera feature that simply would fire the signal in a different moment, so the transmitter would have as well.. Isn't that the case?

08-25-2017, 05:43 AM   #4
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The Yongnuo manual isn't exactly clear on the subject but says something about rear curtain only working on Canon.

08-25-2017, 07:08 AM   #5
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QuoteOriginally posted by marcob8986 Quote
Well I've always thought that second curtain sync was a camera feature that simply would fire the signal in a different moment
Not really - in case of K-S2 / 540FGZ combo you have to set second curtain in flash, not in camera.
08-25-2017, 09:15 AM   #6
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The sync mode is a subset of P-TTL, and so requires a P-TTL accessory control flash or P-TTL radio trigger system to operate the slave flash in 2nd Curtain mode and correctly sync with the exposure.

Last edited by mcgregni; 08-25-2017 at 12:05 PM.
08-25-2017, 11:58 AM   #7
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Just to add, in case of confusion, the 2nd Curtain Sync mode on the cameras only applies to the built-in flash .....2nd Curtain plus wireless modes with the built-in flash simultaneously isn't possible. For wireless operation then set 2nd Curtain sync on the controller /master accessory flash. It may or may not be needed also on the Yongnuo slave ... This probably has to be tested to find out.

Last edited by mcgregni; 08-25-2017 at 12:04 PM.
08-26-2017, 08:13 AM   #8
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Sorry, but here's a few more 2nd Curtain Sync ponderings ..... this question has, as so often with these sort of intricate compatibility matters, got me thinking over it all again ......


I realise that the issue of 2nd Curtain Sync in Wireless mode is really not well documented, not in the Pentax Manuals and not in detail in my Guide either. So its a good candidate for a re-think, and I will certainly provide the needed information in the next Guide update!


A flick through the Flash Manuals for the two Pentax '540' models reveals precious little of any use relating to 2nd Curtain Sync plus Wireless


Also I had a look at both the K5 and K3 Manuals ..... The K5 Manual, on Page 194 (within the "Wireless Shooting" section) has this paragraph ....
"Trailing Curtain Sync
When using the built-in flash with an external flash (AF540FGZ or AF360FGZ) that is set to the Trailing Curtain Sync mode, the built-in flash will also use this mode. "



This seems odd ..... optical communications are one-way, from controller to slave. Therefore how could any setting made on the slave be communicated back to the controller? Plus there is no optical sensor on the camera. And finally, Trailing Curtain sync mode cannot be set on an accessory flash that is in Slave mode.


This passage does not appear in the K3 manual .... perhaps also subsequent manuals. What do we think about this?


I did some test to confirm everything, and this is how it is :


When a Pentax flash is set to 'Slave Mode' (ie it is to function off-camera), then no Sync modes can be set simultaneously on that Slave (the flash remains stuck in leading curtain sync mode). The required sync modes for Wireless operation need to be set on the 'control / master' accessory flash (eg 2nd Curtain, HSS) ..... the sync mode set is transmitted during the Pre-Flash to the slave. Therefore for both HSS and 2nd Curtain then just leave the Slave flash set to Wireless P-TTL (slave) and set the sync mode on the control flash.


This of course rules out the Built-in flash for both of these sync functions, because HSS is not offered and 2nd Curtain cannot be set simultaneously with Wireless mode. So we need an accessory P-TTL flash on the camera for these wireless sync modes to operate.


Of course, in this thread the OPs particular problem is that he is using a radio trigger that is dedicated to the Canon system .... it is just incompatible with Pentax P-TTL and so cannot transmit the sync mode to the flash. I believe that a 'Radio P-TTL' trigger system, such as Aokatek or Acon (and Cactus soon once the XTTL firmware comes out) would be needed for Rdaio control and 2nd curtain sync off-camera.

09-24-2017, 01:08 PM   #9
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I own the YN560III (not YN560IV as in the original post), but can offer that a semblance of 2nd curtain sync is quite possible using a method similar to that proposed by @mcgregni above.
  • On-camera (or built-in) flash set to 2nd-curtain (aka trailing/back curtain) sync
  • YN560xx set to S2 optical slave
Now the BIG caution. The timing of second curtain sync may not be as expected. Many believe that second curtain sync is the opposite of first curtain and occurs at the start of second curtain travel. That won't work since the flash must be finished before the curtain starts its travel. Otherwise there will be partial or full underexposure within the frame. Conversely, fire the flash too soon and there may be motion blur both before and after the moving subject. Ideally, either the camera or the flash must "know" both the flash duration and time for second curtain start in order to properly time the sync.

That is where P-TTL comes in and may be why trailing/2nd-curtain sync requires P-TTL on Pentax cameras.* I don't have hard information on this, but since flash duration (power) for the required exposure may be known after the preflash, the system may be in a position to properly time the preflash. OTOH, it may just take the maximum duration for the slowest of the participating flashes and use that to calculate the sync time. Who knows...

As one might imagine, there is some risk to having a non-participating Yongnuo slave in the mix. If the slave has the same duration as the master, all is good. If shorter, there may be motion blur in front of the subject. If longer, the contribution of the slave may be less than expected. Some experimentation might be in order.**


Steve

* Other brands may offer greater flexibility, but still require that the flash duration and time for second curtain travel be known.
** Maximum duration for the YN560 III/IV is 1/200s. Duration for the various power levels may be calculated from that.

Last edited by stevebrot; 09-24-2017 at 01:19 PM.
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