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06-27-2020, 09:19 PM   #1
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5P sync - PTTL only?

Does anyone know from experience if 5P sync between a K-30 and a af540fgz normally displays PTTL as the only available mode besides spot beam? During some testing today, I found that to be the case, but needed more light from the flash than what PTTL would provide even with +1 exp compensation.


I'm ideally trying to fire the flash on M mode at full power using trailing curtain sync, which seems like a very simple request technically from the equipment. The reason I can't just use the hot shoe is that this process also involves the O-GPS 1, and I have the hot shoe adapter F underneath it. I haven't been able to find any details in the manuals that clearly defined this not to be possible. At this point I'm thinking of going: Adapter F -> 5P cable -> adapter F -> cheap remote trigger and then adding the receiver under the flash. It's a fine backup since a remote system only allows M mode rather than any TTl, but I'd rather use only the pentax items for reliability.


Let me know if any of you have experience with this or general thoughts! And if this has been hashed out in other threads, please feel free to help with a link - I didn't have luck searching.

06-27-2020, 10:29 PM - 1 Like   #2
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QuoteOriginally posted by Frogdog Quote
5P sync - PTTL only?
Use of the 5P cable supports the same features as if the flash were on the camera. Where things get strange is if one attempts to use the pass-through hot shoe on the Adapter F at the same time. The contacts are in common between the two and compatibility with the O-GPS and a flash is unlikely. Likewise, trailing curtain flash with a Pentax dSLR is not possible without P-TTL (AF540FGZ manual p65).


Steve

Last edited by stevebrot; 06-27-2020 at 11:49 PM. Reason: Added manual page
06-28-2020, 12:06 AM   #3
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QuoteOriginally posted by Frogdog Quote
I'm ideally trying to fire the flash on M mode at full power using trailing curtain sync, which seems like a very simple request technically from the equipment. The reason I can't just use the hot shoe is that this process also involves the O-GPS 1, and I have the hot shoe adapter F underneath it. I haven't been able to find any details in the manuals that clearly defined this not to be possible. At this point I'm thinking of going: Adapter F -> 5P cable -> adapter F -> cheap remote trigger and then adding the receiver under the flash. It's a fine backup since a remote system only allows M mode rather than any TTl, but I'd rather use only the pentax items for reliability.
Question....Taking my cue from use of the O-GPS; how long is your anticipated exposure? If rather long, it may be possible to do a manual discharge of the flash (hand-held or using a remote trigger) just short of the end of exposure. This approach is very common with light painters.


Steve
06-28-2020, 06:01 AM   #4
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QuoteOriginally posted by stevebrot Quote
Use of the 5P cable supports the same features as if the flash were on the camera. Where things get strange is if one attempts to use the pass-through hot shoe on the Adapter F at the same time. The contacts are in common between the two and compatibility with the O-GPS and a flash is unlikely. Likewise, trailing curtain flash with a Pentax dSLR is not possible without P-TTL (AF540FGZ manual p65).


Steve
Thanks for all the input Steve! Can you clarify on the point you made here? : " Where things get strange is if one attempts to use the pass-through hot shoe on the Adapter F at the same time. The contacts are in common between the two and compatibility with the O-GPS and a flash is unlikely."


This is my first experience using the adapter F and I was under the impression that it passes full functionality through the pins - somewhere in the K30 manual I thought I remember reading general flash functionality was possible without notes defining any restrictions while using the O-GPS - I kind of ran with it from there. I honestly may have read that within the K70 manual when I was researching which model to start out with.


Maybe it was mainly an issue of trailing curtain setting? I can't remember all the variations I tried, but again thank you for taking the time to find and reference that page number within the af540fgz manual.


And your other question : "Question....Taking my cue from use of the O-GPS; how long is your anticipated exposure? If rather long, it may be possible to do a manual discharge of the flash (hand-held or using a remote trigger) just short of the end of exposure. This approach is very common with light painters."

Exposures are anywhere from 30 sec to a couple of minutes, and I am moving in the direction of doing exactly what you're suggesting here.


Thanks again!!
Austin

06-28-2020, 02:57 PM   #5
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QuoteOriginally posted by Frogdog Quote
Can you clarify on the point you made here? : " Where things get strange is if one attempts to use the pass-through hot shoe on the Adapter F at the same time. The contacts are in common between the two and compatibility with the O-GPS and a flash is unlikely."

This is my first experience using the adapter F and I was under the impression that it passes full functionality through the pins - somewhere in the K30 manual I thought I remember reading general flash functionality was possible without notes defining any restrictions while using the O-GPS - I kind of ran with it from there. I honestly may have read that within the K70 manual when I was researching which model to start out with.
Glad to be of service!

In regards to the Hot-Shoe Adapter F, the 5P sync cord F, and the Off-Camera Shoe Adapter F when used together; the shoe contacts for both adapters are wired in parallel to the foot contacts of the Hot-Shoe Adapter F. While both are true pass-through, the circuits are not isolated. The lack of isolation has implications, the nature of which devices share the circuits.

Example #1 | Center (sync) contact
There is a common side-effect when using two flashes having different trigger voltage (example: 6V and 4V), one on the camera adapter and the other on the off-camera adapter. When sync is fired, it is possible only one of the two flashes will fire due to the circuit voltage only dropping low enough to trigger the higher voltage unit while the circuit was closed for sync.

Example #2 | Dedicated "ready" contact
Another problem might be two Pentax-dedicated flash where "ready" might go "high" for the circuit and "ready" being shown in the viewfinder with only one flash actually recharged. This is an issue only when using cameras that support the analog dedication/control protocol such as the Pentax LX film camera.

Example #3 | Digital (data) contact
The potential problem here is one of cross-talk or mixed messages across the digital/data contact. The 5P cables and connectors date back to the digital dedication/TTL protocol where the bulk of the logic was on the camera and communication to the digital contact could be shared and be equally relevant for a long daisy chain of hard-wired off-camera flash TTL flash. That changed with P-TTL where most of the logic is borne by the flash with a fair amount of exchange between flash and camera. If more than one flash is used per control circuit (the built-in flash has its own), the intent is that communication be done through optical wireless with one master. Moving from flash to the O-GPS, that unit is in intimate continuous communication to control the image sensor position. I don't own an O-GPS to test with, but unless there is provision to ignore or turn off the source of other signals, potential for interference definitely exists. I would use strong caution if attempting mixed O-GPS and P-TTL communication on the same digital contact circuit (i.e. both on the same 5P cable).

I hope you share this project and its outcome. Something tells me you have something interesting in mind.


Stee
06-28-2020, 08:04 PM   #6
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QuoteOriginally posted by stevebrot Quote
Glad to be of service!

In regards to the Hot-Shoe Adapter F, the 5P sync cord F, and the Off-Camera Shoe Adapter F when used together; the shoe contacts for both adapters are wired in parallel to the foot contacts of the Hot-Shoe Adapter F. While both are true pass-through, the circuits are not isolated. The lack of isolation has implications, the nature of which devices share the circuits.

Example #1 | Center (sync) contact
There is a common side-effect when using two flashes having different trigger voltage (example: 6V and 4V), one on the camera adapter and the other on the off-camera adapter. When sync is fired, it is possible only one of the two flashes will fire due to the circuit voltage only dropping low enough to trigger the higher voltage unit while the circuit was closed for sync.

Example #2 | Dedicated "ready" contact
Another problem might be two Pentax-dedicated flash where "ready" might go "high" for the circuit and "ready" being shown in the viewfinder with only one flash actually recharged. This is an issue only when using cameras that support the analog dedication/control protocol such as the Pentax LX film camera.

Example #3 | Digital (data) contact
The potential problem here is one of cross-talk or mixed messages across the digital/data contact. The 5P cables and connectors date back to the digital dedication/TTL protocol where the bulk of the logic was on the camera and communication to the digital contact could be shared and be equally relevant for a long daisy chain of hard-wired off-camera flash TTL flash. That changed with P-TTL where most of the logic is borne by the flash with a fair amount of exchange between flash and camera. If more than one flash is used per control circuit (the built-in flash has its own), the intent is that communication be done through optical wireless with one master. Moving from flash to the O-GPS, that unit is in intimate continuous communication to control the image sensor position. I don't own an O-GPS to test with, but unless there is provision to ignore or turn off the source of other signals, potential for interference definitely exists. I would use strong caution if attempting mixed O-GPS and P-TTL communication on the same digital contact circuit (i.e. both on the same 5P cable).

I hope you share this project and its outcome. Something tells me you have something interesting in mind.


Stee
More great info, Steve! I will have to screenshot your post to save for future reference regarding potential interference scenarios.


I'll gladly share sample images when I produce something share-worthy. There was moderate success this morning in manually firing the flash near the end of a 1.5 minute exposure while the O-GPS was working. I didn't notice any issues but lots more testing to do.

The chain went: camera hot shoe -> adapter F with OGPS on top shoe -> 5p cable (5pL, - wrong choice of length after all?) -> adapter F with radio trigger attached - -> receiver and af540fgz on M 1/1


Timing with my phone, fired 2 full power blasts as near to each other as recycling allowed at the end of exposure - results were fine. This is during the daytime, so I use a Lee big stopper for sufficiently long exposure. I am sort of hoping for some night time work I can just use the 5p straight to flash and use PTTL since I wouldn't necessarily need the same amount of total light output.


Thanks again! I'll come back to report any other relevant quirks, failures, or successes

Austin
06-28-2020, 10:49 PM   #7
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QuoteOriginally posted by Frogdog Quote
The chain went: camera hot shoe -> adapter F with OGPS on top shoe -> 5p cable (5pL, - wrong choice of length after all?) -> adapter F with radio trigger attached - -> receiver and af540fgz on M 1/1
Question...why bother with the 5P components? The radio TX should not need to be in circuit with the camera.


Steve
06-29-2020, 08:08 AM   #8
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QuoteOriginally posted by stevebrot Quote
Question...why bother with the 5P components? The radio TX should not need to be in circuit with the camera.


Steve
Good question! And a simple answer is I probably won't - I'll test to double check with my specific radio units but I'm sure you're right.

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