Optical Triggering of Strobe

ofer4 · 02-13-2018, 08:47 PM

Lighting gurus...

I am making my first foray into studio lighting. I have purchased a simple (non-TTL, non-HSS) 150 Ws strobe. My question here regards optical triggering.

Some cheapo radio triggers are likely in my future. But I'd still like to understand the optical triggering process first. Here's the scoop:

1. Using the on-camera flash (K-30), I can get the strobe to fire through optical triggering. I set the wireless flash mode to control, rather than master. It works, but due to a known issue of the on-board flash timing, some fraction of the on-board flash still appears in the pictures.

2. In order to eliminate issue #1, I mounted my Metz 52 to the hotshoe to use as a trigger. I set the Metz to Control mode. It fires the strobe, but the strobe lighting does not appear in the photo, as though it is firing a pre-flash for p-TTL, even though it's not in TTL mode. So, what gives? I actually thought something might be wrong with the strobe, but putting the Metz in "M" mode works! Of course, the Metz light now appears in the photo, too. I can dial it back to 1/128, which might be fine, but I'd still like to get it to work properly.

So, the short version: Why can I properly trigger the strobe in "M" mode of the hotshoe flash but not in Control mode? How do I optically trigger the strobe without the hotshoe flash also appearing the photo?

Thanks!

sqrrl · 02-13-2018, 09:07 PM

Your other option is to grab some lighting gels in opposing colours (ie deep blue & red, or deep purple & orange) and stack them - with that you should be able to mostly eliminate visible light, though still pass infrared light (lighting gels pass infrared for heat dissipation reasons). The infrared light alone will trigger most opto triggers. I've used stacked gels with a cheap on-hotshoe flash to trigger strobes plenty and found it pretty reliable.

ofer4 · 02-13-2018, 09:14 PM

Thanks, sqrrl. I read that option in another forum and found it rather creative.

I have a pile of gels laying around, so it's certainly an option.

I'm just trying to track down why Control mode doesn't seem to work (or how to make it work). Anybody know?

**macman24054** · 02-14-2018, 04:44 AM

The wireless control mode setting on your camera is meant to work in conjunction with compatible speedlights. Another option is to the on board flash to -2 compensation. If you shoot with your strobe at high enough power this may help. Let us know what you end up finding that works.

ofer4 · 02-14-2018, 08:19 AM

macman, that's essentially the workaround that I've been using, with either the onboard flash or the Metz. And except for a slight addition to the lighting, it works. Still trying to figure out how to get a proper control mode, though...

stevebrot · 02-14-2018, 10:56 AM

Originally posted by ofer4

but due to a known issue of the on-board flash timing, some fraction of
the on-board flash still appears in the pictures.

It is not so much an issue as it is a fact of life. When functioning as a controller, the on-camera flash must, ummm, "control" and this is done with a short second burst from the controlling flash to signal sync and duration. This second burst is required for optical P-TTL triggering (cabled sync being the other option). The second burst is usually quite brief (weak) in controller mode and makes minimal contribution. How much contribution comes from the controller pulse depends on the aperture and ISO settings and whether a compatible P-TTL slave is detected.

Originally posted by ofer4

I have purchased a simple (non-TTL, non-HSS) 150 Ws strobe.

Originally posted by ofer4

I'm just trying to track down why Control mode doesn't seem to work (or how to make it work). Anybody know?

The key is that control mode is used to "control" a P-TTL slave. Your strobe, OTOH, does not "talk" P-TTL. It fires when it detects a flash, any flash. If your strobe is configured to ignore pre-flash, it will be triggered by the second pulse from a P-TTL master operating in either master or controller mode. Otherwise, it will fire from the first flash event it senses.

Your options if you want minimal or zero contribution from the on-board flash run like this:

Use M mode for the on-board flash set to lowest setting with the strobe configured to fire as a normal slave (usually SL1 mode). ND filters for the flash might also be appropriate. --OR--
Set the on-board flash to operate as P-TTL controller and the strobe to ignore the pre-flash (usually SL2).* ND filters for the flash might be required. --OR--
Use a combination of shield/reflector to prevent the on-board flash from illuminating the subject while still triggering the slave --OR--
Use filters or similar (Nikon SG-31R?) on the triggering flash to prevent all but IR light from passing --OR--
Ditch the on-board flash and move to a wireless (RF) trigger or wired sync

Good luck

P.S. Perhaps @mattdm will drop in on this thread. He is the respondent on the thread you linked to above.

Steve

* Some flash/strobes have too short a delay in SL2 mode and fire from the tail end of the fairly bright pre-flash (slave flash/strobe fires too soon) with unpredictable results.

ofer4 · 02-14-2018, 10:53 PM

Thanks, Steve!

It sounds as though part of my problem is conceptual, then. I was under the impression that Control mode was solely designed to fire the external flash without the trigger flash appearing in the photo. I didn't know that it is inherently connected to p-TTL and always carries a pre-flash. I'm actually surprised that a "Manual Control" option (really just a flash, but properly timed) isn't present. Who knew?

The Metz that I'm using, if I understand things correctly, should handle the pre-flash correctly if it is used externally (no strobe). This distinction should provide a definitive test for me since the Metz is smarter than the strobe.

Great info, everyone!

**clackers** · 02-14-2018, 11:19 PM

Originally posted by ofer4

Thanks, Steve!

It sounds as though part of my problem is conceptual, then. I was under the impression that Control mode was solely designed to fire the external flash without the trigger flash appearing in the photo.

The issue is that the flash doesn't just switch off, its brightness decays, and there can be some left over when the shutter opens.

You wouldn't notice this outdoors, but up close inside with higher ISO or whatever, sure.

Indoors you can often bounce the trigger flash rather than point it at the subject.

02-14-2018, 10:56 AM	#6
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by ofer4 but due to a known issue of the on-board flash timing, some fraction of the on-board flash still appears in the pictures. It is not so much an issue as it is a fact of life. When functioning as a controller, the on-camera flash must, ummm, "control" and this is done with a short second burst from the controlling flash to signal sync and duration. This second burst is required for optical P-TTL triggering (cabled sync being the other option). The second burst is usually quite brief (weak) in controller mode and makes minimal contribution. How much contribution comes from the controller pulse depends on the aperture and ISO settings and whether a compatible P-TTL slave is detected. Originally posted by ofer4 I have purchased a simple (non-TTL, non-HSS) 150 Ws strobe. Originally posted by ofer4 I'm just trying to track down why Control mode doesn't seem to work (or how to make it work). Anybody know? The key is that control mode is used to "control" a P-TTL slave. Your strobe, OTOH, does not "talk" P-TTL. It fires when it detects a flash, any flash. If your strobe is configured to ignore pre-flash, it will be triggered by the second pulse from a P-TTL master operating in either master or controller mode. Otherwise, it will fire from the first flash event it senses. Your options if you want minimal or zero contribution from the on-board flash run like this: Use M mode for the on-board flash set to lowest setting with the strobe configured to fire as a normal slave (usually SL1 mode). ND filters for the flash might also be appropriate. --OR-- Set the on-board flash to operate as P-TTL controller and the strobe to ignore the pre-flash (usually SL2).* ND filters for the flash might be required. --OR-- Use a combination of shield/reflector to prevent the on-board flash from illuminating the subject while still triggering the slave --OR-- Use filters or similar (Nikon SG-31R?) on the triggering flash to prevent all but IR light from passing --OR-- Ditch the on-board flash and move to a wireless (RF) trigger or wired sync Good luck P.S. Perhaps @mattdm will drop in on this thread. He is the respondent on the thread you linked to above. Steve * Some flash/strobes have too short a delay in SL2 mode and fire from the tail end of the fairly bright pre-flash (slave flash/strobe fires too soon) with unpredictable results. Last edited by stevebrot; 02-14-2018 at 11:24 AM.

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02-13-2018, 08:47 PM	#1
ofer4 Veteran Member Join Date: Jun 2011 Location: Utah Posts: 428	Optical Triggering of Strobe Lighting gurus... I am making my first foray into studio lighting. I have purchased a simple (non-TTL, non-HSS) 150 Ws strobe. My question here regards optical triggering. Some cheapo radio triggers are likely in my future. But I'd still like to understand the optical triggering process first. Here's the scoop: 1. Using the on-camera flash (K-30), I can get the strobe to fire through optical triggering. I set the wireless flash mode to control, rather than master. It works, but due to a known issue of the on-board flash timing, some fraction of the on-board flash still appears in the pictures. 2. In order to eliminate issue #1, I mounted my Metz 52 to the hotshoe to use as a trigger. I set the Metz to Control mode. It fires the strobe, but the strobe lighting does not appear in the photo, as though it is firing a pre-flash for p-TTL, even though it's not in TTL mode. So, what gives? I actually thought something might be wrong with the strobe, but putting the Metz in "M" mode works! Of course, the Metz light now appears in the photo, too. I can dial it back to 1/128, which might be fine, but I'd still like to get it to work properly. So, the short version: Why can I properly trigger the strobe in "M" mode of the hotshoe flash but not in Control mode? How do I optically trigger the strobe without the hotshoe flash also appearing the photo? Thanks!

02-13-2018, 09:07 PM	#2
sqrrl Veteran Member Join Date: Mar 2017 Location: Otago, New Zealand Posts: 422	Your other option is to grab some lighting gels in opposing colours (ie deep blue & red, or deep purple & orange) and stack them - with that you should be able to mostly eliminate visible light, though still pass infrared light (lighting gels pass infrared for heat dissipation reasons). The infrared light alone will trigger most opto triggers. I've used stacked gels with a cheap on-hotshoe flash to trigger strobes plenty and found it pretty reliable.

02-13-2018, 09:14 PM	#3
ofer4 Veteran Member Join Date: Jun 2011 Location: Utah Posts: 428 Original Poster	Thanks, sqrrl. I read that option in another forum and found it rather creative. I have a pile of gels laying around, so it's certainly an option. I'm just trying to track down why Control mode doesn't seem to work (or how to make it work). Anybody know?

02-14-2018, 04:44 AM	#4
macman24054 Loyal Site Supporter Join Date: Aug 2013 Location: Axton, VA Photos: Gallery \| Albums Posts: 461	The wireless control mode setting on your camera is meant to work in conjunction with compatible speedlights. Another option is to the on board flash to -2 compensation. If you shoot with your strobe at high enough power this may help. Let us know what you end up finding that works.

02-14-2018, 08:19 AM	#5
ofer4 Veteran Member Join Date: Jun 2011 Location: Utah Posts: 428 Original Poster	macman, that's essentially the workaround that I've been using, with either the onboard flash or the Metz. And except for a slight addition to the lighting, it works. Still trying to figure out how to get a proper control mode, though...

02-14-2018, 10:53 PM	#7
ofer4 Veteran Member Join Date: Jun 2011 Location: Utah Posts: 428 Original Poster	Thanks, Steve! It sounds as though part of my problem is conceptual, then. I was under the impression that Control mode was solely designed to fire the external flash without the trigger flash appearing in the photo. I didn't know that it is inherently connected to p-TTL and always carries a pre-flash. I'm actually surprised that a "Manual Control" option (really just a flash, but properly timed) isn't present. Who knew? The Metz that I'm using, if I understand things correctly, should handle the pre-flash correctly if it is used externally (no strobe). This distinction should provide a definitive test for me since the Metz is smarter than the strobe. Great info, everyone!

02-14-2018, 11:19 PM	#8
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	Originally posted by ofer4 Thanks, Steve! It sounds as though part of my problem is conceptual, then. I was under the impression that Control mode was solely designed to fire the external flash without the trigger flash appearing in the photo. The issue is that the flash doesn't just switch off, its brightness decays, and there can be some left over when the shutter opens. You wouldn't notice this outdoors, but up close inside with higher ISO or whatever, sure. Indoors you can often bounce the trigger flash rather than point it at the subject.