Help, please, with controlling exposure using off-camera flash

Joined
Sep 13, 2007
Messages
19,758
Location
Northern VA suburb of Washington, DC
Equipment
Nikon D7000 camera
Nikon SB-800 off-camera flash unit behind a diffusion panel and facing toward the subject and camera
MJKZZ Water Drop Kit
Subject: Transparent wine glass (chosen because I have so much experience using the above setup without the water drop kit to photograph this type of subject and know what to expect regarding exposure)

Problem
I'm trying to start doing water drop photography but can't begin photographing the drop itself until I first learn how to control the exposure. I can control the exposure just fine with the water drop kit disconnected and using the Commander mode to fire the flash unit. However, when I connect the water drop kit, stop using the Commander mode and input the settings on the flash unit itself, I can't get anywhere near an acceptable exposure.

The settings and results for both situations are explained below.

Settings using Commander Mode (water drop kit disconnected) -- IDEAL EXPOSURE
1 flash unit: Manual mode at 1/128 power
Camera: Manual exposure at flash sync shutter speed 1/250 second, f/36, ISO 100

Settings with Water Drop Kit Connected (Commander Mode not used) -- UNUSABLE UNDEREXPOSURE
NOTE 1: The kit's controller is connected to the camera using one cable and to the flash unit using another cable. The kit's controller releases the shutter and flash timed according to controller's settings (see below). However, the exposure settings pertaining to the flash and camera are controlled by those two devices, not the kit's controller.

1 flash unit: Manual mode at full power
Camera: Manual exposure at 1 second, f/3.8 (largest aperture available), ISO 800
Water drop kit's controller: shutter lag 200ms*, flash delay 400ms**

*Shutter lag is the delay between when the camera is triggered and when the shutter is actually fully open.
**Flash delay is the time delay between when the system starts and the flash output is triggered. The system is started by an infrared remote that triggers the water drop kit's controller.
NOTE 2: The camera is tripped when the timing reaches the Flash Delay minus the Shutter Lag.

Conclusion
I have absolutely no idea why I'm getting such underexposed images when the water drop kit is connected, but I would be willing to bet that it's caused by operator error.

Your help is greatly appreciated!
 
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Joined
Oct 9, 2005
Messages
29,103
Location
Moscow, Idaho
Good thing I just returned home with a case of wine!
This is probably way off target. With my remote setup for my SB-800s (granted it's a wireless radiofreq system) the flash has to be on TTL. If I need to shoot manual flash the changes are made on the camera-mounted transmitter.
 
Joined
Sep 13, 2007
Messages
19,758
Location
Northern VA suburb of Washington, DC
Good thing I just returned home with a case of wine!

YES!

This is probably way off target. With my remote setup for my SB-800s (granted it's a wireless radiofreq system) the flash has to be on TTL. If I need to shoot manual flash the changes are made on the camera-mounted transmitter.

You're correct that the difference is that you're using a wireless radio system. I'm using a wired system that allows the water drop kit's controller rather than the camera to determine when the flash is fired. So, the flash settings have to be made on the flash.

I've not been using the camera's Commander mode to set the flash unit's exposure setting thinking that I wouldn't know whether the camera or the water drop kit's controller is firing the flash. I'll try using Commander mode and the water drop kit's controller and get back to you.
 
Joined
Sep 13, 2007
Messages
19,758
Location
Northern VA suburb of Washington, DC
I've not been using the camera's Commander mode to set the flash unit's exposure setting thinking that I wouldn't know whether the camera or the water drop kit's controller is firing the flash. I'll try using Commander mode and the water drop kit's controller and get back to you.

I'll be darned! I got both the correct exposure and the exposure I would have expected using the Commander mode and the water drop kit's controller.

I sure do hope the kit's controller (rather than the camera) is firing the flash. That's an absolute necessity once I begin making photos of water drops. I'm going to visit the kit's forum about that.

I still don't understand why using the same exposure settings when using the Commander mode or setting them on the flash unit without using the Commander mode produces such drastically different results. Can anyone explain?
 
Joined
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Messages
19,758
Location
Northern VA suburb of Washington, DC
I've got another question about the stuff displayed immediately below:

Water drop kit's controller: shutter lag 200ms*, flash delay 400ms**

*Shutter lag is the delay between when the camera is triggered and when the shutter is actually fully open.
**Flash delay is the time delay between when the system starts and the flash output is triggered. The system is started by an infrared remote that triggers the water drop kit's controller.
NOTE 2: The camera is tripped when the timing reaches the Flash Delay minus the Shutter Lag.

All of that indicates to me that the flash is fired 200ms after the shutter is fully open (flash delay 400ms - shutter lag 200ms = 200ms). When the shutter is set to 1/8 second, which is only about 130ms, my thinking is that the flash is fired about 70ms after the shutter has closed (200ms - 130ms = 70ms). Yet I'm getting a great exposure. Can anyone explain which part of my thinking is wrong? Please keep it to lay terms; otherwise, I won't understand.
 
Joined
Sep 13, 2007
Messages
19,758
Location
Northern VA suburb of Washington, DC
I'm skeptical that the water drop kit's controller is firing the flash; I'd be willing to bet the Commander mode is firing it, which is really problematic if I understand everything properly. I'll test it tomorrow using water drops, as that's the only way to determine whether the timing of the flash is be affected by the controller.

That problem would be solved if I could get a proper exposure by configuring the flash output directly on the master flash unit but I can't make that happen. I have no idea why using the exact same settings in the Commander mode produces an ideal exposure when configuring directly on the master flash doesn't. If someone could solve that problem for that would be fabulous!
 
Joined
Sep 13, 2007
Messages
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Northern VA suburb of Washington, DC
Two helpful insights have now come my way.

The first one comes from someone who has used the water drop kit for six years. She tells me that she uses only the cable that connects the camera and the controller. Perhaps also using the cable that connects the flash unit and the controller was messing up my exposures unless I sort of bypassed it by using the Commander mode. So, I'll try omitting that cable once I start trying to capture the water drops.

I also realized after thorough testing that one of my SB-800 flash units is defective. It took a couple hours to narrow everything down to that but I'm absolutely certain of it. Knowing that also explains a lot of the unexpected exposures I was getting.

The one bit of super good news is that the water drop kit has been dispensing water seemingly properly for three days. That's exactly three times as long as the two previous kits made by a different company. :D
 
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Joined
Jan 22, 2019
Messages
2,503
Location
Jupiter, FL
Real Name
Andy
I have no experience with using timing devices such as your water drop controller, but can say that the Nikon Commander mode seems to be designed to work only with Nikon gear. If the water drop controller has either a hotshoe or sync cord output, perhaps you'd get better results with a separate flash transmitter.
 
Joined
Sep 13, 2007
Messages
19,758
Location
Northern VA suburb of Washington, DC
If the water drop controller has either a hotshoe or sync cord output, perhaps you'd get better results with a separate flash transmitter.

It has a sync cord. The problem when I used it rather than Commander mode, the exposures were hugely underexposed. I think that was true aside from the fact that one of the SB-800s is defective, but I'll double check again tomorrow.
 
Joined
Sep 13, 2007
Messages
19,758
Location
Northern VA suburb of Washington, DC
It has a sync cord. The problem when I used it rather than Commander mode, the exposures were hugely underexposed. I think that was true aside from the fact that one of the SB-800s is defective, but I'll double check again tomorrow.

Now that I've had such an informative chat with you, I'm not going to even bother checking. For now, I'll try using the one SB-800, Commander mode, and connecting only the camera to the water drop kit's controller. Your hunch that both the shutter release and the firing of the flash are transmitted through that cable is consistent with a Canon user's setup she explained to me. Once I receive your Yongnuo gear, I'll incrementally add on to that setup. At least that's the plan. :)
 
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