The Most Frequently Asked Questions
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- Can I use the crossed-beam photogate with the Multi-Trigger?
- How do I photograph drop-on-drop collisions?
This is a useful thing to be able to do if you're, say, photographing insects, birds, or other unpredictable subjects. You simply can't hold the shutter open waiting for the subject to do its thing. Our triggers and delay unit will trigger either flash units or camera shutters that have electronic shutter cables. If you're doing this yourself, you'll need to cut your remote shutter cable in order to splice it to the trigger or delay unit output. The remote cables usually have 3 wires. Shorting 2 of them together performs the autofocus and exposure operations of the camera. Shorting the 3rd wire to the other two closes the shutter. You would use the output of the trigger or delay unit to perform the latter function.
Some cameras have shutter cables designed especially for DIY projects. An example is the Nikon MC-22 remote cord which works with the Nikon D series cameras with the exception of certain models (see below). The cable ends of the MC-22 are blue, black, and yellow. Shorting the blue and black ends together does the autofocusing and exposure operations. Shorting the yellow cable to the other two actuates the shutter.
Cameras with infrared remotes such as the D70/70s aren't well-adapted for use with our triggers. While you might be able to wire a trigger directly to the remote, the shutter lag may be unacceptable for high-speed applications. See this link for a discussion.
A sound trigger, photogate, and delay unit cover many situations. The variable-width photogate (SPG1) provides for flexible positioning of the emitter and detector. You can also replace the infrared LED with a red laser pointer in order to operate the photogate over large distances. A delay unit is often used with a photogate. If, for example, you want to photograph splashes, you need to delay the discharge of the flash from when the drop passes through the photogate until it reaches the water's surface.
When using the sound trigger, delays are usually set according to the distance from the source of the sound to the microphone. Figure a delay of about a thousandth of a second per foot (30 cm) of distance. If you need particularly long delays, then it becomes convenient to use a delay unit. You can use the same delay unit as for the photogate.
The delay unit can also be used with a contact trigger. See this page about contact triggers. You would simply connect the two wires from the contact trigger to the input and the ground of the delay unit.
Here's a comment from Scott Thorson: "I spent some time last night working with the flash triggers (sound and photogate) and my Pocket Wizard Plus II’s. I can definitively say that it works. Using the same flash outputs (1 & 2) from the circuits set up for Canon flashes, I can trigger the PW’s. I successfully triggered the PW’s from the “camera/flash” mini plug port (on the top near their antenna) as well as from their hot shoe (using a Paramount mini plug to female hot shoe adapter cable). This worked wonderfully and allows me to trigger several flashes and my camera as well, so I can take shorter exposures and not have to have the room totally dark to get the same effect."
Yes, this is possible with some flash units. One method is to connect the flash units in parallel across the output. We've used this method with as many as 10 Vivitar 283s. This works best if using all the same make/model of flash. It's not recommended if using different flash units, and it's possible that it won't work for some models. And here's something to be especially careful of. There are two different version of Vivitar 283s; the older version has ~300 V across the flash terminals. Connect one of these in parallel with a neter version that has ~10 V and you could have problems.
Another method which gets around the possibilty of one flash's trigger circuit affecting anothers is to use wireless transmitters and receivers, such as PocketWizards. Connect a transmitter to the output of the trigger circuit. Then put receivers on the flashes that you want to discharge simultaneously.
If wireless transmitters are too expensive for your budget, use the output of the trigger circuit to discharge a master flash. Then use optical slaves on the other flash units. This is much less expensive than wireless (radio) devices. If you want to make your own, see this light-activated trigger.
With critical alignment and sensitivity adjustment, 12 inches (30 cm) is possible. For larger distances, a red laser pointer can be used in place of the infrared LED. The detector is sensitive to red light as well as infrared. When using a laser, you may need to place a pinhole aperture in front of the laser so that the beam on the emitter isn't too intense. (This tip comes from Roy Marshall.) Note also that a red spot may appear on the subject so try to arrange things so that the red spot will be on the opposite side of the subject as the camera. Alternatively, you might be able to edit the red spot out of the photograph.
One problem with many laser pointers is that the pushbutton is momentary. If you use such a pointer, you need to clamp or tape the button down. There are sources for inexpensive laser pointers with switches that lock in the on position.
If your flash unit doesn't have a cord, it must have connections on the foot for triggering it. You can get an adapter shoe that fits on the flash foot and has an output PC cord. You should be able to find these in camera stores or purchase one from the HiViz store.
First put the SB-600 in manual mode. Then you'll need a way to attach the SB-600 to the trigger circuit output. See the following link for a way to do that.
Thanks to Tom Denham for the information above.
The variable-width SPG1 is more flexible than the fixed-width SPG2, because the emitter and detector of the SPG1 can be positioned independently of each other. Objects of various sizes can pass through the SPG1 photogate. The SPG2 uses an interrupter as shown to the right. The emitter and detector are fixed in position in a plastic housing. This is convenient for triggering on drops but is limited to objects that can pass through the gate. You can use either type of photogate with the same base trigger circuit.
The SK2 is designed to trigger on loud and sharp sounds such as that of a balloon burst, hand clap, or finger snap. In order to capture water splashes, a photogate with delay is the recommended trigger. The drop passes though the photogate and starts the delay timer. After a preset delay, the delay unit triggers the flash unit or camera.
When connections are made according to this chart, the output is a short circuit. This can be used to trigger most flash units. When connections are made according to this chart, there is a voltage output a little under 9 V. This can be used to actuate an optoisolator (such as the Opto-Switch) or a flash unit that requires a low-voltage trigger pulse.
Cameras should not be connected directly to the low-voltage outputs.
The circuitry for the crossed beam photogate is different from that in the Multi-Trigger. So you couldn't, for example, connect the PVC frame to the photogate input of the Multi-Trigger. You can, however, use the delay unit of the Multi-Trigger with the crossed-beam photogate. To do this, you would connect the SCR output of the crossed-beam photogate circuit to the external input of the Multi-Trigger.