Bookmark and Share

Slave to the Light

Guide to Battery-free Optical Flash Triggers
by Gisle Hannemyr
Published: 2011-04-20.

This article discusses plain, battery-free flash triggers. To be more precise, it is a survey of triggers of the type that is powered by the flash' trigger voltage and do not take pre-flash into account. These are the simplest devices you can use for firing off multiple flashes. There are no batteries to worry about, and no settings to fiddle with. They are also very cheap (usually around US$ 10). If you can use these, they are great for “strobist” type shooting.

If you also are interested in radio triggers, then please see this article.

From left: FotoDiox, Seagull SYK-4, Wein Peanut, Sonia rotating hot-shoe, Sonia multi-terminal HR.

1. Introduction

Unlike the elaborate light based remote triggering that is provided by Nikon's and Canon's dedicated flash control systems, these simple optical flash triggers mix fine with non-dedicated radio flash triggers. You can use radio to send the signal to lead flashes behind walls or objects, and then trigger other flashes from these with this type of optical slaves. In short, they belong in the kit of every strobist.

Some flashes have a built-in optical trigger (e.g. Nikon SB-910 and most monolights) that will trigger the flash when it “sees” another flash fire. Many flashes do not.

However, some flashes can be turned into a slave flash by connecting it to an optical flash trigger. (See this article for the exceptions I am aware off.)

The range tests was conducted with moderm flash units with ordinary positive trigger voltages. A Nikon SB-600 (2.7 volt) and a Nikon SB-28 (3.5 volt) was used for the range tests. I also own an old Vivitar 283 (113 volt). This was used used to verify that all units also worked fine with a high voltage this high.

2. Pre-flash blues

The flash systems that is part of modern camera systems uses something called TTL metering to control the power-ratio of dedicated flash units. An important part of TTL metering is the use of pre-flash. It works like this: The camera fires one or more low power pre-flashes milliseconds before the shutter opens. It then measures the light from this pre-flash as it is reflected from the subject through the lens (TTL). The camera uses this reading to compute the power ratio for the flash for correct exposure. The camera communicates the desired power-ratio to the flash and the flash adjust its power accordingly. Finally, the camera opens the shutter and fires the flash to make the exposure. This system provides a fully automatic exposure control that seamlessly integrates camera and flash.

Unfortunately, the pre-flash sequence also trigger “dumb” optical slaves so that the flash units controlled by this type of slave trigger will fire before the shutter opens. In other words, TTL metering and “dumb” optical slaves don't mix.

To solve this problem, several manufacturers of slave triggers introduced so-called “digital” slaves. These are programmed to ignore exactly one (1) pre-flash, and then fire as soon as they “see” another flash. The list below is those manufactured by Wein that have this feature.

  • Wein HS-XL D Hot Shoe Ultra Slave
  • Wein PN-XL D Peanut Ultra Slave
  • Wein L8 D Micro Slave
  • Wein XL8 D Micro Ultra Slave

Some point-and-shoot compact cameras emit just a single pre-flash, and the “digital” slaves work well when the lead flash is from such a camera, but it is a lottery whether these will work with a DSLR.

However, the more complex TTL flash control systems that is used in most DSLRs and advanced compacts may emit multiple pre-flashes. These “digital” slaves do not work in such system.

At one point, Wein introduced some models they called “digital smart” slaves. These were designed to ignore multiple pre-flashes. However, these models are no longer manufactured, probably because they were only moderately successful in figuring out how many pre-flashes they should ignore. Some stock remains, and if you are interested you should look for Wein model numbers “W930010D” and “W930015D”. However, to be frank, they were never very reliable, so I do not recommend them.

In my opinion, neither “digital”, nor “digital smart”, optical slave triggers are worth using if you want to use off-camera flash with a DSLR, so I will not say more about them in this review.

Instead, if you want to use optical slaves, get the “dumb” kind and just make sure your lead flash does not emit any pre-flashes. This is usually simple enough, just set it to manual instead of TTL.

3. Connections

There exist a several different connectors for passing the electrical signals from the optical trigger to the flash. The most common ones are:

  • ISO standard two contact hot-shoe.
  • 1/8" male or female pc-sync.
  • Vivitar plug.
  • Household prong.
  • 3.5 mm or 1/4" monoplug.

What type of connection you should make sure your trigger has depends on what type of unit you plan to use it with. Portable battery powered flash units, like Nikon Speedlights and Canon Speedlites, have hot-shoes. Some of these also have 1/8" pc-sync connectors. The popular Vivitar 283 and 285 battery powered flash units have both a hot-shoe and a socket for a Vivitar plug. Mains powered studio flashes have sockets for a household prong or a mono-plug.

4. The models

Fotodiox optical slave trigger.
Fotodiox Hot Shoe Slave Trigger

Fotodiox Hot Shoe Slave Trigger

The Fotodiox Hot Shoe Slave Trigger has a standard ISO two contact hot-shoe and a plastic cold foot with a metal 1/4 inch thread tripod socket. The cold foot is very loose fitting in the Nikon AS-19 flash stand, but fits fine in any lighting stand cold shoe with a locking screw.

The trigger also has a female pc-sync socket on its rear side.

It does not work with modern Canon Speedlites, Sony flashes, nor the Olympus FL-40 Flash.

I measured a range of about 11 meters when triggered by the pop-up flash of a D700 firing a full power. The range was roughly the same for both the SB-600 and SB-28.

Manufacturer: Fotodiox, USA.

Seagull SYK-4 optical slave trigger.

Seagull SYK-3, SYK-4, SYK-5 and SYK-6

Seagull produces a series of slave triggers that all come in a cubic plastic mount.

It has a plastic foot with a metal 1/4 inch tripod socket. The foot also fits a flash stand such as the Nikon AS-19, but is very loose. There is no locking lever or collar. On top there is a standard ISO two contact hot-shoe. In front of the centre contact there is a hole that fits the locking pin on Nikon Speedlights. In the front there is a lens-like plastic “eye” that directs light to the trigger sensor.

The most basic model is the SYK-3. It has no extra sockets or controls.

The SYK-4 has a female pc-sync socket on its right side, but is otherwise identical to SYK-3.

Neither the SYK-3 nor the SYK-4 is compatible with most Canon flashes. They also fail to trigger a Nikon Speedlight SB-600.

The SYK-5 is designed to work with Canon EX-series flashes. Unlike the SYK-3 and SYK-4, the trigger circuit connected to the hot-shoe is compatible with Canon EX-series Speedlites. Like the SYK-4, it has a female pc-sync socket on its right side. On its rear side, the SYK-5 has a switch to toggle between standard flash mode and Canon red-eye elimination mode, and a pot-meter to set a variable delay. Users report that these controls work as intended with Canon compact cameras, but not if the lead flash is the built-in flash on a Canon DSLR in E-TTL II mode. For DSLR use, you need to set the toggle on the back to standard flash mode, turn off the delay, and use a lead flash that does not emit pre-flash. Since it is designed specifically for Canon EX-series flashes, the trigger circuit in the SYK-5 must be different from the other SYK-series triggers. Reader András Iklódy-Szabó reports that the SYK-5 model does not work well with legacy flash units.

The SYK-6 has the proprietary Sony/Minolta hot-shoe in top. Otherwise, it is identical to the SYK-3.

The Seagull SYK-3 trigger is sold by a number of vendors under a number of different names. I have not seen the very similar Seagull SYK-4, SYK-5 and SYK-6 triggers re-branded.

I measured a range of roughly 10 meters for both the SYK-3 and the SYK-4 when used to trigger a Speedlight SB-28 when triggered by the pop-up flash of a D700 firing a full power. It did not trigger my SB-600 at any distance. See comment by Gary below for a possible cure.

According to vendor CowboyStudio, none of the SYK-units should be used with flashes with trigger voltages above 12 volt. Here is the message:

None of our equipment is rated by the manufacturer to handle trigger voltages higher than 12V. If someone one managed to get a similar item of equipment working with a higher voltage it could possibly happen again. However, using them in this manner voids the warranty, as they are only rated for 12V.

Manufacturer: Seagull, China.
Sold as: Seagull SYK-3, Hama 6967, Kaiser K1501.
Sold as: Seagull SYK-4.
Sold as: Seagull SYK-5.
Sold as: Seagull SYK-6.

Plain optical slave trigger.
Sonia Slave with rotating hot-shoe

Sonia Slave with rotating hot-shoe

The Sonia Slave with rotating hot-shoe has a plastic foot with a metal 1/4 inch tripod socket. The foot also fits a flash stand such as the Nikon AS-19, but is very loose. There is no locking lever or collar.

The unit has a standard ISO two contact hot-shoe on top and two female pc-sync sockets. The hot-shoe has no room for the pin-lock you'll find on the SB-600 and other Nikon Speedlights, but my SB-600 fits reasonable tight into the hot-shoe and is held in place by friction.

As indicated by the name, the hot-shoe rotates around an axis. This design seems a weak point mechanically. It makes the whole assembly sag when the flash is not standing upright above it. Since most flash heads rotate anyway, the rotating hot-shoe is not really required. I've made mine more stable by gluing it in place.

The two female pc-sync sockets can be used if you want to trigger additional external flashes from the slave with a pc-male-to-pc-male sync cord, such as the Nikon SC-15 Coiled Sync Cord.

I measured a range of about 10 meters when triggered by the pop-up flash of a D700 firing a full power. The range was roughly the same for both the SB-600 and SB-28.

It does not work with most modern Canon Speedlites.

Manufacturer: Sonia, India.

Sonia HR.
Sonia Slave multi-terminal HR

Sonia Slave multi-terminal HR

The Sonia Slave multi-terminal HR is actually a two-piece unit consisting of a Sonia peanut slave unit and a so-called slave attach hot shoe. Both are also available separately.

The Sonia system is modular, and the slave unit may be of the regular type (yellow base) with a working range up to 12 meters (40 feet), the high range type (orange base) with a working range up to 18 meters (60 feet), or Canon EX compatible type (green base).

The Sonia modular peanut slave units also comes with different connectors, including Vivitar plug, mini-phone, pc-sync male and pc-sync female. The slave attach hot shoe also comes with different connectors.

This means that you can buy a Sonia peanut slave unit that plugs directly into a Vivitar 283, or one that can be plugged into a slave attach hot shoe. However, user colinsfoto (who sells these units) has reported that the the Sonia peanut slave unit should not be used with flashes with a trigger voltage above 100 volt.

The slave attach hot shoe has a molded metal body with a 1/4 inch tripod socket in the base. The base also fits a flash stand such as the Nikon AS-19, but is very loose. There is no locking lever or collar. It has a single male or female pc-sync connector (for connecting the slave unit), two female pc-connectors (for connecting up to two flashes using pc-male-to-pc-male sync cords), and a standard ISO two contact hot-shoe on top (for mounting flash).

This arrangement allows up to three flashes can be connected to the multi-terminal and triggered by a single Sonia peanut slave unit. The three flashes may may have different trigger voltages. The slave attach hot shoe is designed to prevent any current flowing between the attached flash units.

Working range depends upon what Sonia peanut slave unit you use. I've only tested the high-range model.

The unit tested by me is a high range model (orange base) with a female pc-sync connector that also allow it to be connected directly to a flash with a female pc-sync connector with a pc-male-to-pc-male cord or this pc-male-to-pc-male adapter.

I measured a range of 16 meters when triggered by the pop-up flash of a D700 firing a full power. The range was roughly the same for both the SB-600 and SB-28.

FlashZebra (US) and Colinsfoto (UK) carries a number of modules compatible with the Sonia system.

Manufacturer: Sonia, India.

Plain optical slave trigger.
Wein PN Peanut

Wein PN and PN-XL Peanut

Wein produces a broad range of optical slave triggers, including some expensive models that are programmed to ignore the pre-flash that most digital cameras use to compute flash power. In this test, I shall only look at the Wein's “dumb” slaves that, like the others in this review, trigger as soon as they see the light of another flash.

The Wein PN Peanut Slaves comes with a hybrid Vivitar/female pc-connector that fits both a male pc connector and a Vivitar connector. Wein makes a special double pc-male-to-pc-male adapter that may be used to conect the PN Peanut (and other lightweight slaves with female pc-connector) to a flash or foot adapter with female pc connector. Instead of the double adapter, the PN Peanut can be connected to a flash with a pc-male-to-pc-male cord, but I would not recommend this, as it sometimes gives a bad connection.

Wein PN Peanut. Wein PN Peanut.
The Wein PN Peanut is the perfect match for the Vivitar 283.

The hybrid connector plugs directly into the proprietary Vivitar connector found on the Vivitar 283 and 285. The photos above show a Wein Peanut PN plugged directly into a Vivitar 283 by means of this connector.

Plain optical slave trigger.
Wein PN-XL Peanut Ultra

The Wein PN Peanut Slave is minute in size and weighs only 15 grams. Its rated range is 30 meters. When triggered by the pop-up flash of a D700 firing a full power. I measured 17 meters when connected to a Nikon Speedlight SB-28 via the pc connector and 20 meters when plugged directly into a Vivitar 283.

Its bigger brother, the Wein PN-XL Peanut Ultra (see photo on the right) is larger in size and weighs 30 grams. Its rated range is 90 meters. However, I could only get it to fire consistently within a range of 10 meters when connected to a Nikon Speedlight SB-28 via the pc connector. When plugged directly into a Vivitar 283 the range was also 10 meters. When triggered by the pop-up flash of a D700 firing at 1/128 power, range was identical (i.e. 10 meters). The range is of course much lower than its rated range. When the lead flash fires at full power its range is even lower than the range of its little brother. I am not sure what to make of this. Maybe the PN-XL unit I had access to for this test was broken?

Because the Wein PN Peanut slave triggers do not have a hot-shoe, they are not suitable for units without any external sync connector, such as the Nikon SB-400, the Nikon SB-600 and most modern Canon Speedlites.

Manufacturer: Wein, USA.

5. Range and high-voltage tests

The table below gives an overview of all the models covered in this review.

The range tests were conducted indoors, in a long corridor with standard fluorecent overhead lighting. All the tests were done in a single session with the optical trigger and flash sitting on a light stand on the same spot. The pop-up flash of a a Nikon D700 (GN 13, meters, ISO 100) was used as lead flash. I first tested the range by firing the lead flash at 1/128 power, and then again at full power (1/1). I paused at least 10 seconds between each shot to make sure both the pop-up flash and the slave flash were full charged. To make sure results were consistent, I made sure that the slave were triggered by at least three shots in a row from the same position.

The distances below are the maximum reliable trigger distance in meters I found for a Nikon SB-600 (trigger voltage of 2.7 volts), and a Nikon SB-28 (trigger voltage of 3.5 volts). A Fluke 411D laser distance meter was used for range measurements.

The column “HV” shows the result of testing with a Vivitar 283 (trigger voltage of 113 volt). This was done in a different setting, so no maximum trigger distance was recorded. An “OK” indicates that the the trigger was able to trigger the flash and didn't fry. A “NO” in this column means that the trigger is said by the manufacturer or a vendor to be unsuitable for use with high voltage units. While such units may trigger with high-voltage flashes when testing, there is no guarantee that long-term exposure to high voltage may not damage the trigger.

None of the units is said to work reliable with flash units with reverse polarity.

Product SB-600 (2.7V) SB-28 (3.5V) HV Source
Fotodiox Hot Shoe Slave Trigger OK eBay
Seagull SYK-3 XX5.110.5 NO Amazon
Seagull SYK-4 XX5.110.5 NO Amazon
Seagull SYK-5 NCNCNCNC NO eBay
Seagull SYK-6 NCNCNCNC NO Amazon
Sonia Slave with rotating hot-shoe 5.710.65.710.6 OK eBay
Sonia Slave multi-terminal HR 7.516.27.616.3 NO eBay
Wein PN Peanut NCNC8.417.3 OK B&H
Wein PN-XL Peanut Ultra NCNC10.510.6 OK Amazon
Table shows maximum measured trigger range in meters indoors using the built-in flash on a Nikon D700 (GN 13, meters, ISO 100) as lead flash. X=Did not trigger. NC=Not compatible. NT=Not tested. NO=Not suitable to trigger high-voltage equipment.

None of the units tested could be triggered at the distance given by the manufacturer as the maximum distance. However, when testing, I found that range was highly dependent upon external factors, such as the ambient light and the power of the lead flash.

When I took testing outside, in bright daylight, ranges were drastically reduced. When I used a Speedlight SB-910 at full power as lead flash, ranges became longer. Hence, the range numbers in this test is only a measure of the relative sensitivity of the units tested. What range you actually get when using this type of trigger will vary with the conditions the trigger unit is used under.

The flash used by me for the high voltage testing has a trigger voltage of 113 volt. This is currently the highest trigger voltage flash I have access to. However, a single test is not a good measure of how good a trigger handles high voltage, as damage may not necessarely lead to instant failure, but may accumulate over time. This type of trigger is, however, cheap enough to experiment with. I would love to hear from anyone that have experimented with higher trigger voltages.

6. Final remarks

If you know about other optical flash triggers that belong in this survey, please use the comment field below to add your experiences.

Bookmark and Share