In order to achieve the best possible flash photography results, taking flash off the camera and using multiple flash units become necessary. For example a typical setup for studio portrait shooting may include key light, fill light, background light, and often hair light. Not all shooting situations require this many lights but it is safe to say triggering multiple lights and synchronizing the light output with the camera’s shutter is the solution the photographer need to find.

Typically corded connections between the camera and flashes are supported by most camera/flash systems but most photographers do not like the hassle of wires. The simplest form of wireless trigger is the inexpensive optical slave triggers. But very often they suffer from poor range and are prone to interference. One step up is radio frequency (RF) wireless flash triggers. These triggers can trigger the flash from long distance and do no require line-of-sight between the transmitter and receiver. Most of the low cost triggers (for example, check out our review of an eBay trigger iShoot PT-04 CN) do not support remote flash power adjustment. All the remote flashes need to be in manual mode. If the photographer needs to change the flash power, he/she needs to get to the flash and change it by using the controls on the flash. Sometimes this is an acceptable inconvenience but sometimes it is unacceptable because of the physical location of the remote flashes or the time required to do so.

This discussion will be focused on wireless triggering and remote power control options currently on the market.

Wireless optical systems

The top two camera manufacturers Canon and Nikon have already the capability in their optically triggered wireless flash lighting system. We have covered extensively how the Nikon Creative Lighting System (CLS) Advanced Wireless Lighting (AWL) actually works. Basically the camera controls a wireless commander unit, which controls remote flash units via optical pulse communication. Canon’s offering E-TTL II Wireless Multiple Flash technology is similar but differ in the implementation details.

The common complaint is the limitation caused by the line-of-sight requirement. This is especially a problem outdoors when there is no walls and ceilings to bounce the lights around. When used indoors, the lights from commander unit can be bounced around and reach the sensor of remote unit without requiring line-of-sight.

To overcome the limitation, some manufacturers have come up with RF-based solutions. The most popular ones are RadioPopper PX and Pocket Wizard MiniTT1/FlexTT5. Pixel, a company based in Hongkong China has also produced products (TR-331/TR-332) that can remotely trigger flash and set flash levels via TTL system.


The RadioPopper PX system is a simple and quite elegant solution. RadioPopper PX transmitter has a sensor that can detect the pulses from master flash unit or remote commander on your camera’s hot shoe. The transmitter sends this signal by radio waves to RadioPopper PX receivers. The receiver then uses it’s own built-in light source (most likely an infrared LED) to reproduce this light signal at the sensor window of the flash. The slave flash responds to the “reproduced” light signal just as it normally would had it seen the light directly from the master flash.

Since all the system does is to transport the optical signal over RF, all the functions of the camera-flash optical lighting system is preserved without even worrying about the underlying details of the communication.

One potential problem of the system is the delay caused by the optical->digital->RF->optical signal conversion and transmission. Some light pulses, such as the pre-flash and final triggering flash, have strict timing requirement to ensure proper metering and synchronization. The RadioPopper system claims to have specific design feature to overcome this delay issue. The user manual does caution users about potential crossed signals: pulses from both master flash and the pulse reproduced by the receiver unit enter the sensor of the flash at the same time. This can be avoided by properly sealing the sensor window on the flash and placing the remote flash away from the master unit.

The RadioPopper PX system appears very easy to use. Users need only to setup the master flash and the remote flashes like they would without the Radio Poppers. The receiver will block the light from master unit from reaching the sensor and the signals are transmitted via RF and converted back to optical signal via a light source at the back of the receiver unit.

RadioPopper JrX system also provide remote flash power adjustment functionality when used with JrX studio receiver. Currently the system only officially support some studio lights but some users have found a way to make a simple DIY adaotpr (RPcube) so it can be used to control the power output of portable flashes. The most significant difference between PX and JrX system is no TTL capability with the JrX and no high speed sync (HSS) either.

The RadioPopper works on 915MHz ISM band and have a claimed range between 300 to 1750 ft. In real world situations, the range can be much less than the claimed values due various factors. A very detailed review of the RadioPopper JrX system review can be found here.

Pocket Wizard

Pocket Wizard MiniTT1 and FlexTT5 system currently available for Canon system works in TTL mode to control one or more remote flashes. The MiniTT1 can only be used as a transmitter but the FlexTT5 can be used as a transmitter or a receiver.

Unlike the RadioPopper system, the Pocket Wizard MiniTT1 and FlexTT5 system communicates directly with the camera and flash via hot shoe instead of converting the signal from the commander to digital, transmiting it over RF, the converting it back to optical again for the flashes’s infrared sensor.

The Porcket Wizard system has two modes. The basic wireless E-TTL II mode fires all flash at the same power while the ratio wireless E-TTL II mode allows flash power ratio adjustments and independent power settings supported by Canon’s E-TTL II system. For the ratio mode to work, a Canon 580EX flash or ST-E2 Speedlite Transmitter has to be mounted on the transmitter.

Nikon version of the Pocket Wizard system is currently under beta testing.

The Pocket Wizard MiniTT1 and FlexTT5 system works on 340 – 354 MHz band and has a claimed range of 800 ft.

Pixel TR-331/332 Wireless TTL Flash Trigger

This product is from a little known company called Pixel Enterprise Limited based in Hongkong, China. They are the maker of another product we have covered, the Pixel TF-322 TTL adapter.

Basically the Pixel system is a “wireless TTL cord”. A transmitter sits on the camera and relays the communication with a flash on a receiver via 2.4GHz RF. It has the capability of triggering multiple flashes but only one remote unit can be in “Master” mode, which talks to the camera and maintains TTL capabilities. Other remote flashes have to be in the “Slave” mode, which can be triggered but will not perform TTL functions such as pre-flash camera-controlled output powers. Essentially there is no way of independently adjusting the flash powers from the camera.

The TR-331 is for Nikon and TR-332 is for Canon. The Nikon version was released earlier and appears to have been improved to a more usable state. If you want to follow the status of the Pixel TTL triggers, here is a good discussion thread on flickr.

If you are interested in finding out more about the Pixel system, the company’s website is the worst place to visit. It has extremely poor documentation. Some good reiviews can be found herehere, or here.

More to come?

We can expect more products to come in the area since currently available options have something left to be desired. Two major aspects: cost and functionality. They are all quite expensive. For the RadioPopper and Pocket Wizard to control multiple flashes with independent TTL flash outputs, a dedicated commander flash needs to sit on top of the camera, which is a waste. When things get complicated, the margin of error becomes small and they tend to mis-fire often. Especially the Pocket Wizard MiniTT1/FlexTT5 appears to have gotten some bad user reviews on range and reliability.

The ideal solution

I am interesting in seeing a new system with a RF version of the SU-800 (Nikon) or ST-E2 (Canon) sits on top of the camera and RF receivers connects to each remote flash on the hot shoe. This setup should significantly reduce the overall cost and simply the use.

With mode and power controls on the transmitter, there is no longer a need to have a wasted commander unit sits on top of the camera as the RadioPopper or Pocket Wizard system requires. With hot shoe mounting for the receivers, the system also eliminates the clumsy mounting method of the RadioPopper receivers.

This system can be made but a complete reverse engineering of the communication protocols between Camera and Flash is required. Personally I think it is highly possible since there are many i-TTL or E-TTL compatible flashes out in the market. Those flashes have to be able to understand the specific camera/flash communication to work.

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