A company called Pixel, located in Shenzhen, China offers a radio trigger that is compatible (sort off) with Nikon's i-TTL and Canon's E-TTL dedicated flash control systems.
The Pixel Knight system is being advertised by Pixel as an i-TTL or E-TTL II radio trigger. However, the first thing you see when you open the user manual for the Nikon version is the following statement: “Knight TR-331 product will not support the creative CLS system of Nikon wireless flashgun.” Since many Nikon user's think about wireless i-TTL and CLS as more or less the same thing, this statement may puzzle some users. What sort of unit is this?
Well, it is what Pixel says it is: A radio trigger that can be used to wirelessly trigger and control remote units that are compatible with Canon's and Nikon's dedicated i-TTL and E-TTL II systems. It works by “fooling” the remote units hooked up to the Pixel Knight RX units into believing they are in the camera's hot-shoe. In many ways, Pixel Knights works as a wireless off-camera shoe cord. This means that they will, for instance, work fine with i-TTL compatible SpeedLights that do not support Nikon's Advanced Wireless Lighting (AWL) protocol, such as the Nikon SB-400. The Nikon SB-400 cannot be triggered wirelessly by Nikon's SU-800 wireless controller, but can be triggered by the Pixel Knight RX!
Another way of looking at it, is that the Pixel Knight system do the same thing as the PocketWizard ControlTL system in basic wireless TTL-mode. However, unlike the PocketWizard system, the Pixel Knight offers no advanced mode that allows you to control different zones.
The Pixel Knights communicates on the 2.4 GHz frequency (unregulated worldwide), provides 15 selectable channels and 5 groups and works at distances between transmitter (TX) and receiver (RX) up to 65 meters. Each unit uses one CR-2 3 volt lithium batteries. The trigger voltage of a unit connected to the hot-shoe or PC-socket of the Pixel RX should not exceed 36 volts.
Note, however, that the channels and groups are not compatible with the channels and groups used by Canon's E-TTL II wireless control system or Nikon's AWL. There is no way to mix the Pixel Knight system with the manufacturer's own wireless control units (such as Nikon's SU-800 or Canon's ST-E2).
The user manual is in English as written by the Chinese. Some of it is a bit hard to grasp (what is a “vice factory flashgun”?), but most of it is comprehensible.
The Pixel Knight first shipped in December 2009, but the initial units was clearly not ready and very buggy. There are some very negative reviews on the Web from user's that received these early versions. The (so-far) latest version (tested here) was released in February 2010, with reliability is now much better. But they still sometimes “freeze“ and you have to remove the batteries to get them going again. If you want something that is glitch-free, consider RadioPopper PX instead.
According to Pixel, it will work with Canon's EXII generation Speedlites (i.e. 430EXII and 580EXII) and only for certain Canon DSLRs (the manual says 1DII, 1DIIN, 1DsII, 1DIII, 5DII, 7D, 10D, 20D, 30D, 40D, 50D, 350D, 450D, 500D, 550D, 1000D). There is also some limited compatibility with some older Speedlites, such as the 550EX, and Sigma EF-530 DG Super.
The Nikon version is listed as compatible with the following Nikon SpeedLights: SB-900, SB-800, SB-600, and SB-400.
The manual power settings seems to use the legacy quench mode and does not work with the SB-400, SB-700, SB-900 or SB-910. Pixel lists it as compatible with the following Nikon DSLRs: D3-series, D700, D2-series, D300, D200, D90, D80, D70-series, D3000, D5000, D60, D50, D40-series, the Nikon F6 SLR, and the following compacts: Coolpix 8800, Coolpix 8400, Coolpix P5000, Coolpix P5100.
Newer cameras are not listed by Pixel, but this is probably because the manuals were printed in February 2010. I've not seen any reports about the units not working with newer camera models such as the Canon EOS 600D or the Nikon D7000.
I tested a TR-331 TX and RX pair with a Nikon D80 and an SB-800 Speedlight.
I found that the main benefit of the Pixel Knight is the ability to transmit the camera settings that apply to the flash (focal length, ISO, shutter speed, and any settings you can set in the camera's menu to an off-camera flash). Changes made on the camera are sent to the off-camera flash by half-press. To get this to work reliable, you have to pause for at least half a second between half press and full press. Except for the need to pause, signalling works as though the remote units were sitting in the camera hot-shoe. This means that you are able to remotely control functions like manual power settings, FOLC/FEC and FP/HSS from the camera's menu. Only the Nikon version of the unit supports wireless rear curtain sync.
As noted in the introduction, the Pixel Knight works like an off-camera shoe cord. However, unlike an off-camera shoe cord, the Pixel Knight does not let you run the flash connected to the RX unit in Canon's or Nikon's commander mode. This means that you can not use it for hybrid set-up where you control a commander Speedlight or Speedlite by radio, and use this to control several groups of remotes by light.
The simplest setup involves just a single remote flash connected to the hot-shoe of the Pixel Knight RX unit. You mount the TX unit in the camera's hot-shoe, set both to the same channel and group, and you're able to control the remote flash in both i-TTL and manual mode.
It is possible to buy additional RX units and communicate with more than one remote flash unit. The TX has five groups (again: these are not compatible with the groups you'll find on Canon's and Nikon's flash commanders). Each of the five groups can be set to one of the following modes: TTL, Manual or Off. Here is how these settings work:
- One TTL group: If you set one or more groups to TTL, they effectively operate in tandem as a single group. All remote flash units will emit a simultaneous pre-flash. The power level of this group will be determined by the camera's TTL logic. Each remote unit will fire at the same power level. Any FEC/FOLC set on camera will also be applied to all remote units in the TTL group in tandem.
- Up to five independent manual groups: Each group on the Pixel Knight (A to E) set to a manual can be set to operate independently. The power levels on each can be set remotely from the Pixel Knight TX. This only works with units that support Nikon's legacy quench protocol (i.e. the SB-800, SB-600, and older dedicated Nikon Speedlights incompatible with i-TTL).
- Off: You can turn off any group from the Pixel Knight TX. This may be handy when in a complex setup where you have several groups of flash units set up, but do not want to use them all at the same time.
Since only a single remote group can successfully be controlled by TTL, there is no way to use TTL for power ratios. In this respect, the Pixel Knight TX offers less than Nikon's and Canon's wireless commanders, PocketWizard ControlTL and RadioPopper PX.
It is possible to combine the single TTL group with one or more manually controlled groups. But the light contributed by manual groups will not be taken into account when power is computed for the TTL controlled group, so this is mostly useful for manually controlled background light with the TTL group as key.
Also: If you connect a non-compatible flash unit to the hot-shoe of the RX, or anything to its PC connector, the flash unit will fire if the corresponding group on the TX is set to TTL or manual. The power of these units, however, will not be controlled by the Pixel Knight system. In this case, the Pixel Knight operates just like a non-dedicated radio trigger.)