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Canon EX 600 RT flash and ST-E3 RT control

Field test

I could take Canon EX 600 RT radio controlled flashes and the ST-E3 Rt control unit into my hands thanks to Canon Hungária, and I could also buy one set for myself in the Canon Pro shop of Camera Kft (Canon service). We collected everything just in time, thus we could start the testing with two control units and four flashes. Before I give a report on the field work, let’s see what technological novelties characterize Canon’s cutting-edge radio flashes.


Canon Speedlite EX 600 RT really offers the freedom of flash photography. The new flash is often mentioned as the successor of Speedlite 580EX II, but that’s not completely true. The biggest innovation of the system is that it is Canon’s first wireless radio controlled flash unit. It is recommended to purchase the also new Speedlite ST-E3-RT transmitter which provides further opportunities and great freedom for nature photographers and photographers who want to use creative lighting techniques.
Photo: © Tamás Imre

Canon EO S 5D Mark III, EF 200mm f/2L IS USM 1/200 sec f/10 ISO 800
In fact the point of the flash is that it can perceive the signals of the transmitter (ST-E3) even from distance of 30 metres, which can be freely controlled from the camera, so it is suitable for hide photography and outdoor photography where the parts of the system can perceive each other even in sunshine as they are radio controlled.
The performance has been enhanced up to 60 key number (at ISO 100-200 setting), and the focal-length was expanded for 200 mm lenses as well, so distant subject could be illuminated creatively. If you turn down the diffuser of the flash it can illuminate the angular diameter of even a 14 mm focallength, extra wide-angle lens. The catch-light is very useful, although it is rarely used in nature photography. In this case the tilted flash-head gives a more favourable, nicer light from a reflecting surface (it can be a reflector as well).
This is the first time we receive a new filter adapter for the play of the white balance. It give great freedom as we can use it for the further balance of the flashed subject or the background light or just to the contrary. We have also received two gel filter for the flash as an accessory with which we can play with the colour temperature of the flash. If necessary, use these tools to balance the artificial light of the traditional incandescent or mercury vapour lamp.


Speedlite 600EX-RT and Speedlite ST-E3- RT transmitter was particularly designed for professional nature photographers, with the same robust and weatherproof structure of EOS- 1D X camera. Either placed into the hotshoe or controlled externally coldness, heat or humidity cannot damage the device as the design of the seals make it suitable for photography extreme conditions.
Superb: that’s what they write about every professional equipment and that is true. The average user might not be able to exploit these opportunities but those who like pushing the boundaries can do it as there are places where we can take advantage of these extra facilities. Such places are rain forests which can be characterized by high humidity.

Synchronization of the flash system

The synchronization of Canon EX 600 RT and Speedlite ST-E3-RT control system works as follows. First you have to switch on the ST-E3-RT control unit mounted on the camera which instantly gets into master mode. Here you have to select in the menu through which channel we want to communicate with the flash, then you should set the slave mode on the flash and set the same channel, let’s say channel 2. Once this is done on both devices, look for the led labelled “link” which will be green when the two devices found each other. From this point everything goes quite smoothly, the rest of the flashes should be connected the same way, there can be a, b, c, d, e groups and the performance of each of them can be set individually and at system level as well. These can be Manual, ETTL , ext.A, thus each flash can be controlled separately, according to the requirements. Special features of the system: If there is already someone on the same channel, your controller link led switches to orange indicating that it is already in use. In this case you can add a unique ID, which can be set to 0000 by default, but there are millions of variants. The system is completely customizable with the photographer, so the “cross shootings” with other photographers on the same site are excluded.
Photo: © Tamás Imre

Canon EO S-1D X, EF 200mm f/2L IS USM 1/200 sec f/11 ISO 400

Costa Rica rain forest

I tested Canon EX 600 RT flashes and controls in different extreme conditions, not caring about the rain, mud and high humidity. May it sound a bit rough, but it was my goal to establish such conditions in which flashes has not been used so far. First we photographed colibris in the hidden rain forests of Costa Rica. In that case I used the flashes primarily for illumination with TTL and Manual settings. The radio control worked perfectly even in sunlight and there was no error in the recharge. However, I missed an important setting in the ST-E3-RT controller: unfortunately high speed, that is fast flash sync control is not possible. But the Canon EX 600 RT as master controller mounted on the camera body could control the other flashes without any problems in fast flash synchrone.
The test shots were taken at. 25-30 C° and at 90 % humidity. The second trial was more difficult, we shot fruit-eater bats at night. Well, it was a real challenge, the temperature was about 10 ° C degrees, and full of darkness and torrential rain on us. I used three Canon EX 600 RT flashes, plus the control unit. I set two flashes on the front lights manually, and one for the background, in order to avoid the background to be completely black behind the bats. I was standing under a small shanty, protected from the rain, but the flash units out there in the rainforest, and they were doing their job at high humidity and among flying bats. The point is that these nocturnal animals flew for the nectar which was placed out for the hummingbirds. I had not to walk to the flashes at all to set them, I did everything by the control unit, they communicate with each other for several hours without any error.


Canon extended far forward compared to other producers’ flash systems with this radio controlled technology. All accessories have been added, I did not miss anything. I can recommend it to everyone who can afford it. Unfortunately the system is not compatible with the old Canon EX flashes due to the radio control system.
Tester: Tamás Imre
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