How external Flash works as slave. 420ex & 430ex

[Usaf]

Camera Canon 40D

Speedlites Canon 420ex & 430ex.

how I can use these two speedlites as slave with Canon 40D without Flash a tigger. Do the camera pop-up work as Master flash or is there any other way?

[cicopo]

You can't trigger them with the built in flash unless you add slaves to trigger them. The 420 & 430 EX are triggered remotely by an infrared signal, not just a flash. These can trigger them just because it sees a flash occur.

http://www.bhphotovideo.com/c/product/774432-REG/Dot_Line_DL_0129_Slave_Flash_Unit_with.html

or

http://www.bhphotovideo.com/c/product/858969-REG/Photogenic_913667_PG750_Slave_Trigger.html

http://www.bhphotovideo.com/c/product/764705-REG/Nisha_FSU_Flash_Slave_Unit.html

However they can't control the output as they are just a triggering device.

[Mykolas]

Hi Usaf,

Adding to what was said above, we have our own device that can trigger your Speedlite 420EX and Speedlite 430EX.  It is the Speedlite Transmitter ST-E2.  This mounts to the hotshoe on top of the camera.  When you take a picture, the camera sends a signal to the transmitter, which sends a signal to the flashes to trigger them.

On some of our newer camera bodies that have a built-in flash, the flash on the camera can function as a master.  However, this was a newer function that was not available on the EOS 40D.

If this is a time sensitive-matter, additional support options are available at Contact Us.