(off-camera flash) way to have both radio transmission AND pc cord/old flashes?

Apipes

I have a Canon 5D Mark IV that I currently use with a ST-E3-RT transmitter to work with three 600-EX-RT flashes in three separate groups. Works great. However, there are occasions in which I could benefit from some additional angles of light. Obviously, I could buy additional 600-EX-RT flashes. BUT, I currently have some older flashes I was curious if I could put back into service. I have one 580 EXII and two 430 EX II that I used to use with an ETTL cord prior to upgrading to radio transmission. Would I be able to use a PC cord between camera and the 580 (while simultaneously using my radio transmission/hotshoe with the 600-EX's?). I understand the PC cord doesn't transmit any ETTL info (which I think means I would just need to set the 580 settings on the flash itself). If so, would the 580 be able to act like a master and trigger a 430? If not, then would I be able to use a splitter and have two PC cords to each of my old flashes?
I realize I could buy a PC cord and try - but figured there may be knowledge out there which would help me (and I also didn't know if I could ruin anything by trying without additional knowledge). thanks!!

ziggy53

I'm not aware of any Canon products which do what you want to do. There may be some third-party EOS-HOTSHOE-PC-HOTSHOE adapters available to put between camera and ST-E3-RT master to give you a pc-connector, but I don't know of any I would recommend.

There are some optical slaves designed to mount on manual flashes, and those should work on the 580EX II in manual mode. I don't know if the 430EX II flashes have a manual mode or not, so they might be problematic.

After using cords on cameras for years (40+ years of older large format cameras) I try to avoid cords now.

I have a large number of old 580EX and 550EX flashes which work well as manual flashes.

Apipes

Thanks for your insights! What do you use to trigger your old flashes?

ziggy53

For recent shoots I've mostly moved away from using speedlights/speedlites for primary lights, key and fill lights for instance. I sometimes use them now for background, rim/hair and catch lights. As such, simple master/slave units like old Yongnuo sets work fine for any manual flash. (I think mine are YN 603 (original) series slaves, ancient but still working.)

For large venues, like my church for example, I use a pair of 1800ws monolights aimed backwards and into the pseudo-dome ceiling, along with a single, camera-mounted 580EX for catchlights.

Apipes

Thank you! I don't have any monolights, but can definitely appreciate situations such as you referenced, in which they would be handy! Thanks for all your responses!

ziggy53

Be sure to check out the "Strobist" blog for some great discussions regarding small flash units and off-camera applications.
https://strobist.blogspot.com/

Lighting 101: Introduction