buddhadude wrote:
My flash settings are:
Flash mode: Manual Flash
Shutter Sync:1st curtain
Wireless Func: Trigger off-camera Speedlites only
Channel: 1 Ch
I don't understand what is going on and why it would only work in MULTI mode
The red settings are going to be the root cause of the issue. The Canon (and every other brand) optical wireless function works by sending a "Morse code" of light signals from the master flash to the slaved flashes. This all happens before the actual exposure, and Canon dedicated slave flashes know to wait a set amount of time before they flash so they go off during the actual exposure.
Additionally, any active TTL flash setting will have at least one flash before the exposure to determine what the camera thinks is proper exposure.
The White Lightning (and most other brand) studio flash units have "dumb" slaves that trigger when they see a flash, regardless of its purpose. So if you have a TTL preflash or a wireless command flash that goes off before the exposure, the WL will go off before the exposure, too, as it responds instantly, unaware that it is too early.
If the flash is set to a high-ish power, it will not have enough energy to go off with the exposure flash from the camera (assuming there is one). Sometimes, at lower powers, the light can recycle fast enough to fire again at the right time, but this is not optimal. If there is no flash during the exposure (like how you are set), then the flash will not fire at the right time, regardless of power setting.
Turn the 580 to M mode, and turn the wireless function off entirely. If needed, set it to fire during exposure. You can manually lower the flash power so that it does not affect the final image.