What zoom settings when using modifiers?

when using my flash off camera bare and on camera it's pretty easy to know what zoom settings to use.

What I can't comprehend is what zoom to use when using it through a modifier such as an umbrella or softbox.

For the meantime I was just using it at 50mm through an umbrella as a main light 3-5ft from subject.

I just got a 20x28" softbox today and was wondering what would be best for it, I'm guessing a wide setting?


My unit has 18-105mm range, thanks!

The idea is to have your speedlite spread its flash as much as possible, so you don't want to zoom, rather you want it set to wide angle (24mm).

Thank you!

I don't know if it helps or not, but when I'm using a diffuser such as an umbrella or softbox, I also deploy the little plastic diffuser built into the flash head. I think/hope it scatters some of the light before it even gets to the umbrella/softbox.

Kevan wrote in post #15921915
The idea is to have your speedlite spread its flash as much as possible, so you don't want to zoom, rather you want it set to wide angle (24mm).

^
You FILL the umbrella or front panel of a softbox, and that determines the 'softness' of the apparent light source...the umbrella itself or the softbox.
Yet you also do not want to waste light by overfilling the umbrella.

Also, pulling the diffuser out, brings the zoom back even further, at least on canon flashes.

Thanks everyone!
I'm using a YN560 II, it technically only does 24mm but the diffuser says it covers 18mm when pulled out.