Was asked to do a quick comparison of the light output from my Elinchrom Rotalux Deep Octa 100cm with and without the 40 degree grid that I had custom made from this fellow here: https://sites.google.com/site/gridssoftbox/
Here we are metered at f5.6 SS 1/200 iso 100 with the Deep Octa mounted on a Profoto D1 Air 500w. As you can see, pretty much spills everywhere.
And here it is with the 40 degree grid. I meter at f6.3 with the grid, so you lose a third stop of light with it on so super minimal. Works amazing for when you’re in a small space and want to limit the amount of spill bouncing around the room, reeking havoc on your end exposure.