48" octabox enough for family portrait of 10 people?

I'm doing this for free for my friends except they decided why not throw in a second family

Setup: At the beach, sunset behind them, 5 adults, 5 children. Is my 48" octabox with AB800 be enough? I was thinking of using my Yongnuo YN560II shooting from the back as a rim light.

And where would you place the 48" octabox? 45° right of the camera?

I'm kind of freaking out as I've never done a group shot with two families...and thinking if the light will be soft but enough to cover 10 people.

First, lots of topics on lighting groups here - I would do a search. I also think someone posted a question almost identical to yours in the last 6 months (though I couldn't find it right away). It was a long and interesting discussion on using sunset as background and properly lighting group.

With the sun to their back, I would not think you'd need the flash to provide rim light?

To your main question - it depends. My concern with the Octa (and I've never used one) would be the way it wraps the light. It may not spread enough to cover up close, but when backed up, may lose coverage of the group and/or create harsher shadows than you want. IMHO you need either 2 sources of light up front or a larger softbox.

I would stack the families - 5 adults in back, 5 kids in front. That way, you aren't trying to light as many people across. You'll have to stop down (probably f8 or higher) to get enough depth of field to ensure everyone is in focus.

The problem you will have using a single box is falloff from the center to the edges. It will probably be almost a full stop brighter in the center than the edges of the photo if you back up wide enough to cover a group of that size. Not something you cant handle in post, but it would be easier if you could use two lights.

Ya right before the sunset I don't think I'll need the lighting in the back and maybe little fill flash but perhaps using both units at the front? I haven't done that honestly. And I did notice a slight fall off in light even with two people holding their two children just recently.

Maybe I'll play it safe and get the 10 people shot early with enough sunlight and play around with single family portrait after the sun is under the horizon?

Sunset provides all the backlighting you need. Bring both around to the front and you'll be fine.

Will try it out! Thanks for all the suggestions! I'll use the search function more from now on

AB800 in the octa, with a disk in front of the flash tube ala beauty dish. I'd even leave the diffusion fabric off. Up above the camera about 4 feet, off axis about 15 to 20* get your exposure for ambient minus about 1/2 EV to make sure the sky looks good, then adjust the AB to taste. It will have to be about 10 to 12 feet away from the group. Relatively long lens to keep the front and back heads about the same size. Enough DoF to make sure faces are sharp.

Here is one done with a single Einstein in a medium PLM as shoot through.

BTW, I put the camera on a tripod for these so I can replace a face if necessary.

^ The overall exposure looks a bit under on my monitor, and the faces in the back and sides look considerably under, IMO.

Dave Jr wrote in post #16388304
^ The overall exposure looks a bit under on my monitor, and the faces in the back and sides look considerably under, IMO.

+1.

dmward wrote in post #16387865
AB800 in the octa, with a disk in front of the flash tube ala beauty dish. I'd even leave the diffusion fabric off. Up above the camera about 4 feet, off axis about 15 to 20* get your exposure for ambient minus about 1/2 EV to make sure the sky looks good, then adjust the AB to taste. It will have to be about 10 to 12 feet away from the group. Relatively long lens to keep the front and back heads about the same size. Enough DoF to make sure faces are sharp.

Lots of technical details for an underexposed photo.

The guy in the upper right looks almost two stops under the kid in the foreground, and the kid in the foreground is still a 1/3 to 1/2 stop underexposed.

Keep it simple. Octa right on top of the camera. Can't be that hard. Adequate distance from the subjects will reduce falloff from back/forth and sideways.

Gosh this is a tough crowd! Folks, quit giving Dave flack and obsessing about a shortcoming which is easily due to postprocessing, when the illumination in the photo is just fine!

And Inverse Square falloff of light intensity due to distance is a normal characteristic; even large softboxes falloff according to Inverse Linear!

The size of a softbox does NOT inherently limit its angle of coverage to the degree that folks seem to think!
Here is a shot just taken entirely by flash illumination (ambient light is underexposed by -9EV) using a 5" by 7" softbox, an area about 18 feet wide from distance of 16' with 20mm lens on APS-C.

Wilt wrote in post #16388560
Here is a shot just taken entirely by flash illumination (ambient light is underexposed by -9EV) using a 5" by 7" softbox

Lovely harsh light and well-defined shadows.

Wilt wrote in post #16388560
Gosh this is a tough crowd! Folks, quit giving Dave flack and obsessing about a shortcoming which is easily due to postprocessing, when the illumination in the photo is just fine!

Didn't say that his problem wasn't fixable (or created) in post.

Excessive attention to detail should also continue when you're using the exposure and vignetting sliders.

If he's using a longer focal length lens like he suggested, and has the softbox near the camera position, then it's not an inverse square issue. Distance from softbox to center vs edge subject position is going to be very similar and certainly not 2 stops worth of difference (which would require doubling of distance).

Of course, the key issue here is the one of photo tutorial pontification vs. the need to follow that up with a properly exposed example photo.

So...is there a way to somewhat equalize the light output if the flash is on both sides of the crowd between Yongnuo & the AB800 at least without guessing? Or I just have to play around with different power for one side to match the other?