noobie to "advanced" lighting trying to get a concept

I am sorry to bother y'all on something simple, but after looking at the stickies and some online lighting sites...I still haven't wrapped my head around something

I am an amateur
and I have used off camera lighting in a limited fashion.
I am now interested in trying some "advanced" lighting options
but....

if I were to use a softbox - say a square one - approx 90X90 cm
how much light do I need to have behind the fabric?
If I was speaking about a speedlight (eg 600 ex rt) - would 1 be enough? 2? 3? (i have only seen brackets to hold three speedlights on a single bracket)

Is there a formula out there for a rule of thumb?

if speedlights arent the right tool, how much power of a studio flash head is too little or too much in the same setting?

most likely these questions are very elementary and I apologize for such.

just to explain - I have a project that I want to run with my daughter.
I would like to try some various glamor like lighting scenes
and I wanted to figure out what hardware I would even need (hence budget)

many thanks for any direction on these simplistic queries.

The reason that you don't see brackets to hold more than 3 speed lights is: going from 1 to 2 speed lights adds 1 stop of power. To add another stop, you need 2 more speed lights. To add another stop from there you need 4 (FOUR) more speed lights. Diminishing returns after the first couple lights are added.

Where speed lights fall behind is their ability to "fill" a modifier. Often you'll get a hotspot in the centre, with quite a lot of falloff towards the edges of the modifier. Speed lights are good at throwing light in a certain direction, not very good when it comes to spreading it out. You may get what you need out of speed lights, if you've already got them, give them a go and see. If you decide to get strobes, 200w lights are enough power generally for studio work, you can always up your ISO if you need to. If you want to work outdoors at all, more power is better. I use 600w strobes and it's JUST enough to put a dent in mid-day sun.

thanks a lot for the practical and simple info.

600 w units take me into budget considerations that I was not planning for. I may have to do some creative reconsideration. At least in my neighborhood, 600 w units run about equivalent $1-1.5K each and that is without a trigger mechanism and without the modifier.

Maybe I can see about rental options (if such even exist)

thanks again

ceriltheblade wrote in post #17628746
Is there a formula out there for a rule of thumb?

simon did a great job with giving you a starting point to understanding what you are facing when using speedlights. Everyone has a slightly different opinion but what he has laid down is hard to argue against.

so much depends on what you are wanting and willing to do.

Are you okay with cranking up the ISO?
Is a wide aperture what you want?
Are you shooting inside where you can control the ambient?
are you willing to accept the longer recycle times with 1/1 power on a speedlight?
do you really need the softbox to be filled with light … even from corner to corner?

a 90x90 box is the biggest i would want to stick a single speedlight in to achieve mostly even lighting, At this size you will likely want the box pretty close to the subject and this can be difficult without a good stand and probably a small boom or c-stand and grip arm.

for a glamor shot you will also want at least a hair light, possibly two as rim/hair combo. What about the background? does it need a light?

Once you answer all these questions, the gear list grows and i think it gets to the point where you buy a moonlight or some kind of more powerful light for the main, and then if budget doesn't permit buying more strobes, use the speedlights as rim/hair/background.

ceriltheblade wrote in post #17628768
thanks a lot for the practical and simple info.

600 w units take me into budget considerations that I was not planning for. I may have to do some creative reconsideration. At least in my neighborhood, 600 w units run about equivalent $1-1.5K each and that is without a trigger mechanism and without the modifier.

Maybe I can see about rental options (if such even exist)

thanks again

are you planning to be outside for this shot?

thanks all for the wonderful advice.

the project with my daughter is in the planning phases and inassuch is quite versatile.
There was indeed a plan to be outside, though not exclusively.
part of the decision about the photo locations would indeed be dependent on the ability of the lighting.

I was planning on getting a set of reflectors. That seems necessary.

I wanted to mix up the lighting a bit
including different setups
one of which being a lead light above the camera and a beauty dish under the camera with hair/rim light on the side.
I imagined to myself both lighting at a beach (overpowering a setting sun)
as well as open fields, closed (or mostly closed) wall/buildings

at first I was thinking about a set of parabolic umbrellas (silver and white options), but the octabox and softbox caught my attention a bit more. I was just trying to think what could power them. The more I read on-line, it seems that the authors assumed that you already understood the power behind the scenes - hence the question.

I am open to all critiques, and please understand that while I have been reading for a couple weeks already, I know I have a lot more reading and planning.

I also accept that it is a learning exercise (one that I hope sincerely that has excellent results), and my daughter is very patient. I think I will need that!!!

Big strobes don't have to be expensive. I paid around $300/unit for cheap Mettle 600w strobes. I use YN622's to trigger them ($45 each?). Outdoors, one light is usually all I use. Put the sun behind your subject and it will provide the rim or hair light, use a single strobe as main and reflector as fill.