Jay Connor wrote:
Taking a guess and answering my own question
I would say for A 2/3 x 400 = 266 Ws
and for B 1/3 x 400 = 133 Ws
Yes, the ratio is 2:1 not 3:1. 400 Ws with A alone, 267:133 with A and B. Slightly more power and slightly longer duration with the standard S heads compared to the action A heads.
Since these are for portraits not concerned with flash duration but thanks for pointing that out
The reason I posed the question is b/c I was setting up some clamshell lighting in which I would normally have a 3:1 top:bottom ratio
I tried a couple of test shots at 2:1 and they looked ok
But if I wanted a 3:1 ratio, and I wanted to knock down the brightness of the bottom light (and maintain its distance from the subject) does anyone have any suggestions other than using a neutral density gel on the bottom light
Jay Connor wrote:
The reason I posed the question is b/c I was setting up some clamshell lighting in which I would normally have a 3:1 top:bottom ratio
I tried a couple of test shots at 2:1 and they looked ok
But if I wanted a 3:1 ratio, and I wanted to knock down the brightness of the bottom light (and maintain its distance from the subject) does anyone have any suggestions other than using a neutral density gel on the bottom light
It depends on how are you define a 3:1 ratio. Using the old portrait lighting ratios system, fill at half the power of key would have been classed as 3:1 – logically and mathematically incorrect though it may have been.
If you are trying to replicate something that claims to be 3:1, and it is working out, then this may be why.
It wouldn't be that simple anyway to get the ratio you want. Especially if you are not using the same light modifiers top and bottom and the exact same distances. You really need a light meter if it's that important to you.
Jay Connor wrote:
But if I wanted a 3:1 ratio, and I wanted to knock down the brightness of the bottom light (and maintain its distance from the subject) does anyone have any suggestions other than using a neutral density gel on the bottom light
I can't think of any scenario where I would want to have my lighting ratios fixed in this way with any pack system. Each channel should be capable of being set to whatever was needed and not fixed in any specific ratio.
One solution would be to buy another pack.. which sort of defeats the idea of having a two head kit. Having to use ND filters is perhaps the only solution immediately available.
Jay Connor wrote:
...if I wanted a 3:1 ratio, and I wanted to knock down the brightness of the bottom light (and maintain its distance from the subject) does anyone have any suggestions other than using a neutral density gel on the bottom light...
The Jule rating indicates the amount of power going into the flash tube (more-or-less), but it doesn't indicate the amount of light falling on your subject.
As others have said, it depends on what modifiers, reflectors, etc. are mounted. If your top light is in a high-output beauty dish and your bottom light is in a double-diffused soft box the ratio on the subject will be very different than if both lights were in standard reflectors.
You can eyeball test shots to get the look you want, but as was also said, if you want precise ratios a flash meter will be essential.
I did the same thing with a Profoto Acute pack and two lights. Beauty dish up top and small soft box below. I do not remember the ratio now but I remember needing the light a stop less on the bottom than I could get. I just clamped a collapsible one stop diffuser on the soft box with two 99 cent A clamps.
