Paul C. Buff, Inc. Technical Forum

I have two Einsteins and am somewhat new to lighting. Am experienced friend indicated he likes to two a 4:1 ratio between the main light and fill light, i.e. F11 and F5.6. Am I correct in saying, using the EU numbers on the Einstein, having a 4:1 ratio is as easy as using EU4 one light and EI1 on the other (or EU7 and EU3 etc)?

If I'm correct, its a whole lot easier to do that with the Einstein.

Thanks.

each increment of the EU (essentially useless) numbers is a doubling of power. So, a difference of 3 (EU 1 and 4, EU 3 and 7) is an 8:1 lighting ratio.

Here's the EU numbers for some common ratios...

• 1:1 0.0
• 1:2 1.0
• 1:3 1.6
• 1:4 2.0
• 1:6 2.6
• 1:8 3.0
• 1:10 3.3

You also have to take into consideration the light modifiers and the distance from the lights to the subject. If both lights have the same size and brand of soft box, and both are the same distance, then you can use the EU numbers directly. Otherwise, you have to either know the EU number compensations for each light modifier and the distance ratios, or...

Use the really amazing CyberCommander to meter and set lighting ratios in seconds, by the bargraph heights. Go to the subject position, meter the main, meter the fill, and then, for 4:1, adjust either the main or fill until the yellow marker (the metered power) for the fill is 2 stops below the yellow marker for the main. The CyberCommander screen has lines in full stop power increments, so the 4:1 means you need to be two line heights different. It will also, when you toggle over to each channel, display the power in log units, so you can do the difference that way. But I find the line heights are so easy...

EU numbers are a different way of stating Ws. EU10 is 6400Ws as a reference point. Yes, 4 whole EU numbers is a 4:1 light ratio, but that also assumes all other variables are equal. Since they are not usually equal, you can use the Commander's meter to do this accurately. Meter your main (lets say it says f16), then meter your fill (lets say it meters at 11.7). You have a .3f difference, but you want a 4f difference. Drop the power of your fill until it says f/4 at the top. Your lights are now in ratio based on actual meter readings regardless of where your lights actually are or how they are modified.

So with that being said, each horizontal line then is 1 stop?

Yes.