Paul C. Buff, Inc. Technical Forum

I have an Einstein along with an SB-900 and I was wondering how I could use light ratios with these two.

Example:

If I am using my Einsten as my primary light at 3/4 power and say an aperature of 8 and I wanted to have my speedlight at half that ratio, how would I set up my SB-900

In manual mode I can configure the power (from 1/1 to 1/125) and I beleive aperature as well, but full power on the SB900 is not the same as full power of the Einstein, so how can I set up ratios if both power sources are different?


Thanks.

You would have to meter and adjust the SB900 until it reads f/5.6. Depending on the distance and modifier used, it could be at any power output. Also, remember that a f/8 light and f/5.6 light on the same subject could yeild up to an f/8.5 cumulative meter reading (depending on how much the lights overlap).

That makes sense lol

I am new to lighting so I wasn't really expecting such a simple answer.. It makes so much sense now that I think about it :)

Thank you so much.

Note I edited my original comment as you were responding.

Do you use a light meter? This should be easily done if so.

If you don't have a meter, this is much more complicated, as well as hit/miss.

Imagine for a moment that you have two of the Einsteins, but no meter. You could very simply set one at half the power of the other, but that is still not the whole story. For the ratio to work both lights would need to be at exactly the same distance from your subject, using identical modifiers. If one has a softbox, one has a reflector with grid, well, it isn't apples to apples any more.

Now, since you have two entirely different light sources, you can see the problem right away.

So, let's say my meter just died. I have to get this shot with the ratio described. Thinking out loud, here: I would set up the main light, and have a stand in hold a gray card. I would set my camera to f8 and shoot the card, check my histogram, and adjust my light up or down until the spike was in the middle of my histogram. Then I would turn the main off, turn on the second light, set my camera to 5.6, and shoot/adjust as described until the spike is in the middle again. Then I would turn on both lights, set my camera to f8, and I should be pretty close. Keep in mind that any movement of either light toward or away from the subject will alter the ratio and exposure.

But a meter will make this much easier. I use the Sekonic L358, like it a lot.

I've got the Cyber Commander and I've been using that for metering so far.


Thanks for the help.

I think its worthwhile to have a baseline exposure for each of your flash units.

The procedure I use is to set the unit's power in the middle of the range, place the unit 8 ft from a Color Checker (the PassPort is a nice version) Set camera to ISO 400 with shutter speed at x sync speed and lens at F8 Now make an exposure. Look at the LCD on the camera with the chipping blinkies turned on. If the white square is blinking stop down the lens one stop and shot another. If there are no blinkies open up 1/3 stop and reshoot. If no blinkies open 1/3 more. Blinkies starting, then the proper exposure is 1/3 stop less than the current setting.

Now you know that that flash at 8ft, no modifier, gives F8 1/3 at ISO 400 in the middle of its power range.

With this information you can quickly estimate what settings are required for a different exposure, distance or by adding a modifier.

It also makes it easy to determine how much light a modifier absorbs using this method as well.