Paul C. Buff, Inc. Technical Forum

Hi, this will be my first use of Einstein and I am going to shoot a model against sunrise. I do not have a flashmeter, is there an easy way to balance the ambient light and flash light on the subject?

The easy way would be with a flash meter. However, you can look here for guide numbers and measured apertures at full power for various modifiers: http://www.paulcbuff.com/output.php These measurements are at ISO100.

Guide numbers will help you find an aperture based on distance, or distance based on an aperture.
So with a guide number of 110, divide that by 10 (feet) and you get (f/)11.

If you use a softbox, that is a GN of 102. At 5ft, that is f16 and 7/10 (a.k.a f/20). If your sunset meters at f/8 (from your camera's meter), then you will dial the light down 2 and 7/10 of a stop to match the f/8.

This is slightly simplified, but it will get you in the ballpark.

Assuming your shooting digital, you can use your camera meter to get a good exposure in manual.

Set your camera up for 1/125 sec and set your aperture to get a good ambient exposure. ISO can be adjusted to 100, 200, 400, whatever you like that works for available light and depth of field you want.

Now kick your shutter speed up to 1/200 or 1/250 sec, whatever is your max sync speed is on your camera. Now play with your flash power till you get the lighting you like on your model, watch your histogram to make sure your not washing anything out.

Now you can put your shutter speed back to 1/125 and you will have a balanced light from ambient and flash.

Now you may want to kick up your shutter speed up a 1/2 stop to bring more attention to your model than the background if that is what you want. Remember, shutter will change ambient exposure but will not affect flash exposure. Only ISO and F/stop will affect flash exposure (and flash power of course).

That being said, this process will take 5 or 10 minutes, maybe more, losing light to a falling sun fast. A flash meter is expensive but makes this process much more efficient. If you find you enjoy and do a lot of outdoor studio lighting, you might want to start a change jar to save up for a good meter. I have both paul buff's and sekonics, I prefer by far the sekonics. Buff's is a powerful meter beable to control more lights than anyone would ever use, it's just too complicated for a simple light setup. Just my opinion...