Paul C. Buff, Inc. Technical Forum

I just recently purchased my first set of Bees...(3) AB800 units, the large octabox, and a couple different umbrellas. I am working without a flash meter, and just using my in camera meter. I have hooked up the lights with my Nikon D700 and everything seems to work just fine....I just need to know the fastest and easiest way to achieve the proper exposure. Ie: If I set my camera to shoot without the flash units (at the correct exposure), and then plug in the flash units, my exposure is obviously VERY overexposed. Is it just trial and error? Assuming I need to purchase an external light meter?
Thanks for any assistance!!!!

I'm guessing you have your camera on one of the Automatic modes (Av Tv or full auto). Put your camera on Manual. If your light meter is able to fire off the flash, do that. Use the readings from your light meter to set your camera shutter speed and aperture.

Another way is to use the modeling lamps on your AB's while you take the reading, this wont be perfect but it a good starting point.

IF: ISO=100, light is 6ft from your subject and flash is @ full power

Then: a good starting point is around f/22.

Several things will affect how much light you are getting in your exposure. ISO, Aperture, flash output, modifier (octabox), and distance to your subject. Shutter speed, not so much, as your flash is faster than sync speed.

The good thing is, most of this is predictable with math. ISO is 2x or .5x more (or less) light for each full stop change. Same with aperture and flash output. Assuming the modifier stays the same, there is no change to worry with. Distance seems hard to predict, but is not really. If the light is 2' from your subject, then you move it to 2.8', you lose one stop. Then to 4', another stop. 5.6', another stop. 8', another stop. 11', another stop. See something familiar?

Each time you move your light 1.4x further away, you lose one stop. Move it in by .7, you gain a stop.

All of this is fine and dandy, if you know where to begin (and take teh time to measure). To find your starting point, you can trial and error or use an incident meter (the Cyber Commander has a very good one, at a very reasonable cost, plus some). Ambient light meter readings (like those your camera meter provide) are worthless, as you will be adding more light than it can read. Theoretically, if you use an 18% gray card, filling the frame, and placed where your subject is, a properly exposed photo will generate a spike in the middle of your histogram (if you wish to not use a meter). 3/4 to the right is about 1 stop, far right is about 2 stops over exposed. Inverse is true with the left. Your mileage may vary, depending on camera.

Keep in mind, the above is a starting point based on theory. It assumes you want a "proper" exposure, and not a higher or lower key image. An external meter will allow you to measure ratios, measure light fall off, and is typically a faster way to work.

If you take similar/identical portraits (ala school photography), once you havea formula that works, i have seen photographers use a piece of string attached to a light stand to measure distance. Same distance, same light and settings, same ISO, same modifier, same aperture, same picture.

Wow, that was a lot... very good information, but just buy a light meter and you will be fine.

Yes, getting a light meter is very helpful, and it will tell you where you are at. Knowing the theory behind it will tell you where to go if you want a certain change, then use the meter again to tell you if you are there.