Lighting 101: Balancing Flash and Ambient, Pt 1

More than maybe anything, the quality of light in a photo comes down to the lighting ratio. On one level, it creates the whole look of your photo. On another, your lighting ratio will likely be the key variable in determining whether your paper can reproduce the information in the shadows. It's all about the shadow detail - either you want it or you don't. And you want to make the call on what reproduces in the paper.

Balancing with ambient is the same process, whether you are lighting an interior portrait or fill flashing a headshot outside. Always think in terms of balance instead of fill. The concept is less limiting. And it will not predispose you to use the sun as your main light when the strobe might be the better choice in a given situation.

I am gonna make the assumption that not every one here owns a flash meter (I have one somewhere, but I no longer use it) and give an approach that will allow you to just eyeball your way to a good balance. Flash meters are great, but they are one more thing to carry around. And if you get used to lighting intuitively, you'll find you really do not need them.

Let's start with the example of balancing flash with ambient light in a room. In this case, we'll be using strobe as the main light, with ambient as fill.

Back in your Neanderthal days, you'd pop the flash on the camera (by now, the thought, "on-camera flash: bad" should have just run through your mind,) put the aperture on f/8 and set the shutter at the camera's highest synch speed.

Great depth of field. Horrid light.

We humanoids typically light to light our interiors to about 1/60th at f/4 at ASA 400. While this may be rapidly depleting our fossil fuels and sending our global climate spiraling out of control, it works out just peachy for photographers. It is a very flexible light level, and we'll use it to run through the idea of balancing strobe and ambient.

OK, so without strobe, you'd be shooting at 1/60th, f/4, ASA 400. And there are many times when you will happily bang away without strobe. Go to 1/125 - f/2.8 if you need the speed, or 1/30th - f/5.6 if you need depth of field. But this is also an easy position from which to create a nice, balanced ambient/strobe look. And we are all about that here.

So, we're going to balance to use your strobe as the main light source, with the ambient providing the fill. Assuming you have solved your florescent/daylight/tungsten color issues (which we will tackle after we learn balancing,) you now have two, color-consistent light sources: flash and ambient.

Let's say for the sake of argument that you are going to shoot some hotshot New York designer in his apartment filled with dead, stuffed animals, as in the above photo. You throw a shoe-mount flash onto a stand and bounce it up into the ceiling at a 45-degree angle to him. Why? Because you only have a couple of minutes before the guy becomes fatally bored with you. And you want something safe that will not give you too many things to worry about. (You'll be way past this soon.)

You park him on his couch just behind his genuine, stuffed-rhino-foot planter(!) and get ready to shoot him.

Bearing in mind your original ambient exposure was a 60th at f/4, you want to drop the ambient down, say, two stops. This will create your shadows - but with detail. Assuming your camera can synch at up to a 250th of a sec, you have several choices. You can stay at a 60th and go to f/8, for depth, but your flash will have to work a little harder to put out the extra light to support that aperture.

You can keep the aperture at f/4 and go to a 250th of a sec., which might be a good choice if you are powering with AA's and/or want faster recycle times for better chance at grabbing moments.

You could split the difference and go to 125th at f/5.6. Whatever. The idea is to build an ambient-light-only exposure that would result in an underexposure of 2 stops. That will be your lighting ratio. You can choose another ratio (and you should experiment) but 2 stops is a good starting point.

So, now that you have a 2-stop-underexposed ambient photo, you simply dial your strobe up or down on manual until he looks good well lit. If this sounds a little seat-of-the-pants, it is and it isn't.

One the one hand, lighting is a little like horseshoes and hand grenades. Close enough is close enough if it looks good. You will quickly start to learn to judge what your display (and histograms) are showing you. But the advantage to working this way is that it is fast and intuitive.

And this is not to say that you want to be lazy. Fast is important because you (a) frequently do not have a lot of time, and (b) you want to get to making well-lit photos of him before you have used up all of his good will waiting for you to get your light just right. Hey, he's got stuff to design, right? So lose the idea of the Minolta meter and tenths of f/stops and learn to quickly go with the flow.

You'll light more often and your photos will look much better.

Besides, as we'll talk about later, you'll quickly get the kinda-scary ability to set your flash's manual setting very close to where it needs to be on the first attempt. I find that I am rarely more than a stop off on my first guess now. It is a very quick, intuitive way of working that fits well with the variables you need to solve when shooting an assignment.

In our case, this lighting scheme can be completely set up in about three minutes with a little practice. And that is including 30 seconds to pop few test frames to adjust the strobe's main output to nail the exposure down.

Rewinding for a sec here, we are talking about using the flash on manual, and adjusting your output up or down (usually you can do this in 1/3 to 1/2 stops) to fine tune your flash exposure. Check your manuals for your particular flash to learn how to do this. The advantage is repeatability. You nail down the light, and it flashes the same way, every time through the shoot, for consistent and predictable results.

One more thing. If you want to change the lighting angle during the shoot without going through the process of balancing (just the 30 secs worth of test popping, that is) simply keep the flash at about the same distance from the subject as you adjust the angle. Cake.


Next: Balancing Flash Intensity With Ambient, Part 2