Once you have your flash, the question is how to better use it.

Briefly, your decisions are:

• Where am I going to put the light – and why?
• How am I going to get it to stay there?
• How am I going to trigger it?
• What will the quality of the light be: Hard or soft?
• What will the beam spread of the light be – wide, narrow?
• How will I balance the strobe’s intensity with the ambient light?
• How will I balance the strobe’s color with the ambient light?

There you go. Seven decisions you get to make, with an infinite number of possibilities. And that is just assuming one strobe as a light source. Very soon, most of these variables will get to be instinctive, and you can concentrate on the two or three that will define the quality of light in your photo.

First, let’s think about what images are.

As photographers and artists we are image makers. We can make flat, two dimensional images that represent three dimensional scenes in the real world.

Another way of representing a three dimensional scene is to sculpt it; and in fact life-size realistic sculpture was one of the first expressions of thoroughgoing representational realism in Western art.

Forget colour, for now

Colour images have fundamental underlying achromatic tonal skeletons that embody all their shape and form.

We’re all at least passingly familiar with Classical Greek sculpture. We’ve strolled amongst the life-size figures on pedestals in galleries and museums. These are monochromatic now — marble-white or grey bronze — but originally they would have been painted to look more like living human figures.

Paint adds colour, nothing more. Without their paint these sculptures are not more difficult to see, it isn’t any harder to apprehend their form and volume — just the opposite in fact. And that’s a clue to what light is for in images.

Separating light values from colour

Let’s think of images as being made up of points that reflect light back to our eyes. (We’re saying images are made up of pixels.) Our vision discriminates only two fundamental properties of the light from any point: the intensity of it, and the wavelengths of which it is composed.

Our sense of the intensity of the light reflected from any point is derived from the rate we detect photons to be coming from it: how many photons per time period. We perceive this as the brightness of the point.

We perceive the wavelengths of light from the point as the colour of the point.

In colour theory, and in colour models based on human perception of colour, the property of intensity or brightness is also termed luminance. This property is a component of all colour. The measure of this property of a colour is its value. That’s to say, when we put a number on it, or some other measure, that’s a brightness or luminance value.

The term tone is very closely related to brightness. The values of areas of an image, and how they gradate, are its tones. It’s predominantly with tone, and tonal contrast, that the shapes of objects in images are delineated; and it is with tone, and tonal gradation, that their form and texture are modelled.

Colour images have fundamental underlying achromatic tonal skeletons that embody all their shape and form. When we remove colour from an image, what we are left with is its underlying tone, a panchromatic black and white version of the image. This is what a black and white image is: all the information about the brightness of light reflected from a scene, with no information about its wavelengths.

Form is modelled by how much light it reflects

It’s light that shows us the Classical Greek sculptures. It’s with light that we can see their shape and form, and get a sense of their voume in space.

Their surfaces reflect light to our eyes. Some parts may reflect most of the light falling on them directly back at us — perhaps the flat middle of a forehead, say. Others gradually reflect less light to us, and more in other directions, as they curve away from us — think of hips and thighs. There’s a gradation in the light they reflect.

Perceiving three-dimensionality

Most of us have heard that having two eyes gives us stereoscopic vision, that this is a hunter-adaptation, and that we depend on having both eyes for a good sense of distance and three dimensional vision. In fact most of us have a perfectlly good sense of the three dimensionality of the world around us, and the things in it, even when seen through only one eye.

Our instinctive understanding of perspective, and the way things should be, gives us a perfectly workable sense of relative distances and whether one thing is farther away than another.

And our instinctive understanding of gradation in the light that things reflect back at us enables us to get a near-perfect sense of their form and volume.

(Steroscopic vision is just basic range-finding on a single focus point, and adds little to our perception of the world. It might help you catch a ball, but it won’t improve your sense of how round it is.)

This is one of the reasons why we can appreciate the illusion of flat, two dimensional images as a satisfyingly realistic representation of the real world.

Coming back to colour

Classical greek sculpture is a high-point of realistic representation of the human form. When time removed the statues’ paint it allowed the underlying art of the sculptur to shine through — in a heightened, slightly hyper-real way — and it showed that aspect of it in a degree of isolation from the final statue considered as a whole. It’s not unlike what happens when a photographer makes a panchromatic black and white image of our, in-reality coloured, world.

Does the superficial surface matter? If we re-apply the paint, does it change the apparent form and volume of the statue? No. It might change the texture of the surface, and we do have a visual sense of texture. But it won’t alter how the underlying form models the volume of the figure in space. In a sense, this shines through the paint. If the statue were less perfectly modelled, and an enhanced sense of its volume had to be built up using effects of coloured paint, it would be far less satisfyingly realistic.

It is the angle of points on the surface relative to the observer that determines what proportion of the incident light they reflect to him. It’s this, not the paint on them, that models form. The form underlies the colour. Gradation in the brightness of any particular colour of paint we see on a statue is caused by the underlying forms beneath it, not by some property of the paint itself. The underlying form modulates the brightnesses we perceive, and this models the volume of the statue for us.

Still images

Classical Greek figures have something further in common with photographic images (and paintings): they are still. It’s interesting that their stillness often captures a moment of the figure in motion. The sculptor hasn’t just frozen a moment; he has carefully chosen to freeze the exact moment that most wholly represents and expresses the entire movement.

Becoming flat

In Classical times, and for long after, sculpture was the pre-eminent visual art. Painting images on flat surfaces would not even begin to rival it for many centuries. But there were flatter forms of the sculpted image. Figures sculpted or modelled in relief appeared on friezes and other features, like bodies half-emerging from the clay or stone.

We can’t walk around them, they are tableaux with a single definite (rather than implied) picture plane; but their shape and form are still modelled in three real-world dimensions, even if the third one lacks depth.

If we can flatten these reliefs completely we’ll have arrived at realisticly two-dimensional images of our three dimensional world. But we need to represent or simulate the way light is reflected differentially from forms, or gradates on them. We need to shade them in.

In photography you can learn to apply lights, natural and artificial, by rote. That’s to say, you can learn the set-pieces, the standard set-ups, in what circumstances and for which types of work to apply each one.

But some of us don’t learn well by rote. We need an explanation of the fundamental principles at work in lighting. And some of us would find a fundamental understanding of light and lighting more satisfying, particularly if it becomes so much second nature that we learn to apply it naturally, fluidly expressing elegant lighting solutions for each scene that we shoot, drawing simply on fundamental principles.

The medieval master mason was able to draught the plans for his cathedrals, and scribe the templates of their carved stones, using just simple compass and square, applying his fundamental knowledge of measure and proportion, step and repeat.

So let’s start learning what light is for in images, what it does and what we can do with it.

Next: Theory of light 2: modelling three dimensions

studio lighting equipment

One-light portraiture: “The beauty of working with one light source is the simplicity of what-you-see-is-what-you-get. So many photo shoots within the studios get so complex really really quickly, and what we want to talk about is simplifying our lives a little bit. So we’re going to go through a series of one-light portraits.

For the first one I’m going to move a light in really close to the background, almost touching the background. This is going to do a couple of things. I’m going to be able to be clever enough to let this light also light my background and my subject. It gives us a nice gradation, eliminates any shadow from the model, and really makes a nice one-light quick set-up.

The second one-light set-up that we did was very simple: it was one light set at 45 degrees to the camera, 45 degrees up high, and a reflector. It was a real simple shot. You’ve got to make sure that the reflector is forward enough so that it picks up where the main light stops off. If you look at the samples with the reflector and without the reflector, what you notice is that the reflector does make a tremendous difference.

The last of the one-light set-ups that we did is unique because it showcases the ability to make one light look as if it were three. I start by removing the softbox, and I create a situation where this one light source can become my main light, my background light, and my fill light all at the same time. I drop translucent fabric in between the light and my subject, that lets direct raw light skim past and light up the background. I bring in a reflector in front of the diffuser and use that as my reflector-fill, almost as a fill light.

Once you conquer one light, and once you can create a lot of different looks with one light, you can conquer anything.

The more lights we add, after we go past that one-light, it becomes more complex. Everything becomes a little more difficult, and you have to think through how everything might affect each other.” –Tony Corbell

two light portraiture

Two-light portraiture: “The interesting thing about working with two lights is the ability to not just separate the main light from the background, which we were able to do with one light, but now we can separate them and control them, and that’s totally different. On the second two-light set-up we’ve got a main light coming from on top and a fill light coming from below. This is kind of like a glamour set-up, some people call it clam-shell lighting. The beauty of this is that it really accentuates cheekbones.” – Tony Corbell

three light portraiture

four light portraiture

Four light portraiture: “I always start with my main light. That’s where my first exposure reading is taken. I establish that foundation, and then everything is then relative to that: my background lights are either brighter than that or darker, and everything is relative to that one main light. In order to keep detail in highlights you need to make sure that accent lights and any light coming forward is at least one / one-and-a-half to two stops below what you’re shooting at.” –Tony Corbell

“We can put the light over here, we can put it here, we can put it just in front, on the back: it changes completely. Any cinematographer, using this kind of light, can tell a story, can write with light.”

“There are three things that lighting has to do: it has to provide for sufficient illumination to record the image on film; it has to make up for the difference in contrast between our eye and the film; and it has to enhance the illusion of third dimension in a two-dimensional medium.”

“You walk on a set, it’s absolutely black, and you strike your first light for what you’re going to do, and that becomes your first brush-stroke. And then you add other brush-strokes all the way through, add different lights, till you come out with your complete picture. And then you look at it and say ‘OK, let’s do it!’.”

“I walk onto a dark stage usually I turn on one light. This light hopefully has been there before, I put it there earlier because I hopefully know where the light’s coming from in the scene. And then I decide what does that look like. And that’s theoretically the light that’s coming in the window, or the light that’s coming from the main lamp in the room, or something, and I’ll start with that. And the other lights all should be in place, then I’ll turn them on. I don’t turn on all of the lights at once. Usually I turn them on one at a time, and then I start turning them off again.”

“Usually when I show up on a set and get ready to shoot, I’ve already lit the set in my head.”

“My favourite thing in using light, for instance: I like relativity, I like light-to-dark, big-to-small. My favourite kind of thing is you have somebody standing by a window talking to somebody who’s standing in the corner. And someone standing in the corner is in the dark. So you’re cutting from this guy at the window talking to this girl who’s standing in the corner in the dark.”

“There are three things that lighting has to do: it has to provide for sufficient illumination to record the image on film; it has to make up for the difference in contrast between our eye and the film; and it has to enhance the illusion of third dimension in a two-dimensional medium. OK, that’s what it has to do; what it can do…”

“It can affect you emotionally, it can help tell the story. You have to know what story you’re telling before you even start to think about how you light it. And you have to think about whether you want the audience to see everything clearly, or whether you want to hold it back a bit from the audience, whether you want to throw the actors into a little bit of shadow.”

“Not adding, but taking-away is better, always. It’s like something’s not working, you throw another sand bag in the boat because it’s listing, and you keep throwing sand in till pretty near the whole boat sinks. You don’t put in more, you take away. Usually when something doesn’t work it’s because you’re doing too much, or you’ve made the wrong choice.”

“I remember when I first started out as a cinematographer the very first thing I was into was is there enough light.”

“Light can be flat or not-flat, and clearly flat is not good.”

“It’s not just to look at the screen. You’ve got to make the audience look at a some part of that screen that’s important, where the dialogue is going on.”

The Strobist “Lighting 101” blog thread is probably the best place to start when you first decide to move your flash off-camera. And it’s not a bad place to start learning about lighting in general. Really very highly recommended.