Deconstructing light, part one: one light

Over the next few days, we’ll look at a few examples of lighting, and specifically, deconstructing it: what lights were positioned where, and what was the logic of doing so?

Today, I’m going to start with some relatively simple setups: they only use one light, with or without additional modifiers. Quite often, you don’t actually need much more than that. Single light setups tend to have very well defined shadows and highlights; chiaroscuro is the term that’s used to refer to an image that is predominantly described by it shadows and negative spaces. Classical painters were masters of this technique; they lit things in ways that are very difficult to replicate in real life – partially because of the size of their sources, and partially because they weren’t strictly limited by the laws of physics.

For simplicity, let us assume that you’re shooting at your camera’s highest sync speed, and that ambient light is not really a factor into the equation. Note that everything said here applies to both speedlights and studio strobes. I’m not going to discuss built in or on-camera flash, because it simply will not give you the results you need or offer the flexibility required. There are few variables in a one-light setup:

1. Output power
How bright do you want it? Usually, your lights will alter power based solely on your desired depth of field – which translates into aperture, which in turn translates into the amount of power required to provide a correct exposure. Note that the shutter speed only affects ambient light, not the power output of the flash. Flash duration is often 1/1000s or even much shorter. Most cameras will sync to 1/250s or thereabouts; this is the maximum duration of a full power flash. Those that sync at higher speeds require the flash to fire several times to cover the focal plane, as this is the highest speed at which the entire sensor area is exposed at the same time. (Anything faster, and the opening between shutter curtains is effectively a narrow moving slit.)

2. Distance
More distance requires a higher guide number to provide the same given illumination. Distance also affects the perceived size of your source – in general, providing the light isn’t a single point, the farther away you are, the brighter your source has to be for a given illumination level. For more diffuse light, you want your primary source to be further away.

3. Beam coverage/ angle
Most flashes and heads can have their beam angle changed – you want to match the beam angle to the focal length to produce the optimal balance frame coverage and power consumption; lighting more than you need to is a waste of power, but less than your angle of view will produce hot spots. Of course, you could always do this deliberately for a spotlight effect. Note that a wide beam close to the subject and diffuser will not look the same as a spot (telephoto setting on the flash) beam farther away with a big diffuser; the latter will produce far softer light.

4. Diffusion
The best example of diffusion is the difference between a clear, cloudless day and an overcast one: look at the difference in shadows. A cloudless day produces very harsh shadows and wide dynamic range with high brightness in the highlights; it’s a dynamic range nightmare (especially for outdoor wedding shooters, because of all that black and white involved). The opposite is true for cloudy days – note how soft and diffuse the light is. The clouds are effectively adding as a diffuser. For photographic/ flash purposes, you can use a diffuser – not a small clip-on thing that goes on your flash, but something larger like a softbox. The further away your source is from the diffuser, the softer the light is going to be. Control diffusion, and you effectively control the subject’s tonal differentiation.

5. Angle of incidence/ positioning
This seems obvious, but where you put your light and how you aim it can make a huge difference to the look of the image. In fact, it’s possible to leave the orientation of subject and camera fixed in one position, and just move your lights to create several completely different-looking images.

A quicks note on color and white balance: assuming all of your exposure comes from flash, just set your white balance to flash or daylight – most cameras will do this automatically. We do need to start worrying about mixed color temperatures, but only when balancing ambient and artificial light.

Let’s look at some examples.

Hair. Leica X1

Single speedlight in softbox; shot at 1/2000s sync speed – to freeze motion, I used a camera with a leaf shutter and high flash sync speed. The source was positioned at 45 degrees to the subject and camera to provide definition; it was not that far away from the subject to avoid too much diffusion – this way, you still get some highlight definition which helps give the subject shape.

Maitres du Temps Chapter 3 prototype dial. Nikon D800

Single speedlight behind diffuser panel to the top of the watch. The watch was inside a diffuser box to control reflections of surrounding objects off its polished surfaces. For images like this, the precise position of the flash relative to the diffuser and subject, as well as the beam angle, are very important – a small change in the position of the flash or beam angle changes the nature of the reflection significantly, as you will see demonstrated by the next image. For this image, the source was reasonably high up, far away, and with a wide beam angle to produce a soft reflection.

Lange Datograph. Nikon D700

This shot employed an almost identical setup to the previous one, except the flash was at a lower angle, much closer to the watch and with a tighter beam spread (longer zoom setting). Note how the reflection in this shot is very concentrated in one spot close to the top edge of the crystal, and is much ‘harder’ and more defined than in the previous shot.

Seasoning. Nikon D700

I used a flash in an reflective umbrella to the back left of the subject here; I wanted some diffusion but also some definition – too much diffusion and the pasta looks like a flat, matte amorphous blob. The source was partially behind the subject to provide a bit of backlight, which would define the grains of seasoning against the dark background of the person’s shirt. Note: there is such a thing as too much diffusion!

Girard-Perregaux F1-047. Nikon D700

Despite appearances, this shot actually employed direct flash with almost no diffusion. The watch itself is fairly matte, and the texture of the carbon-fiber dial is only apparent when struck with strongly directional light. I used a single flash to the right of the subject, almost touching the diffuser panel; this provided a minimal amount of softening of the edge of the flash source (so it wouldn’t appear as a hard point source in the minor reflections) but enough directionality to give the dial definition.

Prawns. Nikon D700

This example involves one flash again, but bounced off an umbrella fairly far away from the subject. Given that the room, tablecloth and surroundings were predominantly white, any light source used would reflect and provide some fill. This meant that the primary source had to be diffuse, yet directional – making an umbrella ideal.

Eugenie. Nikon D200

The final example involves a combination of light modifiers – a snoot and a diffuser box. The snoot was used to concentrate the light to the center of the diffuser; the diffuser was used to soften the skin of the subject. The net effect was a soft spot – imagine a source about the size of a large dinner plate, with intensity dropping off towards the edges. Thus, we get the best of both worlds – chiaroscuro definition, and gentle tonal rolloff in the shadows and highlights.

Come back tomorrow for part two. MT

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