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Light Shaping and Modifiers
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PostPosted: Mon Mar 12, 2007 2:15 pm 
Light Shaping and Modifiers

Navigation links for topics within the page:

> <a href="#reflectors">Reflectors</a>
> <a href="#dish">Beauty Dishes</a>
> <a href="#unbrella">Umbrellas</a>
> <a href="#softbox">Softboxes</a>
> <a href="#grid">Honeycomb Grids</a>
> <a href="#snoot">Snoots, Barndoors and Gobos</a>
> <a href="#fill">Bounce and Fill Panels</a>
><a href="#modify"> Positioning Light Modifying Accessories</a>

In most studio uses, the lights will be used with some form of accessory modifier in order to achieve the desired quality of light on the subject. These typically include umbrellas, softboxes, reflectors, honeycomb grids, snoots, barndoors, bounce or diffusion panels, etc. In order to effectively use these light-shaping tools, it is important to understand the principles involved.

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Reflectors

Reflectors serve two purposes: To direct the light in a beam as desired for a given effect, and to enlarge the effective size of the light source.

For distant shooting, the size of a reflector is usually inconsequential as it will usually be too distant to have any significant softening effect or shadow control. Here, you will normally want a relatively narrow beam pattern so you can concentrate the light onto the area you are shooting.

For studio work, the size of the reflector becomes important. Larger diameter reflectors increase the source-size and consequently soften the light, thus reducing specular highlights and softening shadows. Generally speaking, the closer a reflector is to the subject, the wider its required pattern.

Shadow softening is a function of the range of angles the light projects from onto the subject. Close placements produce softer shadows than distant placements because the light comes from wider angles and produces more “wrap-around” effect.

But keep in mind, the normal reflectors that don’t contain a mechanism to block the direct light from the flashtube will always produce two shadows: the hard shadow from the flashtube itself and the softer shadow from the reflected light. This is not necessarily a bad thing because the result is effectively a small light source surrounded by a larger source. Thus, a single large reflector serving as a main light can often yield controlled, semi-soft light with added punch from the direct portion.

<a name="dish"></a>
Beauty Dishes

A beauty dish is commonly a large (15 to 30-inch diameter) reflector with a white reflecting surface and, usually, a blocking mechanism to prevent direct light from the flashtube from striking the subject. Because of the white surface, the light is very even and the beam pattern is very wide. All of the light is bounced from the white surface so that the effect is a very even, round source. Subject shadows are soft and smooth and specular highlights are diminished because there is no small, direct light on the subject. It is not uncommon to add a diffusion sock to a beauty dish to further even out and soften the light.

By positioning a beauty dish in the range of 2 to 10-feet from the subject, the degree of shadow softening may be manipulated from significant (with close placement) to modest.

Of particular interest are the catchlights or eyelights. The even, round shape of the beauty dish forms very pleasing catchlights whose size are a function of the light to subject distance.

<a name="unbrella"></a>
Umbrellas

Photographic umbrellas are the tried and true standby for shaping light. They are cheap, versatile and quite effective. Umbrellas are commonly used in one of two modes: bounce and shoot-through.

With a bounce umbrella, the light is aimed into the umbrella and the fabric bounces the light back to the subject. The actual light unit is blocked from the scene because it is pointed backwards so that there is only bounced light and no direct light (but there is a dark center because of the light unit). The shaft is usually positioned so the light from the light unit just fills the umbrella fabric for maximum source-size. It is certainly permissible to under-fill the umbrella in order to produce a smaller source size for harder shadows and higher contrast.

A shoot-through umbrella is used in the opposite mode. Here, the light faces the subject, but is diffused through the translucent umbrella fabric - consequently, there is no dark center. Depending on the beam angle of the flash unit, there will usually be a brighter center and somewhat darker edges. This is not a bad thing most of the time because it produces a variable intensity light source that reflects in the shadow and specular structure. It is generally advantageous to use a wide-angle reflector on the light unit or no reflector at all (bare bulb mode), though some sort of reflector will produce more output and less spill light around the edges.

Bounce umbrellas are typically available in silver or white fabric, and some are fitted with black covers to minimize spill light. White fabrics will produce the most even, soft lighting while silver fabrics will produce more output and slightly more specular, harder light. But the shadow structure will be similar with both fabric types because this is determined primarily by the source size.

An interesting feature of silver bounce umbrellas is their ability to focus the light into a relatively narrow beam. By positioning a silver umbrella in and out, while looking at the modeling lamp pattern, a focal point can be found where the output is the brightest and the beam at its narrowest. Thus, a focused silver umbrella is an excellent choice for lighting group of people from a distance. You can take advantage of the size itself in controlling shadows, yet you can direct the light exactly where you want it, with substantial increases in the amount of light on the subjects over white umbrellas.

<a name="softbox"></a>
Softboxes

A softbox is basically a large parabolic reflector (the sides) that directs the light onto a flat frontal diffuser panel. The light emanates from an evenly lit, sharply defined flat surface with little spill light. When shooting highly reflective objects such as silverware, wine bottles and similar objects, the softboxes produces ideal effects – similar to the light from a north-facing window. It’s not uncommon for photographers to place strips of black tape on the face of a softbox to simulate windowpanes. It’s also feasible to create masks to produce round or other shapes.

Softboxes are usually fitted with an internal diffuser panel to even out the light that falls on the front fabric. Many contain a front Velcro “lip” that reduces spill light and allows the attachment of fabric grids to further control spill.

Softboxes are traditionally rather cumbersome to assemble on location. To this end, “foldable” softboxes are becoming popular because they are set up much like an umbrella and are fast and easy to assemble and take down.

<a name="grid"></a>
Honeycomb Grids

Honeycomb grids resemble a slice taken from a bee’s honeycomb, made from strips of black metal. The hexagonal tubes that form the honeycomb direct light forward, blocking light that would otherwise travel sideways. Depending on the length and width of the tubes, the grid directs the light into a defined beam, usually with a beamwidth between 10° and 40°. This allows the photographer to selectively light only certain portions of the scene, leaving the other parts dark.

Grids are made to fit a variety of lighting accessories including small and large reflectors, beauty dishes and softboxes. They are widely used by more advanced photographers for the control of spill light and for selective highlighting.

It should be noted that grids do not focus light like narrow angle reflectors – they block light instead. Therefore, one can expect less light output from a grid, not more.

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Snoots, Barndoors and Gobos

These are also light-blocking accessories that are used to selectively shield stray light from falling on portions of the scene.

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Bounce and Fill Panels

Bounce and fill panels are not actually attached to the light unit - they are normally held by a light stand or by an assistant. They are available in many fabric types such as white, black, silver, gold and colors. They are typically used in strategic positions around the set to redirect light from the flash units onto parts of the subject that need more light (or less in the case of black) or a touch of color, etc.

A typical use for a bounce panel might be a portrait lit by a single flash unit to one side of the subject. In order to bring some amount of light to the dark side of the subject, a bounce panel can be positioned such that light bounces from the flash unit onto the dark side. This, of course, can be done with a second light unit, but often a bounce panel is a simpler and less expensive solution.

<a name="modify"></a>
Positioning Light Modifying Accessories

When using modifiers that diffuse the light source and increase its size, there is always the question: How close should it be to the subject?

In order to understand this, the user should understand the principle of light-source size modifiers.

Small-source lights (direct flash and small reflectors) project light onto the subject from a single point and narrow range of angles. Hard shadows are formed and specular features such as jewelry and eyes reflect intense small highlights. This is called “hard lighting” and results in high relative contrast and sharp features.

When you enlarge the light-source, you also decrease its intensity at any spot on the light’s surface. This causes the light to wrap around obstructions to form softer shadows. Specular reflections become larger and less bright. The relative contrast becomes lower and the picture softer. For most purposes, there is an optimum degree of softening. If your shots are too soft they can become lifeless and lack punch.

Softness is a function of the angles from which the light strikes the subject. If, for instance, a 30-inch by 40-inch softbox is placed 8-feet from the subject, the angles are the same as those from a 15-inch x 20-inch softbox placed at 4-feet. Thus, softness is a function of the source-size and the distance. This applies to all light modifiers such as umbrellas and beauty dishes. So, for a given light-source, if you want more softness move it in closer.

But there is another consideration: When the distance from light to subject begins to approach the size of the subject, those portions of the subject that are closest to the light will receive higher light levels than the more distant portions. This is accentuated due to the Inverse Square Law behavior of light. Thus, close placement will result in brightness gradients across the subject while more distant placements will provide more even gradients.

>> Click Here for more info on the Inverse Square Law

This relates to subject-background distance in the same way. If a background is, say, 5-feet behind the subject, a light placed close to the subject will provide little illumination of the background while a more distant light will provide a more equal ratio of subject and background illumination. Of course, moving lights back always results in low overall intensity and will require more flashpower or lower aperture settings.

Typical distances for softboxes, umbrellas and beauty dishes might be from 2-feet (very soft – high background isolation and strong gradients) to 10-feet (more contrast – little background isolation and faint gradients). The placement of lights, of course, is paramount to idealizing all of these parameters and establishing the mood of the shot.


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