Reply #14 - April 08, 2007, 07:18:32 PM
The Fill Light.
The human eye has a very wide dynamic range. In bright sunlight we can see details in the darkest shadow and the brightest highlight. A photographic negative, since we view it by transmitted light will still show some detail in the extreme ranges- the sensor in your digital can recored a somewhat limited range if you check the histogram on the camera's viewing screen. When images are finally printed on photographic paper, because prints are vied by reflected light, have a far narrower range. To render a full range of tones in the final print it is necessary to compress the range of the scene to fit the paper's limited range. One of the steps in this process is to have fine control; over the lighting ratio as seen on the subject. this especially applies in portraiture. When a portrait is made in direct sunlight or indoors with a spotlight or a raw flood light with a smaller parabolic reflector the difference between the highlights as compared to the shadows will be very wide- perhaps a ratio or 1:10 which is way out of range for the aforementioned process.
The sun or the studio lamp will shape the face and create the illusion of dimensionality, the creation of modeling, as some photographers call it. This is because the main light source such as the sun or a studio lamp is placed off the camera/subject axis in order to create light and shadow. Since we know that the shadows will render little or no detail, the next step is to bring in the fill light. The light source's job is to pump some light into the shadows to lessen the ratio thus compressing the range for the photographic paper.
Since we have only one sun, things look natural to us where there is one direction of light. If the presence of the fill light becomes appearant in the form of a secondary shadow or a second catch light in the eyes we get a disunity of light which looks unnatural. Therefore, the effect of the fill light should be "invisible" It is usually a FLAT light source which is placed close to the camera so that it does not create shadows of its own. It can be in the form of a second studio lamp or a reflector which redirects some of the main light onto the subject providing a fill light.
If I had to generalize, the fill light is weaker than the main light. Placing the fill light close to the camera and lower than the mingle light was a basic rule, however the are now many more effective methods such as bouncing lights off the ceiling of a studio room thus creating a soft blanket of light that is virtually shadow-less. There are also specialized electronic flash units that are especially designed for fixed fill light sources. Theses incorporate large troth-like reflectors and diffusion material and light modifiers such as soft boxes.
There are many other sophisticated fill methods which involves mobile fill light units- this is called form fill. To star with, knowing the function of the fill light is very important aspect of professional portraiture. Since part of its job is to control lighting ratio, it is the light that will establish the mood of the image. Terms like high key, medium key and low key are largely concerned with lighting ratio and background usage as well as color or tonal harmony.
That is the basic function of the fill light- more to come in upcoming articles.
Ed Shapiro
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Ed Shapiro
The Hintonburg Studio
Suite 201 78 Hinton Avenue North
Ottawa, Ontario CANADA K1Y 0Z8
613-792-4837 Email:
edshapiro@rogers.com
