Table Top Lighting 101: Shading and Shadows

By ron gibbs posted on

June 6th, 2012 |

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Table Top Lighting 101
Shading and Shadows (they add depth and stability)
by ron gibbs (www.theimage.com)

There are two fundamental functions which make image interpretation more comfortable for viewers. Both of these interpretations have been acquired by viewers through a life-time of experience and require no added effort on their part. Since photos are two dimensional representations of the three dimensional world, it is necessary to use and control shading to define a 3D shape in a 2D image.

Humans have learned to perceive shading and changes in shading in the real world, and relate them to changes in shape. This ability has likely been acquired through a combination of inheritance and self-training. A fast gradient change is interpreted as a edge, and an extended gradient change is interpreted as a slow gradual change of form. We know for instance that bumping an edge tends to hurt more than running into a rounded corner. Our eye’s interpret this type of shading information with real world experience. Hence we are preconditioned in many ways to see 3D objects in a two dimensional print if the proper visual queues are in place.

Shading is necessary to define the shape of an object, without shading all objects become simple outlines without physical volume. They exist only in two dimensional representations. Look at the short animation below. It begins with even, fully balanced lighting which removes all shape or volume from the objects. They appear as outline representations of standard geometric forms. They lack a three dimensional look.

After the animation begins, the lighting is changed to show the true nature of the objects. Moving them within the new lighting demonstrates that shading produces a simulation of 3D form on the flat screen display. This new lighting is unbalanced and directional.

In all types of tabletop lighting the photographer must learn to illuminate objects to create the desired degree of shading, thus making the objects appear three dimensional. A light directed from one side produces high-contrast lighting with little detail in the darker side of the image. This can be very dramatic, but may also be somewhat confusing. It tends to hide part of the shape. By using a simple reflector, it is possible to provide illumination to the darker side of an image while strengthening the 3D illusion. This is a type of unbalanced lighting where one light source provides both the full light to one side, and reduced illumination to the other. (See animation below.)

Shading is used first to define shape, then can be adjusted to increase or diminish the overall effect. It is a useful and necessary tool of the desktop photographer. By controlling the direction and intensity of light on a desktop subject we have the ability to define it’s form. We can chose to accentuate or deemphasize any part of the subject.As the last frames of the animation show, it is possible to use balanced lights (2) to maintain 3D shading without the total loss of 3d definition. In this case the darkest area appears closest to the camera. If a third light is added coming from the front, then the object will become flatter with less form and volume.

Although shading is used to define shape and volume, it is still possible to confuse a viewer when multiple objects exist in a scene. Shading provides no information as to the positional relationship of objects or their relationship to the world in general. Shadows, not shading, provides the missing key. Shadows anchor objects to the world, and may provide additional relative positional information.

Lets look at two similar computer generated images. The first is made up of a series of cubes, a cone, and a torus (blue ring). As the image first appears there are no shadows, and the user must guess what relationship the objects have to one another. There is ambiguity in this image, although there is shading information which gives the viewer the illusion of a three dimensional world, the viewer must guess how the objects are placed. The obvious (most likely answer) is illustrated in the first animation. Notice that when the shadow is added to the image, the image clarifies and the relationships are quickly understood without any additional effort.

Now look at the beginning of the next animation, it is roughly the same set up of individual objects. When the animation begins the shadows again appear, but this time there is a bit of a surprise. What appeared to be a simple stack of blocks as in the first animation is actually something far different. The shadows reveal a different arrangement which is further displayed as the animation plays out.

The first image (without shadows) in either animation is ambiguous and the actual placements of the objects cannot be determined by the viewer without additional information (the shadows). This type of ambiguity can be used to cause tension, but unless this is the desired response it should be avoided in most cases. Usually photographic images are designed to illicit a response based on content, and not their ambiguity.

Is there a substitute for a shadow? Actually there is the possibility to remove confusion by using a shadow substitute which may appear in some images. Not all surfaces are capable of showing a shadow. The more reflective a surface is, the less is its ability to show a shadow. Highly polished surfaces provide reflections, and these will substitute the needed information to a viewer. Look at the pair of images below, and notice there are now reflections which anchor the various items in the image.

Once again the viewer can determine relationship information because of the reflections and they help anchor the objects to the world in which they are displayed. Remember, the viewers do not have to be trained to use this information, and in most cases it happens automatically as it is part of their learned experience. A life time of observation has already trained the eye to the “normal” condition. Questions only arise when something is missing.

Let’s now examine a few real world photos and look at lighting to help display shape. In the first set of images I photographed a mookaite cabochon with a black jade border. (The word “cabochon” means a highly domed polished stone.) The cabochon is an oval shape with a semi-circular top or dome. The first image was created with only a single light from the left. The right side of the stone has no shape information. The second image was created by adding a reflector card on the right hand side. This card opens the shadows on this side and helps to reinforce the 3D shape of the stone. The final image was created using two lights, one from each side. There are roughly equivalent specular highlights on each side of the stone and this reinforces the rounded shape.

Next we’ll examine 3 images that show the use of a reflection, a shadow, and the lack of any reference information. The first image was photographed on a black piece of glossy plastic and displays a mirror like reflection which anchors the stone to the top of the plastic. The second image in the series shows a lightly cast shadow to the right, and it both anchors the stone to the gray table top, and indirectly shows the direction of the strongest light. The final image in the series has no reflection and no shadow, and there is no way to know if the stone sits on a surface or if floating above it. The final image was made with the stone suspended about 3 inches above the background, and was floating. Of these three images the last one appears to be in a flat world without depth.

In summary lighting can be made into a very useful ally by simply playing on the knowledge that the viewers already have ingrained. Use shading to enforce shape or texture, and use shadows or reflections to reinforce the 3D nature of the scene or the relationship between multiple objects.

About The Author: ron gibbs

I started my carrier as a wet chemist with a minor in geology. I eventually moved into computational chemistry with an emphasis on visualization, molecular animation, and digital imaging. After retirement I taught geology for one year, and now spend my time doing digital macro and micro photography, cutting gemstones, and teaching classes in Digital Photography for the Lapidary (Lapidary = gemstone cutting, jewelry making, minerals, and slabs). Yes, I use a Macintosh (since 1986) and I won't move back. I was a speaker at Macworld Expos (San Francisco, Boston, and New York) from 1988 through 2003. I have used both Canon and Nikon cameras in my carrier and like them both. I started with a Canon F1 in 1968 and now have a Nikon D300 and a D7000. (At one time I did some medium format work with a Mamiya RB67 and a Mamiya 645.) I have used Photoshop since it was in beta, and even before it belonged to Adobe, when it was originally called PhotoMat (~1989). Today I like adapting digital cameras to my microscopes and enjoy building and designing less expensive (homemade) desktop/studio photo equipment. I published a printed book in 2009 entitled "Agates and Jaspers", and it has almost sold out. I hope to begin a new book shortly on Digital Macro Photography for the Lapidary, and it will be done this time in an electronic format.