The nature of light

Article and Photography by Ron Bigelow

It is very instructive to take note of what issues top photographers tend to write and talk about. For these are likely the issues that these photographers consider critical to their success. This being the case, the one topic that I see covered by top photographers, time and again, is the topic of light. The nature photographers often talk about seeking out certain light conditions or only shooting in specific types of light. The portrait specialists often discuss the lighting set ups and how it affects the final image. Even the photojournalists and travel photographers talk about trying to catch people in light conditions that best exemplify the people and the environments in which they live.

If light and its qualities are so important to top photographers, it would behoove us to examine light and understand its influence on our photography. Therefore, the purpose of this article is to look at light, its characteristics, and how it influences our images.

The Triple Nature of Light

Knowledgeable photographers will tell you that light has a triple nature for the photographer: color, direction, and quality. It is these characteristics of light that determine how our images turn out. It is an understanding and mastery of these characteristics that is often, at least partly, responsible for the best images that we see.

Color of Light

In 1665, Sir Isaac Newton was able to show, by using a double prism experiment, that ordinary, visible light is actually composed of seven colors (red, orange, yellow, green, blue, indigo, and violet). We now know that visible light is actually a continuous color distribution that starts with red light at the long wavelength end of the spectrum (wavelength has to do with the electromagnetic properties of light and refers to the distance from one crest of the electromagnetic wave to the next; if that doesn't make sense, don't worry about it) and ends with violet at the short end. In reality, visible light is only a portion of the light spectrum (light continues with infrared at one end of the spectrum and ultraviolet at the other).

Pure, white light is composed of a balance of these colors. However, light is not always pure. Often, the color balance of the light has been altered. Most frequently, this occurs because one or more of the colors have been, at least partially, filtered out of the light. When this happens, the color of the light changes. Because of this, the light that we experience is constantly changing color all day long and this affects the color balance of the images that we take. As covered in my article on advanced composition (Advanced Composition -- Part II) color affects the mood of an image. Consequently, the color of the light that illuminates a scene will impact the mood of the image and its ability to impart what the photographer wanted to communicate to the viewer of the final image. This works to great advantage for the knowledgeable photographer that uses her knowledge of light color to capture images where the color of the light is in harmony with the mood that the photographer wishes to create in the image. Conversely, the light often works to the detriment of the less knowledgeable photographer to contradict the mood that he intended to create or, at best, leaves him with an occasional, lucky image that impresses his friends but which he can not replicate due to his lack of understanding of the effect of the light on the emotional impact of the image.

Luckily, for photographers, we can simplify the color of light down to three basic categories of color: neutral light (no strong hue), warm light (tinted with yellow, orange, and red), and cool light (tinted with blue). We can simplify color down to these three categories because each of these categories has a different effect on how people respond to an image.

Figure 1: Neutral Light

Neutral light, which has no strong hue, is best used when a photographer wants the natural color of the objects to shine forth.

Figure 1 shows an image that was taken under fairly neutral light conditions. Under these conditions, the light did not add any significant colorcast to the image. This was desirable in this wave image. The white of the foam is critical to this image, and it was necessary to capture this white without any hue being introduced by the light. The use of neutral light allowed this to be done.

Neutral light is found away from both ends of the day (not in very early morning or in late afternoon). Light from a direct, overhead sun on a clear day may have a fairly neutral color. Photographers that wish to use neutral light need to beware of certain conditions. Heavy cloud cover will likely shift the color of the light toward blue. Also, shadows generally have a bluish tint. Light that is filtered or reflected in any way may pick up a hue. For instance, a photographer standing in a forest will likely find that the light has picked up a green hue from the leaves overhead. A photographer in a canyon with light reflected off the canyon walls will likely find that the light has picked up a color from the walls (probably a warm tone).

Warm light is good for creating inviting, dreamy moods in an image. People tend to associate warm light with feelings of comfort, friendship, and romance. The roaring fireplace that two lovers sit by casts a warm light on them. A husband and wife celebrating their anniversary eat dinner at a table illuminated by the warm, flickering light of a candle.

Figure 2: Warm Light

Figure 2 shows an image that was taken under conditions of warm light. At the time this image was taken, the sun had dropped low on the horizon and the light had developed a warm tone. This warm tone is most noticeable on the face of the cliff with the waterfall. The warm light gave the scene a gentle, enticing mood. The importance of the color of the light used to create this image can not be over emphasized. The waterfall in this image is the McWay Falls in Big Sur, CA. It is reported to be one of the most photographed waterfalls in the state. I have seen images of this waterfall from several professional photographers, and every single one of those images was taken in warm light conditions. In other words, for this and many other successful images, having the correct color of light is not something that is desirable; it is something that is mandatory.

Warm light is best found just after sunrise or just before sunset. This is because of the interaction of light and air molecules. Air molecules scatter the short wavelength blue light more than the long wavelength red light. Just after sunrise and before sunset, the sun is low on the horizon. This causes the sunlight to travel through more of the thicker air near the earth (the air gets thinner the higher one goes in the atmosphere). As a result, much of the blue part of the light is scattered. This leaves a warm light.

While the warmest light will generally occur within about a half hour of sunrise and sunset, the light can, sometimes, begin to pick up a warm tone a couple of hours before sunset (my experience has been that the light tends to lose its warm tone fairly quickly after the first half hour of sunlight in the morning). My experience is also that the late afternoon tends to produce warmer light than in the morning. Photographers that wish to use warm light need to watch out for clouds and shadows; both produce a bluish light.

Cool toned light is good for creating feelings of calm or cold. People tend to think of deep, calm lakes as being blue. A calm sky is usually blue. On the other hand, people also tend to associate blue with cold: ice may have a blue tint as well as the light of an early, winter morning.

Figure 3: Mixed Cool and Warm Light

Figure 3 illustrates the use of cool light. Actually, this image illustrates a mixture of light. The clouds low on the horizon display the very warm light of the last few rays of sunlight. However, the ocean has already fallen into the shadow of evening. The ocean is dimly lit by the sky above that has cast a cold, blue calm over the ocean. This contrast of light adds impact to the image. This image represents the dividing line of the day: the warm of the sun departing as the cold, ocean wind begins to chill the night air.

Cool light can often be found in the time between the first light of day and sunrise as well as between sunset and darkness. These twilight times often cast a soft, dim, bluish light over the terrain. Sometimes, a mixture of light is created at these times (as in Figure 3). Blue light can also be found under cloudy skies and in shadows.

Cool blue light is caused by the same phenomenon that causes warm light. Remember a few paragraphs back it was stated that the air molecules scatter the cool, blue light more than the warm, red light. This explained why the light just after sunrise and before sunset was warm, but what happened to all that blue light that was scattered? It was scattered into the sky. This is why the sky is blue. It is due to the scattering of the blue part of the light spectrum (this scattering happens all day long; it is just more pronounced during the very early and very late portions of the day).

During the twilight times, the sun is below the horizon. The landscape is illuminated by the sky alone. The light from the sky has a blue tint due to the scattered, blue light. This is also why the shadows are blue as they get most of their light from the sky rather than light directly from the sun.

Color and Saturation

There is another aspect of color that is important to the photographer: saturation. From the photographer's point of view, saturation refers to the intensity of the color. A color that is very vivid is a saturated color. Colors that appear dull or washed out are unsaturated colors. From a technical viewpoint, saturation refers to how much white light is mixed in with the color. Saturated colors contain very little or no white light. That is why they are very vivid. Unsaturated colors have been diluted by the addition of white light.

Figure 4: Saturated Colors

Figure 4 shows an image with saturated colors. The colors are fairly vivid and pleasing to the eye. In particular, the reds, oranges, and yellows of the leaf stand out. The objects in the image are actually rather mundane; it is the saturated colors that define this image.

Figure 5: Desaturated Colors

Figure 5 shows what an image with desaturated colors looks like. In particular, the greens of the grass and bushes are relatively washed out. This is a result of the image being shot in unfavorable light (yes, I know better, but I was hiking through this area at mid day and decided to take an "I was here, too" shot).

Since color affects the mood and impact of an image, saturation becomes important. Often, photographers want rich, intense colors. Sunsets are an example of this. The best sunset images contain very saturated colors. Therefore, photographers need to understand what factors can be used to control saturation.

One of the biggest factors that affects saturation is time of day. Early morning and late afternoon generally provide more saturated colors than mid-day. If you look at the landscapes of some of the most successful photographers, you will find that most of their images were taken early or late in the day, partly, for this reason.

A polarizer filter is another way that can be used, in many situations, to increase the saturation of colors. Part of the light that dilutes saturation is polarized light. Polarized light is light that vibrates only in one direction (this has to do with the electromagnetic waves of which light is composed). A polarizer can reduce the amount of polarized light and improve the saturation of the colors. However, a polarizer is not equally effective under all circumstances. A polarizer has the greatest affect when the camera is pointed at right angles (perpendicular) to the direction of the sunlight.

Figure 6: Optimum Polarizer Angle

Figure 6 shows the optimum positioning of the camera, in relation to the object to be photographed and the sun, for the maximum polarizer effect. As the camera moves away from this perpendicular position, the affect of the polarizer is reduced. If the light is coming directly from behind or in front of the camera lens, the polarizer will have no affect at all.

Polarizers can cause problems with wide angle shots. With wide angle lenses, the angle from the camera to the objects changes, relative to the direction of the sunlight, depending on where the object is located in the wide field of view. Thus, the polarizer will have a different affect on different parts of the wide angle image. A typical example of this is a wide angle shot of a landscape where a polarizer was used. The saturation of the blue in the sky may change across the sky due to this polarizer affect.

Another factor that can affect saturation is exposure. An image may get different amounts of saturation depending on how much exposure is given. For instance, photographers that use slide film often underexpose by about a half stop to increase the saturation of the image. The affect that exposure has on saturation varies depending on what film/sensor is used, the color, and other factors. This makes it difficult to predict the impact that changes in exposure will have on saturation. The best advice is to bracket the exposures. Then, pick the best image from the bracketed exposures.

Color and the Human Brain

When dealing with the color of light, certain matters need to be kept in mind. Probably the first issue is the human brain. It turns out that the human brain does not passively receive or passively process sensory information. Instead, the brain does a significant amount of data altering before it allows the human that owns it to perceive. Quite often, the altering that the brain does changes the reality that the human perceives. A couple of examples will illustrate this point. Years ago, the professor of a psychology class that I was taking in college talked about an experiment that had been done. A person was fitted with a special pair of glasses that turned everything upside down. Obviously, this made it very difficult for this individual to function -- everything the individual saw was upside-down. However, the individual did not have to endure the situation for very long. After a certain period of time, the individual's brain turned everything right side up again. In other words, the individual was receiving an upside-down image on the sensory cells in his eye, but the brain was inverting the image so that he would see correctly. The second example involves skiing. Years ago, I used to snow ski. I wore a pair of ski goggles that had a very bright yellow lens. When I would put the goggles on, all of the snow covered countryside would turn bright yellow. However, after skiing a short time, my brain adjusted the yellow color out so that everything was white again. In short, I was seeing through a yellow filter but the brain was adjusting the color to turn everything back so that it appeared normal.

As can be seen from this last example, among many other things, the brain adjusts the color that we see. The vast majority of the time, we are not even aware that this is happening. For instance, when you walk from a parking lot into a building, you are probably not even aware that the color of the light has changed significantly. For photographers, this creates a problem: the brain monkeys with the color we see. Thus, we do not always see color correctly. In particular, when dealing with warm or cool colored light, the brain functions on a principle of constancy. It expects the colors of objects to remain fairly constant throughout the day. If the color of objects changes during the day because the light that is illuminating them changes, the brain tends to filter out at least part of that color change (remember the yellow goggle story). As a consequence, the color that we see during times of strong warm or cool light tends to be less intense than the color of the actual light and, possibly, less intense than what the camera will see and record. For instance, a casual photographer may not be aware that the light has become warm toned in the afternoon until he gets his film back and discovers that his wife's skin has an odd yellow tone.

So, if we can't trust our eyes, what is a poor photographer to do? There are a couple of answers. The first answer is to stare. If you want to get a better idea of how the warm light will look to the camera, stare into the shadows until your eyes adjust. Then, look at the warm light. For a short period, you will see the warm colors more accurately. In order to see the shadows more accurately, stare at the warm light until your eyes adjust (never stare directly at the sun). Then, look at the shadows. (Galen Rowell, Color, Light, and the Magic Hour).

The second answer is to learn. The photographer must: 1) understand the color of light and what conditions produce what type of light, 2) understand how both the brain and the camera interpret that light, and 3) develop some experience in translating what he sees with his eyes to what the camera outputs. With this understanding and experience, the photographer will be able to anticipate how his equipment will handle the color of light.

Color: Getting it Right

Getting the color you want from either film or sensor is not always as easy as pointing the camera at an object and pushing the shutter release. Each film emulsion delivers accurate color only when used with ambient light of a certain color (e.g., there are daylight films, tungsten films, and films designed for other light sources). If there is a mismatch between the film and the light source, corrections need to be made, or inaccurate colors will result.

Digital cameras are a bit more flexible. They can adjust to different light sources. They do this by either calculating or estimating the color of the ambient light. However, most advanced digital cameras have more than one way to do this. The different methods may yield different results under some circumstances. While photographers need to be aware of these issues, the subject is too detailed to cover in this article. The matter will be covered in an upcoming article titled "White Balance".

Quality of Light

The quality of light is often described in terms of hard or soft light. These terms may seem a bit nebulous. If you tell a non-photographer that you took a picture in soft light, she will probably have no idea what you are talking about. Actually, there is a somewhat objective way to view hard and soft light. Hard and soft light can be characterized in terms of contrast, shadow detail, and dynamic range. In addition, although less objective, hard and soft light can be characterized in terms of the emotional response that each tends to create in the viewer.

Quality of Light: Hard

Figure 7: Hard Light

Hard light is a very direct, harsh, often unflattering light.

Figure 7 is an example of hard light. This image was shot in the desert under the mid-day sun. The result is a rather unflattering image. The sunlit earth is very bright and the shadows hold little or no visible detail. This image may be of interest to someone who is interested in old cars or car remains, but it would not hold the interest of most other people.

Hard light has a very high contrast. This can be seen very well in Figure 7. The dirt in the sunlight is very bright almost to the point of being uncomfortable. The dirt that is in shadow is very dark. Furthermore, the dividing line between the sunlit and shadow areas is very sharp, almost knife like. At no point in this image is there a smooth transition from light to shadow. The changes are all abrupt.

Hard light tends to lack shadow detail. As can be seen in Figure 7, it is very hard to see any detail in the shadow areas under this hard light. One could bring out the shadow detail with some extra exposure, but that would make the sunlit dirt even brighter. This lack of shadow detail is related to the large dynamic range of hard light. Dynamic range is a measure of the span of tonal values over which a device (in this case a camera) can hold detail. In other words, it is the tonal distance from the darkest point at which the device holds detail to the lightest point. Dynamic range is measured in stops of light. When light is increased by one stop, the amount of light is doubled. (going in the other direction, it is cut in half). Color print film and the better digital cameras have a dynamic range of about five or so stops. That means that the brightest areas in which they can hold detail are about 32 times brighter than the darkest areas that hold detail (each stop is a doubling of light, so five stops = 2 X 2 X 2 X 2 X 2 = 32). Color slide film only has about three stops of dynamic range. Unfortunately, an environment illuminated by hard light can have ten or more stops of dynamic range. In other words, your camera can not capture all of the detail (unless you are shooting with black and white film some of which can have a dynamic range of around ten stops). In hard light conditions, either the highlights or shadows will likely lose detail when photographed in color. Generally, experienced photographers prefer to lose detail in the shadows rather than the highlights -- thus, the lack of detail in the shadows in hard light conditions.

Hard light generally creates feelings of harshness or starkness. Often, this is an uncomfortable feeling. This can work to the detriment of the photographer. For instance, a beautiful flower shot in hard light conditions will not look very attractive. Part of this is due to the harsh contrast and dark shadows. Another factor is the fact that hard light generally tends to desaturate colors. So, in addition, the flower will have washed out colors.

Figure 8: Hard Light

However, this does not mean that hard light should never be used. Hard light has its place. Hard light can be used to emphasize harshness or starkness. For instance, a photographer may choose to shoot a desert scene in hard light in order to emphasize the harsh nature of the environment. Figure 8 is a case where the photographer deliberately chose hard light to accentuate this desert grave and its harsh environment.

Hard light is created when a scene is illuminated by a small light source. Direct mid-day sun is a typical example. While the sun may be very large, it is also very far away and appears to be small to a person on earth. Thus, direct sunlight that is not filtered or reflected in any way tends to be hard. As a result, photographs taken in clear sky conditions during the day will exhibit the typical traits of hard light.

Quality of Light: Soft

Figure 9: Soft Light

In many ways, soft light is the opposite of hard light. It can be a very diffused and flattering light.

Figure 9 shows a photograph taken in soft light conditions. This image required a soft light to create the mood the photographer wanted to capture. The image required the gentle blending of light into shadow that occurs among the petals. In addition, the colors are enhanced by the soft light.

Soft light has low contrast. The bright areas and shadowed areas tend to blend together more easily than in hard light conditions. The transitions between sunlit and shadow tend to be gradual, rather than the knife edge effect often seen in hard light.

Soft light usually has decent shadow detail, as can be seen in Figure 9. This is due to the fact that soft light frequently has a smaller dynamic range than hard light. Under soft light conditions, a photographer has a better chance of capturing the entire dynamic range of the scene with her camera without having to sacrifice detail in the shadows.

Soft light tends to create a feeling of comfort. It is the type of light used most often in landscape photography to enhance the feeling of beauty of an area. In addition to the gentile blending of light and shadow, soft light usually produces more saturated colors than hard light.

Soft light is created by a large or filtered light source. A hazy or cloudy sky will produce soft light. Light reflected off of a surface often becomes soft. Light that is filtered by a lot of atmosphere is soft. This is one of the reasons that cloudy or even rainy days are good for flower photography. It is also one of the reasons that much of the best landscape photography is done at the beginning or end of the day. The light has been softened by the extra atmosphere that the sunlight must pass through at that time.

Direction of Light

The last characteristic of light is direction. Specifically, it is the direction of the light with respect to the direction of the line from the camera to the object being photographed. There are three primary directions of light: front, side, and back. Each of these directions of light has its own characteristics and has an impact on the mood that an image projects.

Direction of Light: Front

Figure 10: Front Light

Frontlight hits images head on (from the front or overhead). It is less used in good landscape photography and more frequently used in bad.

Figure 10 shows an example of frontlight. In this case, as is often the case with frontlighting, the light produces a rather uninteresting scene. As can be seen in this image, frontlight tends to produce flat looking images -- the texture of the objects tends to be minimized with frontlight.

Frontlighting is often found mid day. At that time, the sun is directly overhead and tends to hit objects in a rather direct manner.

Direction of Light: Side

Figure 11: Side Light

Sidelight is low angle light that hits objects from the side. It can be a very dramatic light.

Figure 11 shows the power of sidelighting. Had this image been shot in frontlight, the detail of the ripples would have been almost wiped out. An uninteresting white mass would have resulted. The sidelight brought out the detail of the dunes.

Sidelight is great for those times when a photographer wants to emphasize texture or shapes. In the case of Figure 11, texture was emphasized. In other cases, sidelight can be used to emphasize shapes. Sidelight also has an interesting affect on shadows; it causes the shadows to become very long. In some cases, these elongated shadows can be used to add drama or emphasize an object. In other cases, the shadows themselves become the center of interest.

Sidelight occurs when the sun is low on the horizon. This means that photographers can take advantage of sidelight early in the morning or late in the afternoon.

Direction of Light: Back

Figure 12: Back Light

Backlight hits objects from behind so that the light is shining toward the camera lens. It can also be a very dramatic light, but it can also create some challenges for the photographer.

Figure 12 shows the use of backlight for a sunset shot. In this case, a silhouette was created of the rock and pine trees. Silhouettes are one of the most common types of backlit shots. In the case of silhouettes, the dynamic range of the image is too great for the camera to capture (the light source is very bright while the backlit, opaque objects are in shadow). Incapable of capturing all of the detail, the photographer will usually let the shadows drop into a detail-less darkness.

Figure 13: Back Light

Figure 13 shows another common type of backlit image. In this case, the photographer chose an object of interest that was translucent. Part of the light was able to penetrate the leaf. This produced a leaf that seems to glow from within. This light accentuated both the veins of the leaf and the contrasting colors.

Backlighting is great for creating images with a touch of the dramatic. In the case of silhouettes, form often takes on more importance than detail. While the use of backlighting with translucent images tends to emphasize detail. In either case, backlighting tends to create strong mood and can produce images that are hard to ignore.

Like sidelight, backlight usually occurs when the sun is low on the horizon, but backlight has the additional restriction in that the light must be shining toward the camera. This can cause a number of problems for photographers. First, light shining into the lens can create flair. This occurs when some of the light bounces around between the lens or filter elements. If the camera has a filter on it, removing the filter may reduce the flair. Second, digital cameras don't tend to deal well with bright light sources shining down the lens. In particular, when photographing the sun, digital cameras tend to produce bizarre banding along the edges of the sun. Switching to film may produce better images in this case. Lastly, the large dynamic range of backlit scenes may prevent the photographer from capturing detail in parts of the scene in which he desires to hold detail. In this case, the photographer may resort to one of the many methods used to handle large dynamic ranges (e.g., split ND filters, fill flash, or digital blending of images taken at different exposures).

Putting it All Together

Keeping all of these various aspects of light in mind when trying to plan or create an image might seem a bit daunting. It sure would be nice if there were a time when all of the right ingredients came together to create the potential for great images. Actually, there is such a thing! To learn more, read The Magic Hour Times Two.