A MOMENT IN THE SUN :: TONE AND SHADOW

Spring is a wonderful time for shooting outdoors. The warmer weather encourages exploration, wandering through nature, and free expression. With spring comes bright colors, the full spectrum of greens, blossoming flowers, deep azure skies. The photographic opportunities of spring are so great as to send any shutterbug, amateur or professional, rushing out into nature at every opportunity.

When doing so, however, we do well to follow the lead of the late Ansel Adams and exercise some patience and sensibility regarding when and from what angle and perspective we photograph a subject outdoors. Not all outdoor light is the same, and the sun represents a constantly transient source of illumination that changes not only in direction but in intensity and heat. While Adams is credited as having said, "Sometimes I do get to places just when God's ready to have somebody click the shutter," he also said, "A good photograph is knowing where to stand," and "A photograph is not an accident – it is a concept." Those familiar with his work know how often he waited for hours, and sometimes days, for just the right light. Such discipline is responsible for his reputation as one of the greatest photographers to date.

Unfortunately, in a society bent on instant gratification and following one's impulsive desires, too many photographers pick up a camera, rush outside, and start shooting without regard to the elements nature is providing. The result, far more often than not, is totally inferior photography of under developed concepts. Again, to quote Adams, "There is nothing worse than a brilliant image of a fuzzy concept."

The challenge here is that sunlight is never going to be exactly the same from one day to the next. Atmospheric conditions, clouds, air temperature and the earth's natural rotation all factor into how sunlight illuminates a specific object in a specific position at a particular time of day. To observe light at 7:10 AM today is an insufficient indicator of where and how light falls at the same time next week. One must be part astronomer, part mathematician, and part meteorologist to accurately predict sunlight on any given day.

Fortunately, for most photographic work, one does not need exact measurements. There is generally a range of a few minutes that is reasonably acceptable for quality photography. Even then, however, one must be keenly aware of what changes occur as the sun moves across the sky. As the sun rises higher in the sky, the increasing temperature of the light (not the air) effects the reflective tone, while the angle and position of the sun effects the direction and intensity of shadows.

To illustrate, consider the following images of an antique ceramic wash basin and pitcher. The white ceramic does a wonderful job of reflecting the tonal temperature of the sunlight in the early morning.

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The three images, taken approximately thirty minutes apart, demonstrate a distinct change in tonality resulting from the increasing temperature of the sunlight. In the first image, taken at 7:21 AM EDT (-6:00 GMT), there is a distinct and recognizable amber hue reflected by the bowl and basin. The second image, taken thirty minutes later, still shows a hit of amber reflection, but one can see that the effect is considerably diminished from the earlier photograph. By the time of the third image, taken just over an hour from the first, there is only the slightest hint of amber left, the sunlight having changed considerably.

Which image is best? When is the better time to shoot?

The answer lies in defining the concept of the photograph. If the purpose is to accurately portray the colors of the bowl, then the third image is better. In fact, one might want to wait another fifteen to thirty minutes to completely remove any trace of amber reflection. However, if one's purpose is more artistic, leaning toward capturing the hue of an early spring morning, then perhaps the first image is more suitable to that end.

When working with people, often the earlier light is preferable, depending on the person's skin tone. Especially when working with individuals who have very fair, almost translucent skin, the amber tone of the early morning or late evening brings much needed color to the image and helps prevent over exposing some of the natural trouble spots. However, if the subject has been spending countless hours in the tanning bed getting ready for summer, the amber tone may cause the skin to reflect a ghastly orange, making a warmer light preferable.

The second factor one has to consider when shooting outdoors is shadow, not merely in terms of position, but intensity as well. Angle of the sun and of the camera in relation to the subject both play tremendous roles in determining where and how shadowing effects a photograph. Generally speaking, shadows are longer, and softer, when the sun is less than thirty degrees above the horizon. However, unless one is shooting in the middle of a desert or on an ocean beach, the sun is likely to be obscured by trees, buildings, and other obstacles that eliminate much of that period from exhibiting usable light. If the concept requires capturing the softest shadows, one may struggle to find a location with clear access to the horizon. Workable shadows may be present, depending on conditions, up to a 45 degree angle of the sun above horizon, but beyond that shadows become quite short and very harsh.

Just how quickly shadow changes is illustrated in the following set of images, converted to black and white to emphasize the shadow gradient.




Again, the most distinct difference is observed between the first image, taken at 7:22 AM EDT, and the last, taken at 8:20 AM. The red marks provide points of reference for marking noticeable changes in the location and spread of the shadows. One can see how with the time progression the shadows shorten and become more intense toward the back of the bowl, the side furthest from the sun. The gradient that is soft and gradual in the first two images, becomes much more hard and defined within a relatively short period of time.

Softer shadow gradients are generally preferable when one is photographing people. Long shadow gradients soften facial features and, in some cases, can even be useful in hiding problem areas. Short, intense gradients may cause a person to appear more stern, chiseled, and hard by comparison. Shorter gradients benefit architectural images, providing sharp definitions to lines and intricate features that might otherwise be missed.

Shooting outdoors is something of a paradox. One one hand, photographers need to know what manner of light is going to be best suited to the subject and schedule their work around the optimum time for achieving that light. At the same time, however, one can scarcely predict with accuracy whether the weather and other atmospheric conditions will actually provide the light desired. Spring weather can be surprising in how quickly it changes, requiring tremendous flexibility on the part of the photographer and anyone else involved. Certainly, there are those times when nature seems to hand one the perfect setting, just add camera and click. But the professional photographer knows knows that such luck comes partly from knowing what time of day nature is likely to deliver such an opportunity and having the skill to best take advantage of the gift.

Nonetheless, Spring offers one a delightful opportunity to break free of the constraints of artificial light, breathe a bit of fresh air, and enjoy the natural world. Setting one's alarm early and going out with camera in one hand and coffee in the other can be an exhilarating start to the day and create an opportunity for truly amazing images. There is a little of Ansel Adams in all of us. Take a moment in the sun and enjoy!

LIGHT BASICS :: ALL THOSE COLORS!

14 million colors. Sounds impressive, doesn't it? At least, it once did. When digital imaging crossed the threshold to achieve 14 million colors it seemed as though such a marvelous thing had been achieved. Yet, it is now possible to achieve color bit depths of 48 bits per pixel, theoretically giving one the ability to produce 281 TRILLION colors! Is such bit depth really necessary? How many colors can the human eye see, anyway? And what is the source of all these colors?

Color, of course, is how the human eye perceives various wavelengths of light. In elementary schools, we are introduced to the color wheel and told there are three primary colors: red, yellow, and blue. Shortly after getting that little fact in our head, though, confusion ensues. Digital cameras utilize a color space where green replaces yellow, and printers live and die by a Cyan, Magenta, Yellow and Black (K) color space. Which is correct? Why can't anyone agree?

First, we must consider how the human eye perceives color. Within the human retina sit three color-discriminating cones, commonly labeled L, M, and S for their peak sensitivities of long, medium, and short wavelengths. As light comes through the retina, the three cones work together adding and subtracting information to create three signals: Total Brightness, Red vs. Green (r/g), and Yellow vs. Blue (y/b). All the possible combinations of positive and negative r/g and y/b signals result in the discernible spectrum of just over 10 million colors.

Interestingly enough, many digital cameras attempt to duplicate how the three cones translate color through the use of what's called a Bayer filter pattern. No, there isn't an aspirin inside the camera. The Bayer filter alternates a row of red and green filters with yellow and blue filters in such a way as to mimic how the three cones address color. The filter outputs a mosaic image to which the camera's processor applies a demosaic algorithm. Better yet, higher quality camera actually use three different color processors, giving even greater color accuracy to the image.

The difference between the cones of the human eye and color filters in a digital camera is that the three cones cannot accurately be assigned a red, green, or blue label. Hues dramatically overlap on all three cones. However, it is important to realize that longer wavelengths produce more red-toned hues while shorter wavelengths produce blue tones, with green and yellow falling within various points of the midrange.

What one can accurately determine is the wavelength of light necessary to produce a given color. Just to be academically correct, I am obliged to mention that light can also be measured in terms of frequency and energy. For purposes related to photography, however, wavelength measured in nanometers is the more appropriate measurement.

red	700 nm
orange	620 nm
yellow	580 nm
green	530 nm
blue	470 nm
violet	420 nm

What causes changes in wavelength? In natural light, heat is the primary factor in determining light wavelengths. The hotter the light, the shorter the wavelength. Wavelengths can also be altered as light passes through a prism. Both have applications in photography.

When shooting in natural light, changes in light temperature as the sun rises and sets can dramatically effect the color accuracy of a photograph. If the camera is expecting light with longer wavelengths but receives shorter wavelengths, it inevitably mis-processes the information, resulting in inaccurate color. As the wavelength of sunlight changes constantly throughout the day, photographers must adjust how their cameras interpret color by re-setting their white balance or changing film types.

Light refraction comes into play most commonly through the lenses and filters one chooses for the camera. Because camera lenses are inherently curved, light is naturally refracted in a precise manner so as to send accurate information to whatever media awaits, whether film or digital CCD. Placing filters over the lens alters the refraction of the light, either shortening or lengthening the light wave for the purpose of making a color adjustment.

Here's where color gets a little confusing for photographers, so pay careful attention. When photographers speak of making an image "cooler," the effect is to warm the light by shortening the wavelength, most often achieved with a blue filter. To "warm" an image, one must cool the light, lengthening the wave by added either a red or amber filter. Since filters do not actually generate or reduce heat, however, they achieve the same effect through careful refraction. focusing on a specific gamut range. Cheap, inexpensive filters are often not as accurate in their refraction and fail to produce the desired results.

Many people can relate to the experience of shopping for clothes, picking out an item they think is a particular shade of red or blue or green, only to get outside the store and realize the garment's color is a very different hue from what one saw in the store! What happened? Did the garment magically change colors? Probably not (though some materials may give that illusion). What changes is the wavelength of the light in the viewing environment, effecting both color and brightness. Indoors, under fluorescent light, the wavelengths are more moderate, muting both reds and blues. In bright sunlight, wavelengths are shorter and brighter, emphasizing blues and violets, changing tonal perception.

For photographers, such changes in wavelength and brightness have huge implications for when and where one takes pictures. If an assignment calls for photographing items majoring within the blue hues, typically 550 nm or shorter, one is likely to achieve best success shooting outdoors of the morning, as the light temperature moves from cooler to warmer, favoring the blue- to violet-colored materials. Garments with yellow to red hues will photograph better in an evening sun, as the light grows cooler. Photographs taken in shade will inevitably favor blue and green hues but skew toward orange in the summer as longer days allow one to take advantage of more slowly cooling wavelengths.

Color theory can become incredibly complex and difficult to understand without a degree in physics. However, to the extent a photographer understands light and color one can make more intelligent decisions regarding lighting and settings for photographs. One of the best resources on the Internet is Professor Walter Lewin's lecture on Rainbows (lecture # 22) at M.I.T. His unique explanation and demonstration is one that I think most any serious photographer will find helpful.

LIGHT BASICS :: IS IT TOO HOT IN HERE?

Light.

The most basic, elemental form of energy, light is the most critical element for all forms of life. As photographers, we wrestle constantly with light, whether there is too little, too much, or coming from the wrong direction. Much of the anxiety can be eased by putting more effort to understanding this most fundamental element and its most critical role in creating the pictures we love.

Visible light, what the human eye is capable of seeing, is but a very small part of the eletromagnetic spectrum. The combined fluctuations of electric and magnetic waves transport energy from point A to point B. As light interacts with matter, the wave changes, allowing the human eye to assess the qualities of the matter. These changes in light are what our eyes interpret as color.

We measure light, and subsequently color, in terms of temperature. Without getting bogged down into scientific explanations, the amount of heat emitted from a light source determines its color (with the exception of fluorescent bulbs). These temperatures, measured most typically on what is called a black-body scale, are important in helping us determine what it absolute white. When shooting film, for example, tungsten film recognizes white according to the temperature of light emitted from a tungsten bulb, which is 2800 K. Daylight film, by contrast, recognizes pure white on a range between 5500-6000 K. Using film inappropriate to the light source inevitably alters how the film interprets color. Fluorescent light presents a challenge to photography because the light does not originate with a heat source and therefore varies in temperature, making it nearly impossible to find an accurate point for white balance.

What difference does any of this make?

Consider the challenges of outdoor photography. Experienced photographers will often talk about catching the "magic hour," within one hour after sunrise or one hour before sunset. The reason is because of the temperature of sunlight during those periods of time.

Look at the following outdoor temperature scale:

Sunlight: Sunrise or Sunset	2000
Sunlight: One hour after Sunrise	3500
Sunlight: Early morning or late afternoon	4300
AverageSummer Sunlight at Noon (mid-latitudes)	5400
Direct Mid-Summer sunlight	5800
Overcast	6000
Daylight Fluorescent Lamp (see note)	6300
Average summer sunlight	6500
Light summer shade	7100
Average summer shade	8000
Summer skylight	9500 - 30,000

NOTE: There are six different types of fluorescent lamps, making it virtually impossible to know what the exact white temperature is going to be. Even the best fluorescent filters tend to leave a greenish hue, making fluorescent light a challenge for photography.

If we assume that the professional tungsten lamp temperature of 3200 K is ideal for portrait photography, then once the sunlight temperature exceeds 3500 K, one can anticipate increasingly severe problems as the light temperature steadily climbs. Even overcast skies emit a temperature hot enough to skew color on outdoor film.

NOTE: Light temperature should not be confused with illumination. A 75-watt incandescent bulb has a light temperature of 2850 but hardly emits enough illumination for a quality photograph.

Of course, most people who pick up a camera now don't worry about film as they are using digital products that have auto-white balance settings. Given the abundance of digital cameras and white-balance settings, is light temperature still a factor to consider? Absolutely! Auto-white balance settings are rarely, if ever, accurate enough for professional work, especially if one places any type filter on the front of the lens. Even pre-loaded settings such as "shade" or "overcast" are not likely to be as reliable as professional work demands.
For example, a "shade" setting of 7000K might be appropriate for light shade in summer, but in heavy shade would result in a definite chromatic shift toward green and yellow.

Digital photographers generally have two options. One is to set a custom white-balance by taking a reference picture of a white card in the given light setting. This works in situations where the light source remains at a constant temperature. However, the reference photo quickly becomes obsolete when shooting outdoors. More appropriate may be setting the color temperature manually. Most Canon EOS DSLR and Nikon D series cameras have a manual range from 2300K to 10,000K, which pretty much covers all but the hottest of summer skylights.
However, such settings are useless if the person holding the camera doesn't know how to properly apply them!

In addition to the scale above, some temperature settings worth remembering are:

Match flame	1700
Candle flame	1850
Full Moonlight	4100
Electronic Flash	5500-6000
Xenon arc lamp	6420
TV Screen	9300

Granted, software tools such as Photoshop provide the digital photographer with multiple tools for correcting color issues caused by an incorrect white balance. However, relying on software is inefficient when faced with more than two or three images. Attempting to resolve white balance issues through batch processing delivers nothing short of mediocrity. A wise photographer solves light temperature issues on the camera, either through film choice or by adjusting digital light temperature settings.

Try it. The difference in the quality of one's photography grows the more one understands the elements going into a great picture.