Picture This: Highlights and Shadows
Exposure controls help preserve details in a photograph’s lightest and darkest areas.
By Earl Nottingham
The human eye is truly a remarkable instrument. Its abilities to distinguish billions of color variations and adapt to extreme brightness or darkness far surpass the most advanced camera sensor or film emulsion. Even at its best, a photograph is only a condensed approximation of the wide range of color and brightness that we are capable of seeing. For the most part we deem the final photograph an acceptable representation of the scene we saw.
Many times, however, because of the limitations of sensors and films in recording a full range of detail in extremely bright objects such as white clouds or in dark shadowed objects, we are disappointed that the final photograph did not do justice to the scene we thought we were recording. While our eye can easily distinguish the gentle variations of tonality in the whites of the clouds as well as details in darkest shadowed areas, our photograph may render the clouds as solid white and the shadows as pure black.
We use the terms “blown out” or “clipped” to indicate extreme whites or blacks where textural detail has been lost because of overexposure in the lighter areas or underexposure in darker areas.
Slight variations in exposure can make or break a great photo. In the photo above, the camera’s automatic exposure has blown out the detail in the lighter clouds. In the photo below, by manually lowering the exposure slightly, the delicate tonal differences have become apparent, giving the photo a greater sense of realism and depth.
In a best-case scenario, any given scene would have a range of luminosity that fits within the camera’s ability to record the scene’s full range of tones. In practice, this type of lighting exists mainly in lower-contrast lighting situations such as a cloudy day or slightly diffused sunlit day or at the “magic light” times of day such as early morning or late evening.
In the absence of such made-to-order lighting, we can modify existing high-contrast lighting by either adding a reflector to the shadow side of a subject (especially portraits) or by blocking a brightly lit area with various types of translucent or opaque materials. For close-up scenes of people or objects in high-contrast light, the camera’s built-in flash can be used to gently fill in shadows (fill flash). Either way, the objective is to ensure a contrast level that is aesthetically pleasing as well as within the sensor’s range to accurately reproduce a full range of tones.
To aid the photographer in determining whether or not a highlight portion of an image will be overexposed (blown out), most cameras provide some type of highlight warning, usually in the form of a flashing crosshatched pattern called a “zebra” or a bright-colored overlay on the LCD screen as the image is reviewed.
These features may need to be enabled in your camera’s setup menu in order to be seen. A flashing highlight warning indicates that you must lower the overall exposure with either manual settings or with the exposure compensation feature. Typically, you will see the warnings when shooting clouds or light-toned clothing.
Alternately, the camera’s histogram is a useful tool that provides a simple graphic representation of the range of tones from pure black to pure white in a given image. As long as the graph is constrained within the left and right boundaries of the histogram, you will have detail from the darkest to the lightest areas of the image. I find it is much easier to use the histogram as a reference for proper exposure than to look at the photograph displayed on the LCD screen, especially when viewing the screen in extremely bright or dark environments.
To see how your camera deals with the higher exposure, shoot a scene that contains some light-toned or white objects to see if those tones are being reproduced without being blown out — or whether some plus or minus exposure compensation is needed to find the sweet spot where the first indication of texture appears. Some cameras tend to consistently either overexpose or underexpose images and can be adjusted with the exposure compensation feature.
Also, digital cameras will yield a wider range of tones if a picture style (from the setup menu) such as “Neutral” or “Natural” is used. Although picture styles such as “Vivid,” “Standard” and “Landscape” yield brighter colors, they tend to have stronger contrast, and highlights are easily blown out. Watch your highlight warning feature with these picture styles and lower your exposure as needed.
The preservation of delicate textural detail in both highlights and important shadow areas through proper exposure control gives a photograph a sense of reality and presence and rewards us with a three-dimensional feel in a two-dimensional medium.
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