Luminosity is represented in a photograph by tones of black, white and gray. Luminosity is light. It represents all that we can see about the world we photograph. Every object, event and mood depends upon visible light represented by luminosity in the photograph.

Luminosity is important to visualize when we’re taking a picture, transforming it in Photoshop, calibrating our monitor and printing. Because of the nature of visual perception, hue and saturation are processed separately from luminosity in our brains, and we must forcibly separate luminosity and train ourselves to see it to accomplish the quality we desire in a digital fine print. A good print starts with seeing the luminosity of a scene and ends with it.

Photographing Light
The photograph of the Matterhorn was made with a Kodak Instamatic camera in 1964 when I was 19 years old. This photograph has been one of my greatest teachers. I’ve kept it by my bedside for years and I’ve learned more about photography and the world from it than from all the hundreds of books or teachers or photographs I’ve known. It’s largely important because I made it before I knew anything at all about photography or ƒ-stops or film speeds or great photographers. It’s pristine vision. The camera was the cheapest Instamatic Kodak made (about $10, if I remember correctly). The film came in a cartridge that you dropped in, and the image size was one inch by one inch.

I knew at the instant I snapped the shutter that the photograph was a good one, at least visually. I’ve spent more than four decades trying to figure out why, and I’ve learned much. One of the most important things I’ve learned is about light and how to photograph it. That morning, looking at the Matterhorn, I discovered luminosity.

The light in this photograph has always been special to me, and I continually want to know why. The light seems to be a part of the scene and yet not part of it. How do we see this, and how do we, metaphorically, put ourselves in the path of its beam? The answer, for me, came from the aesthetic interpretation of two concepts that describe light: ambient light and reflected light.

Ambient light is the light from a light source (in this case, the sun) that falls upon the subject we’re photographing. Reflected light is the light reflected from the subject we’re photographing (in this case, the Matterhorn). The quality of both types of light is seen and represented differently in the black-and-white luminous tones of a photograph. Here’s what two great men have written about this peculiar phenomenon.

ABOVE: Luminosity as displayed through images 1 to 3. Figure 1 is the original scene as shown in color. Figure 2 reveals the same image as seen with the 90 viewing filter with most of the color subtracted. This monotone view helps to uncover the possibilities of the luminosity present within the image. Figure 3 is the final photograph as seen when converted into black-and-white.

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Dr. Edwin Land, from the 1978 Polaroid annual report:

“…the photograph is two entirely different kinds of report transmitted to us by what appear to be mixed languages, the language for delineating objects and the language for displaying illumination.

“There haven’t been many great photographers in history, but the great ones usually turn out to be masters of the vocabulary of these two utterly different languages in black and white photography. For most would-be photographers these languages are mixed together and never disentangle, like the babble of voices at a cocktail party. The breathtaking competence of the great photographer is to cause the object of his choice to be revealed with symphonic grandeur, meticulous in detail, majestic in illumination.”

Ansel Adams, from Natural Light Photography (1952): “Light, to the accomplished photographer, is as much an actuality as is substance such as rock and flesh; it is an element to be evaluated and interpreted. The impression of light and the impression of substance which are achieved through the careful use of light are equally essential to the realistic photographic image…To utilize it (natural outdoor light) fully you must know how to evaluate its intensities and qualities, not only in their effect on sensitive emulsions, but also in relation to the intangible elements of insight and emotion that are expressed in a good photograph. A certain esthetic philosophy is involved; something more than the physical conditions of light and exposure…the chief problem is to preserve the illusion of light falling upon the subject. A print intended to convey an emotional impression might differ from a normal photographic record.”

Both Land and Adams are talking here about the same thing. They’re talking in general terms about the two types of light that a photographer has to deal with: the light reflecting from a subject (reflected light) that causes its texture and form and the light falling on the subject (ambient light) that causes the overall “mood” or aesthetic character of the image. The quality of light both reflected from the object and the ambient illumination falling on the entire scene are represented in the photographic print by luminosity alone.

Visualizing Luminosity
Taking time to visualize and control the luminosity in a photograph will pay rich rewards in the print. The first tool that I use for this purpose is an item borrowed from traditional photography that helped photographers visualize a scene in black-and-white before taking the picture: a Kodak Wratten 90 monochromatic viewing filter.

The Tiffen #1 B&W Viewing filter is essentially the same filter, just in a fancier (and handier) viewer. The filter itself is amber, but it cancels out color and turns the world into a monochromatic view that shows the contrast relationships and tonal mergers that will occur in black-and-white photo-graphs. This filter also is used extensively in the motion-picture industry for the same purpose.

The 90 helps us to see a world that we have trouble visualizing. It’s available in many forms, from the original Kodak gel to the specially made viewers by Tiffen.

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When I study the scene in front of me for luminosity using this filter, if I like what I see through it, all I have to do in Photoshop is draw the saturation slider in Adobe Camera Raw to -100 (which desaturates the image and shows only the luminosity; in Photoshop CS3 and Lightroom, I simply press the Grayscale button). Doing this, I’ll usually achieve a decent black-and-white (luminosity) image right off the bat.

After getting a good luminosity image (by further refinement in Camera Raw or Lightroom, if necessary), I either keep it that way for a black-and-white print or convert it back to color. With this simple tool and correction, we see that luminosity is the key to controlling many important things in the image: color, shadow detail, highlight detail, midtone separation and tonal blending.

In the examples, you can see the original color scene, the image with the 90 viewing filter and the final photograph converted to black-and-white. The viewing filter subtracts most of the color from the image and we view it in monotone, helping us to see the possibilities of the luminosity.

Seeing And Controlling Luminosity In Photoshop.
While it’s relatively easy to see the reflected light from the surfaces of objects and control them with local burning and dodging in Lightroom and Photoshop, ambient light is quite another matter. As hinted by the quotes from Adams and Land, both are important for the “presence” of a good photograph and print, in color and black-and-white.

The struggle to find a method to reveal ambient light started for me more than 10 years ago. Through the work of Adams and realistic painters, I discovered that there exists in each photograph a web of light that represents the ambient “glue” that holds the feeling of the image together and allows it to unify. In reality, it’s a web of light that creates wholeness to the image.

Photoshop has an effective tool to identify and modify this “web of light” in a photograph: Color Range under the Select Menu. To find this web in an image, I open Color Range and look at the Highlights, Midtones and Shadows as separate areas. The one that has a web of light that covers most of the image (it could be in one or all three areas) is then chosen using the Color Range command, which turns that area into a selection that can be manipulated with Curves or Levels or other tools.

A photograph usually contains both ambient and reflected light, but one will usually dominate the other. Think of reflected light as defining an object and ambient light as a feeling. Absolutely defining such aesthetic truths is impossible. By engaging ourselves in this discovery process, we see that luminosity has meaning. There’s a visual vocabulary of tonal value caused by luminosity in black-and-white and color images that’s created by the action of light alone, independent of content. The answers to any questions about luminosity must be treated as a continually unsolved riddle that always changes and offers us endless possibilities for an authentic response of expression in a photograph.

To see more of George DeWolfe‘s work, visit www.georgedewolfe.com.