Science for the Curious Photographer

An Introduction to the Science of Photography

Charles Johnson, Jr.

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781351811859
• Edition: 2
• Topic: Kunst
• Subtopic: Techniken der Fotografie

While there are many books that teach the "how-to" of photography, Science for the Curious Photographer is a book for those who also want to understand how photography works. Beginning with an introduction to the history and science of photography, Charles S. Johnson, Jr. addresses questions about the principles of photography, such as why a camera needs a lens, how lenses work, and why modern lenses are so complicated.

Addressing the complex aspects of digital photography, the book discusses color management, resolution, "noise" in images, and the limits of human perception. The creation and appreciation of art in photography is discussed from the standpoint of modern cognitive science.

A crucial read for those seeking the scientific context to photographic practice, this second edition has been comprehensively updated, including discussion of DSLRs, mirror-less cameras, and a new chapter on the limits of human vision and perception.

CHAPTER 1
What Is Photography?

 

 

 

The painter constructs, the photographer discloses.

—SUSAN SONTAG

You don’t take a photograph, you make it.

—ANSEL ADAMS

There are two sides to photography. First, photography is the capture and display of images by means of film or an electronic sensor; and, second, photography is the art of taking and presenting photographs. As commonly practiced, photography is inseparable from cameras. Of course, photography means “writing with light” and writing is really the operative word. When photography was discovered in 1839, the thing that was discovered was the means for permanently capturing images. Cameras of various kinds had, in fact, been available for centuries.

The original camera, known as the camera obscura (see Figure 1.1), was nothing more than a dark room with a small hole (aperture) in one wall and an inverted image on the opposite wall created by light rays passing through the aperture. The wonderful image forming property of a small aperture was noted by the philosophers Mo-Ti in China and Aristotle in Greece in the 5th and 4th centuries BCE, respectively, although apparently without an understanding of how it was accomplished. It is clear that scientists in the Western world from at least the time of Leonardo da Vinci (c. 1490) were aware of the camera obscura, and at some point it was discovered that the image quality and intensity could be improved by enlarging the aperture and inserting a convex lens of the appropriate focal length. The portable camera obscura, a box with a lens on one side and some means of viewing the image, became popular with artists as an aid in representing perspective in paintings. For example, the 16th-century Dutch painter Johannes Vermeer (1632–1675) almost certainly used a camera obscura to see the correct representation of perspective for his paintings. By the 19th century these devices were essentially box cameras without photographic film.

In the early 19th century many individuals were experimenting with sensitized materials that would darken when exposed to light to produce fleeting images, so proper credit for the invention of photography is diffuse and controversial. Probably the first permanent image from nature was obtained by Nicéphore Niépce in 1926/1927 with an 8 hour exposure on bitumen-coated pewter. However, photography, as we know it, dates from 1839, when two men independently reported processes for capturing images in the camera obscura. Their disclosures initiated explosive developments in image making around the world. A Frenchman, Louis Mandé Daguerre, discovered a method for producing a permanent image on a silver surface; while, in England, Henry Fox Talbot created permanent images on paper treated with a mixture containing silver chloride. In Daguerre’s images, the areas exposed to light and properly processed were highly reflecting; and, therefore, there was a natural (positive) appearance, though, of course, without color (monochrome). These images, which were called daguerrotypes, unfortunately could not easily be reproduced. However, the striking images obtained by Daguerre were an instant hit, and most contemporaries considered him to be the inventor of photography. (See Figure 1.2.)

FIGURE 1.1The camera obscura was used by Reinerus Gemma-Frisius in 1544 to observe an eclipse of the sun.

FIGURE 1.2 Louis Mandé Daguerre (left) and Henry Fox Talbot (right).

In marked contrast, Talbot’s images were initially unpleasing because the (bright) exposed areas were found to be dark on the paper. In other words, a negative image was produced. However, that turned out to be a great advantage because the negative could be combined with another sheet of sensitized paper and exposed to light to produce a positive copy, and that procedure could be repeated to produce multiple copies. Of course, paper is translucent rather than transparent, and it was not until the 1850s that transparent negatives could be obtained.

Apparently, the astronomer Johann Heinrich von Madler coined the term photography in 1839 when he combined the Greek words for “light” and “to write.” However, the terms photography and photograph are usually attributed to Sir John Herschel, who included them in a paper that he read to the Royal Society of London in 1839. Herschel deserves credit for advancing photographic science by discovering how to stabilize silver images. The term photography may actually have been introduced earlier by an artist named Hercules Florence working in Brazil in 1833. Florence, who used sensitized paper to copy drawings, did not report his work, and, as a consequence, he had little influence on the development of photography.

For the next 160 years, silver sensitized paper and film coupled with the negative/positive process dominated photography, and it was only after the year 2000 that photoelectric sensors and powerful, yet inexpensive, computers challenged film-based photography. Replacing film with sensors and computer memory has not yet basically changed photography; however, computer manipulation of images has turned out to be a revolutionary development. Even the few images still captured on film are now routinely scanned into computers and digitized so that they are also subject to modification and easy reproduction and printing. If computer image manipulations were limited to the types of things that photographers were already doing in the darkroom to correct exposure, hold back or burn in areas, change contrast, etc., there would be no fundamental change in photography. But now the changes can be so extensive and subtle that the boundaries of photography are continuously being tested.

It has been said that photographers reveal, while artists create. Software for manipulating photographic images and even creating realistic images from scratch is fundamentally changing this equation. Illustrators, using computer graphics, have almost unlimited ability to produce realistic images of any type. Photojournalists, on the other hand, must have their creative inclinations severely limited by a code of professional ethics and perhaps by authentication software that can spot even microscopic changes in digital images.

Anyone who has viewed recent movies knows that amazing things can be done to produce realistic images of things that never existed. The opening scenes in The Day After Tomorrow show a flight over ocean, ice, and cliffs in Antarctica. It is beautiful and impressive. How was it done? A helicopter flight over those remote areas would be costly and dangerous, so the producer decided to create the scenes entirely with computer graphics. And what about the magnificent scenes in the epic Troy? Does anyone believe that 1000 or even 100 ships were constructed, or that 75,000 Greek warriors took part in the battle? Computer-generated imagery (CGI) has certainly come of age as we can enjoy 3D spectacles such as the movie The Life of Pi, mostly created by Rhythm & Hues Studios, and wonder which scenes were actually photographed in nature. We may enjoy the endless possibilities for image making, but we can no longer (if ever we did) believe in what the images show.

So, ultimately, what is photography? Does it matter that wrinkles can be removed from faces and heads can even be switched? Do we care if it is easy to move an alligator from a zoo to a natural area or a hummingbird from a feeder to a flower? Some gullible observers may still marvel at how such “difficult” photographs could be obtained. We are seeing the emergence of a new art form, but I am not sure where that leaves photography. Will “pure” photography remain when everyone has an incentive to improve the images they obtain and it is so easy to do even in camera? Is there any merit in maintaining photography with minimum manipulation for recording the world as it is? The future will tell. In fact, “truth” is found in some novels and paintings and in some photographs, but it must be tested and verified by wise readers and observers.

Questions raised by the concepts of reality and truth in visual images are much more complex than may be thought. Later in the book I discuss the operation of the human visual system and its relation to our awareness of the world. It is fair to say that our eyes and brain create the illusion of a full-color, three-dimensional world. It is an illusion because the images projected on the retinas of our eyes do not provide enough information for the construction of a unique world view. The brain fills in details based on a sort of automatic inference system that is influenced by both the evolution of the human brain and the experience of the individual. The result is that we see, at first glance, pretty much what we expect to see. One should also realize that digital cameras basically compute pictures from captured light. The computation is not straightforward, and there is a lot of room for “enhancement” of the final image. The new field of computational photography is influencing the images produced by our cameras and the special effects we see in movies. It is an interesting time to be alive and maybe a little disturbing as well.

Futher Reading

Peres, M. R., Editor (2007). FOCAL Encyclopedia of Photography. Amsterdam: Elsevier. An extensive coverage of theory, applications, and science, but uneven and already dated.

Rosenblum, N. (1997). A World History of Photography, 3rd Ed. New York: Abbeville Press. A tour of photography from 1839 through the film era, including both art and the technical details.

CHAPTER 2
What Is Light?

All the fifty years of conscious brooding have brought me no closer to the answer to the question, “What are light quanta?” Of course today every rascal thinks he knows the answer, but he is deluding himself.

—ALBERT EINSTEIN, 1951

I therefore take the liberty of proposing for this hypothetical new atom, which … plays an essential part in every process of radiation the name photon.

—G.N. LEWIS IN NATURE, DECEMBER 18, 1926

We can wax eloquent: Light is universally revered. It represents illumination and understanding. It represents our greatest treasure, as in the “light of our lives.” We believe that bad things happen under cover of darkness, and evil works cannot stand the light of day. Light sets the pattern of our days. When light goes away, we sleep. Photography involves writing with light, and it uses the information in light to capture moments in our lives so that they are preserved and can be replayed. In this way, photography brings light to our past.

But here we need useful rather than poetic definitions that can help us understand photography. We all know the difference between light and dark, but what is light? The problem is that most definitions introduce other words that need to be defined. I will start with several ideas that are correct but not complete as a step toward understanding what we mean by light. First, light is a form of energy that comes to us from some source and can make our environment visible to us. Of course, even with our eyes closed we can tell the difference between bright light and no light. Another useful statement is that light is a kind of radiation that is visible to us. Again this implies energy, the ability to do work and affect change.

All of our energy, other than that associated with radioactivity, comes to us directly or indirectly from the sun, and the sun is our major source of light. The sun provides bright “white” light in the middle of the day and less intense yellow and red shades in the early morning and late afternoon, at least as seen from the surface of the earth (Figure 2.1). This sentence brings up the concepts of intensity and color, both of which are related to human perceptions. Therefore, the study of light in photography requires not only precise mathematical definitions of brightness and color, but also methods of quantify...