CS 39J > Schedule & Notes > Session 1 Detailed Notes

CS 39J: Session 1

http://inst.eecs.berkeley.edu/~cs39j/session01.html
24 January 2002

Prof. Barsky, in the Fujitsu Seminar Room, speaks about the CS 39J course.Introduction

A frequent question is, "What is a photography course doing in computer science?" It is simply because photography is my hobby and I happen to teach in the Computer Science Division.

This course will address topics that are photographic in nature, plus peripheral topics that photographers do not usually study. This is a freshman/sophomore seminar — therefore, we will have students discuss and interact and have everyone get to know each other. Students need some photography background — unfortunately, this is not a class for novices in photography.

Students will also be doing photography during the class. They need a camera with manual exposure control (not just a simple "point-and-shoot" camera).


Photographic Ethics and Questions to Ponder

One of the issues in photography is: "Is photography documenting reality, or providing interpretation?" What about documentary photography vs. posed photography?

One kind of photography is photojournalism — depicting reality and telling a story. But what if, for example, a photographer stages a photograph in Rwanda to convey a story about human rights abuses; is it truly photojournalism?

A more innocuous example would be taking a photograph at dusk but underexposing it to convey the impression of a night shot. It is not very serious but it is the case of the photographer intentionally manipulating the image to convey something different from reality.

We are at the crossroads in photography because of the advent of digital photography. It is now possible to make realistic images that are significantly digitally altered! One such computer program that allows us to do this is Adobe Photoshop.

If a photograph has technical flaws that are overcome by sophisticated use of a program such as Photoshop, do we consider the photographer as skilled or unskilled?


Preliminary Quiz

A "Preliminary Quiz" was handed out to determine the level of photographic knowledge of the students and then the questions and answers were discussed.


Aperture size and Controlling the Volume of Light for a Lens and the Eye

The aperture size controls how "wide open" the lens is, and this controls the depth of field (as discussed below). This is analogous to the pupil of the eye which is the hole formed by the iris. The pupil controls how much light gets into the eye.

Note that the pupil is secondary to the photoreceptors in the retina in the back of the eye in effectiveness to control sensitivity to varying light levels.

For example, when entering a dark environment, the process of "dark adaptation" occurs, comprising pupil dilation and increase in photoreceptor sensitivity.

The first phenomenon to occur, in a matter of seconds, is the dilation of the pupil. The average overall pupil range is about 2 mm to 8 mm, implying a factor of (8/2)2 = 16 between a small and large aperture. The maximum aperture depends on age, and would be about 5.5 mm for older people and might even be as much as 9 mm for some young people.

The second phenomenon relates to changing the sensitivity of the photoreceptors in the retina. In bright light, the rhodopsin in the rods is bleached by the bright light. When entering a dark environment, the retina regenerates the rhodopsin, requiring about an hour after strong bleaching. Rhodopsin is very sensitive to light and its presence in the rods increases the sensitivity by a factor of about 100,000. Compare that to the factor of 16 we computed above for the effectiveness of the pupil. A similar situation exists for the cones with the regeneration of erythrolab ("red" cones), chlorolab ("green" cones), and cyanolab ("blue" cones).


Depth of field

Depth of field refers to the range of distances in a scene that are in focus in the image; in other words, how much of the image can be kept in focus. The smaller the aperture is, the more depth of field there is; conversely, a larger aperture reduces the depth of field.

One might say, "Shouldn't I always have the aperture size set as small as posible, to get everything in focus?" Not always, since oftentimes using a larger aperture facilitates better control over blurring which can be desirable in the photographic composition (for example, blurring the background to make a subject stand out more).


Exposure control

An f/stop is a quantitative measure of the aperture size. We will explain this in more detail later in the course. Lower f/stop numbers indicate wider aperture sizes.

The shutter speed controls the exposure time, that is, for how much time we are allowing light to enter the lens and expose the film (or the CCD array in the case of a digital camera).

Using a tripod allows reduces "camera-shake". Even if a tripod is not available, it is a good idea to try to rest the camera on a solid surface when taking photographs.


Film speed

The degree of sensitivity of a film to light is referred to as the "film speed". More sensitive films are said to be "faster" and, conversely, less sensitive films are referred to as "slower". The speed is quanitified by an ISO number. ISO is the abbreviation for the International Standards Organization. However, photographers usually refer to this as the ASA, an historical reference to what used to be called the American Standards Association which was formed in 1928 after a reorganization of the American National Standards Committee. ASA changed its name in 1966 to the American National Standards Institute (ANSI).

Another standard is called DIN, which is the abbreviation for the Deutsche Industrie Norm, a German standards organization. The disadvantage of the "faster" films is that they are more grainy. We will discuss the reasons for this later in the course.


California photographic tradition

California has a rich history in photography, with famous photographers such as Ansel Adams, Edward Weston, Willard Van Dyke, and Imogen Cunningham. They called themselves the f/64 Group, which was organized in 1932. The name was chosen because f/64 is the smallest aperture one usually finds on the lens of a large-format camera and would thus provide the most depth of field. They formed the group in response to the artistic, soft-focus type of photography which was popular at the time. The philosophy of the group was to have "pure" photography comprising sharp images, maximum depth-of-field
and smooth glossy printing paper. The "Group f/64 Manifesto" is shown below:


Group f/64 Manifesto

The name of this Group is derived from a diaphragm number of the photographic lens. It signifies to a large extent the qualities of clearness and definition of the photographic image which is an important element in the work of members of this Group.

The chief object of the Group is to present in frequent shows what it considers the best contemporary photography of the West; in addition to the showing of the work of its members, it will include prints from other photographers who evidence tendencies in their work similar to that of the Group.

Group f/64 is not pretending to cover the entire of photography or to indicate through its selection of members any deprecating opinion of the photographers who are not included in its shows. There are great number of serious workers in photography whose style and technique does not relate to the metier of the Group.

Group f/64 limits its members and invitational names to those workers who are striving to define photography as an art form by simple and direct presentation through purely photographic methods. The Group will show no work at any time that does not conform to its standards of pure photography. Pure photography is defined as possessing no qualities of technique, composition or idea, derivative of any other art form. The production of the "Pictorialist," on the other hand, indicates a devotion to principles of art which are directly related to painting and the graphic arts.

The members of Group f/64 believe that photography, as an art form, must develop along lines defined by the actualities and limitations of the photographic medium, and must always remain independent of ideological conventions of art and aesthetics that are reminiscent of a period and culture antedating the growth of the medium itself.

The Group will appreciate information regarding any serious work in photography that has escaped its attention, and is favorable towards establishing itself as a Forum of Modern Photography.

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CS 39J: The Art and Science of Photography is a freshman seminar taught by Professor Brian A. Barsky.
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