how a camera works & pinhole photography… yippeee!!!

How a Camera works & Pinhole Photography…

Yippeee!!!

Aperture

Focal Point / Plane

Circles of Confusion

When the circles of confusion are small enough they are called “points” and the optical image is considered to be in focus.

An optical image entering the lens is made up of very

“tiny circles of confusion.”

Thus… points of focus or “Focal Point (Plane)”

Focal Plane or Focal Pointwhere the image is in focus.

•This is depth of field.

•The lens focuses the image on the focal plane.

•Any movement of the lens or the film forward or backward increases the size of the circles of confusion and takes the image out of focus.

•When the aperture is stopped down, the resulting circles of confusion that are in the front and the back of the focal plane become smaller and smaller and are regarded by the human eye as being more like points of focus.

A pinhole camera has infinite depth of field because the pinhole creates circles of

confusion more or less the same as the pinhole all over the inside of the camera, and

the circles of confusion are small enough to be regarded as point of focus.

That means the photograph has a high enough resolution (resolving the points of

focus) to be acceptable as a coherent image.

Film (Focal Plane where the image is in focus.)

LightEmulsion SensitivityASA/ISO

ApertureInterval of Light /

Shutter Speed

Exposure is how much light hits your film.

Exposure is controlled by FOUR factors.

•If something has a light sensitive emulsion then the more light you expose it to, the more it will be

affected.

•How much and what kind of light you use helps determine exposure.

Because….

A high number is faster than a slow number and therefore reacts more quickly to the light.

•Film speed is measured in ISO or ASAThe ISO is the International Standards OrganizationNot to be outdone, we have the ASA or the American

Standards Organization (which has now been renamed the American National Standards Institute or ANSI)

Some examples are…

50, 100, 125, 200, 400, 800, 1600, 3200, 6400

The formula for determining film speed is long, involved and highly mathematical. Therefore, we won’t go in to it except to say...

Conveniently, ISO numbers and ASA numbers are, for the most part, the same.

•Aperture is how big lens opening is.

3.5 4 5.6 8 11 16

•The measurement is determined by the angle of the shutters covering the rest of the whole.

•Each stop cuts the amount of light in half.

How long the hole (shutter) is open.

Some Sample Shutter Speeds:

1, 2, 4, 8, 16, 32, 125, 250, 500, 1000, 2000

This and all the other concepts that we have discussed today will be explored further. But for now, let’s talk a little about the history of photography…

Principles of photography first discussed by a Chinese philosopher, Mo Ti or Mo Tzu who lived in the 5th century BC. And further discussed by Aristotle in the century following.

Camera Obscura (Dark Room)

The first discussion of something resembling a camera obscura was by a Persian (Iraqi) Abu Ali Al-Hasan who lived in the 10th Century.

Used initially only by scientists, the camera obscura was used by artists such as Leonardo da Vinci as early as the 15th Century.

A precursor to movies, camera obscuras were used as an early form of entertainment.

It wasn’t until 200 years after the camera obscura was first developed that the chemical developments necessary for contemporary photography were discovered.

It was these same philosophers an scientists Mo Ti, Aristotle and Ali al-Hasan who first discussed the concept of the pinhole camera and it’s usefulness as an aide in viewing the sun and eclipses.

By the 1800s, pinholes were being used in a variety of way to actually take photographic images.

The ease of the pinhole camera is that it can be made from just about any light-safe box.

Clarissa Carnel, Stonehenge 5x7 1986

Marianne Engberg, Greenland series 7” diameter pinhole 1980

Peter Olpe, Lago Massiore, North Italy 5x8 1978

Jeff Spirer, Chamber 2000

Dona McAdams, Brooklyn Bridge 8x10 1983

Eva Westerland, Tightrope from Solitary Traveler series 81/2 x61/4 1999

Julie Schacter, Ronald Reagan 4x5 with Boraxo Camera 1980s

Marcus Kaiser, camera in Berlin Wall 1990

Jochen Dietrich, Self Portrait 3.5x3.5 from Clock Camera 1993

Jeff Fletcher, Bromide EggsEggshell coated with “liquid light”, then placed inside pepper shaker, each image is made with one pinhole lens, photograph of 18 pinhole images 1989

Paolo Gioli, Self Portrait 4x5 1972

Jurgen Konigs, Sieb 4.5x9 1990

Nancy Spencer, 11/2”, 3” 6”

Eric Renner, Ticul Schoolyard 1969

Ian Paterson, Luxembourg Gardens (Paris) 5x7 1989

Willie Anne Wright, Sleeping Confederates from the reenactment of the battle of Chacelorsville 8.5x6.5 1988

Jim Haberman, Marjoire 4.5x4.5 1976

Ruth Thorne-Thomsen, Expeditions, Chicago 4x5 1979

Walter Crump, Scribe (Islamabad Pakistan) 10x10 Bleached & Toned 1992

Mark Dungan, Sphinx Joseph 4x5 1999

Jessica Ferguson, In My Studio (Self/Pig Skull/Rabbit) 8x10 1993

Fin