How Photography Works Friday, August 27

SWBAT explain the permanent formation of an image How photography works

How Photography Works Photography has to do with light forming an image, normally by means of a lens. This image is then permanently recorded either by: – Chemical means, using film, liquid chemicals and darkroom processes. – Digital means, using an electronic sensor, data storage and processing, and print-out via a computer.

Image Formation Chemical forms of image recording have steadily improved since the middle of the nineteenth century. Digital methods have only become practical within the past five years but are rapidly evolving. Photographers increasingly combine the two – shooting on film and then transferring results into digital form for manipulating and print- put.

Forming and Exposing an Image Light from the subject of your picture passes through a glass lens, which bends it into a focused (normally miniature) image. The lens is at the front of a camera with a light sensitive surface such as film facing it. Light is prevented from reaching the film by a shutter until your chosen moment of exposure.

Forming and exposing an image The amount of exposure to light is most often controlled by a combination of the time the shutter is open and the diameter of the light beam passing through the lens. Shutter time alters the way movement is recorded - blurred or frozen.

The Chemical Route Processing – If you use a film camera, the next stage will be to process your film. – First, film developing chemicals are applied to the film in complete darkness. If additional light hits your film, your images will be ruined. – Second, another type of chemical dissolves or “fixes” away the unexposed parts of the film.

The Chemical Route Printing Negatives – The next stage of production is printing, or enlarging. – Your film is set up on a vertical projector called an Enlarger. The Enlarger lens forms an image on to light sensitive photo paper. – Next, your photo paper is processed in yet another chemical solution

The Digital Route Storing, Downloading and Processing – If you are using a digital camera the exposed image is recorded on a grid of millions of microscopic size light sensitive elements. This is known as a CCD, or Charge Coupled Device. – Immediately following exposure the CCD reads out its captured picture as a chain of electronic signals called an image file, usually onto a small memory card slotted into the camera. – These image files are later downloaded from the card into a computer and printed using a desktop printer