Formation of Images
Light, Sound and Waves

Making a photo to take home

Practical Activity for 14-16 PRACTICAL PHYISCS

Class practical

Producing a permanent photographic image.

Apparatus and Materials

  • Red or orange safelights
  • Floodlamp (preferably with photoflood bulb)
  • For each student or pair of students...
  • Pinhole camera
  • Black paper
  • Pin
  • Lens (+7D or 150 mm focal length)
  • Bromide paper, many pieces
  • Paper clips or hair clips, 2
  • Goggles
  • For every 8 cameras...
  • Photographic dishes (for developer and hypo), 2
  • Dish of water (or sink)
  • Developer
  • Hypo or fixer
  • Large tank or sink for washing
  • Newspaper or blotter to dry prints
  • Tongs

Health & Safety and Technical Notes

Eye protection (goggles) must be worn for this activity, as the developer is significantly alkaline. The paper must be handled with plastic tongs. Anyone with sensitive skin should wear gloves.

Read our standard health & safety guidance


Procedure

    Using a pinhole camera
  1. In a darkened room, load the camera with a piece of normal bromide paper, clipped on the inside of the back window. It is essential to obscure the translucent window at the back of the camera box with opaque paper or metal, otherwise stray light will enter though the window and fog the picture. Make a pinhole and enlarge it with a pencil point to 1 or 2 mm diameter. Cover the pinhole with a finger. Rest the camera on a table and point it at the head and shoulders of a 'subject' sitting about 2 metres away. Direct a bright floodlamp at the subject, and switch it on for 30 seconds or longer with the pinhole open.
  2. Remove the bromide paper, soak it in developer; watch it and wash it when you see the picture; dip it in hypo; give it a long wash, if possible in a sink with running water. The print can be (partially) dried on newspaper. When fully dry, it is ready to take home.
  3. Image courtesy of Brenda Jennison
  4. Using a lens camera
  5. Follow the same procedure as above with a fresh piece of bromide paper, but make a hole in the camera's front with a finger. Hold the lens against the hole. (You could use Sellotape.) Turn on the floodlamp and uncover the lens for one or two tenths of a second.

Teaching Notes

  • If possible, each student should have their own camera; or at most work in pairs. Anyone who has seen his or her first photographic print emerge in a developing dish will never forget it. But, be warned: get students to write their name on the back of the paper because the best photograph will belong to all of them!
  • A darkroom is not necessary if photographic paper is being used (though the image will be a negative). Sheet film can also be used, but a dark room will be needed, or skill with a film-changing bag. For those who understand f-numbers, you can draw up a table of apertures and exposure times for a given film speed. Superb photographic displays can be produced from this simple camera.
  • The camera obscura, a relative of the pinhole camera, has a long history of use in the art world and as a curiosity showing the surrounding landscape.

This experiment was safety-tested in January 2007

Formation of Images
can be represented by Ray Diagrams
is used in analyses relating to Lens
has the special case Real Image Virtual Image
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