Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Making a photo to take home

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.

 

Procedure


Using a pinhole camera

a 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. 
 
b 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. 
 A Photo

Image courtesy of Brenda Jennison 
 
Using a lens camera 
 
c 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


1 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! 

2 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. 
 
3 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-checked in January 2007