Question 4
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(a) Describe the photographic film.
(b) Mention two chemicals required for processing film.
(c) Identify seven equipment required for film processing.
Observation
Few candidates attempted this question and most of them responded unsatisfactorily. Some of the candidates could not identify the equipment required for film processing and this made them to lose significant marks. They were expected to respond with some of the following points:
(a) - Film is light sensitive and has chemical composition
- Black and white film is made up of grains of silver halides while colour films are from colour dyes using three layers of emulsion red, blue and green.
- Films are rated according to their speeds using internationally acceptable standards, e.g. ASA/ISO 100, ASA/ISO 200, ISO/ASA 400 etc.
- Films are manufactured for specific light sources, :daylight or indoor (tungsten) photography
- Photographic films are in formats, e.g. 110mm, 135mm, 120/220mm, 4 x 5 sheet.
- Some Colour and black & white films can be processed into positive reversals called transparencies/slides
(b) - Developer
- Fixer or fixing salt or Hypo
- Stop bath
- Wetting agent
(c) - Bottles
- Funnels
- Timer
- Thermometer
- Developing tanks/ Multi-reel tanks
- Tray
- Film hangers of film clip
- Film reel/spiral spool
- Beaker/ Mixing jug/ Graduates
- Film squeegee tongs
- Film wiper
- Stirring rod/ Agitating rod
- Scissors
- Drying Cabinet/ Dryer