Week 3

Exposure
total amount of light used to create an image
controlled by shutter speed and lens aperture
1/125sec at f2.8 same amount of exposure as
1000,500,250,125,69,30,15,8,4,2,1 shutter speed (length of exposure)
1,1.4,2, 2.8,4,5.6,8,11,16,22,32 f-number (intensity of exposure)
ISO rating
Subject lighting (level of reflectance)
Your preference
ISO rating
Film with high sensitivity to light has a high rating
Higher the number= greater the light
Film with low sensitivity to light has a lower rating
DIN (Deutches Institut Fur Normung)
ASA (American Standards Association)
ISO (International Standards Organisation)
Eg: Liford HP5> DIN27>ASA 400
Kodak Tmax100> DIN21>ASA 100
Agfrapan25> DIN15>ASA 25
1987: adoption of ISO as standard which uses ASA scale
ISO Standard
A double of the rating= doubling of sensitivity
Eg: ISO400 film is twice as sensitive to light as ISO200 film
Therefore: ISO400 film requires half the exposure as ISO200 film to produce a specific exposure
Assume: ISO200 requires 125 @ f8
Then: ISO400 requires 250 @ f8