Weston Master II Light Meter

Weston Film Speed Scale Vs ISO: (Please note differences in the lower film speeds are so similar, shooting on negative film without compensating will result in very useable photos). Another footnote, the US model was introduced sometime in 1945-1946, whilst the UK version slightly later in 1952. ISO - Weston 3 - 2.5 4 - 3 5 - 4 6 - 5 8 - 6 10 - 8 12 - 10 16 - 12 20 - 16 25 - 20 32 - 24 40 - 32 50 - 40 64 - 50 80 - 64 100 - 80 125 - 100 160 - 125 200 - 160 250 - 200 320 - 250 400 - 320 500 - 400 640 - 500 800 - 640 1000 - 800 1250 - 1000 1600 - 1250 2000 - 1600 2500 - 2000 3200 - 2500 Source: http://www.westonmeter.org.uk/speeds.htm