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Control [EEC] in the lens mount will correct for this because it "sees"
through the filter in place.
3. The chart below is a convenient guide to resetting the ASA Index on your
camera to compensate for the filter in use. Guide numbers that are shown
on the film package are now generally displayed as ISO numbers. These
are identical to the earlier ASA rating Index.
Convert ASA / ISO Index to FILTER FACTOR
Colour or Neutral Density Filter Factor
ASA
1.5 2 2.5 3 4 5 8 12 16 32
1000 650 500 400 320 250 200 125 80 64 40
800 500 400 320 250 200 160 100 64 50 32
650 400 320 250 200 160 125 80 50 40 25
500 320 250 200 160 125 100 64 40 32 20
400 250 200 160 125 100 80 50 32 25 16
320 200 160 125 100 80 64 40 24 20 12
250 160 125 100 80 64 50 32 20 16 10
200 125 100 80 64 50 40 25 16 12 8
160 100 80 64 50 40 32 20 12 10 6
125 80 64 50 40 32 25 16 10 8 5
100 64 50 40 32 25 20 12 8 6 4
80 50 40 32 25 20 16 10 6 5 3
64 40 32 24 20 16 12 8 5 4 2.5
50 32 25 20 16 12 10 6 4 3 2
40 25 20 16 12 10 8 5 3 2.5 1.6
Yashica Guy has rounded off results to the nearest ASA setting
