Distance between x-ray source and film cassette should be:
3 distances
x ray source – midsaggital  : 5 Feet : 60” : 152.4 cm
mid saggital – film cassettes  : 15 cm Acc to Jacobson
                                                          18 cm = 7” = Gurkeerat sing
x – ray source – film casetes : 176 ~ 170 cm
                around 66”
60 inches
50 inches
65 Inches
55 inches