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”