Abstract: A method of setting recorded data bit cell length on an APS film magnetic layer in a camera of the type having apparatus for normally setting bit cell length as a function of measured film transport velocity. The method comprises detecting the occurrence of an invalid film velocity measurement and substituting a default data recording frequency that results in a recorded bit cell length on the film which ensures that a maximum number of intended data bits are recorded in a given available length of data track which might otherwise not result if the invalid film velocity measurement were used to set the recorded bit cell length.