On the other hand, a theoretical mass difference of n × 1.0033 Da (i.e., CAMERA) has been used. Here n equals the depth of the isotopopologue mass. For example, an isotopologue mass depth of four corresponds to the mass range of the monoisotopic peak plus three isotopologues. This approach, even though elegant given that it does not require information on the molecular formula, does require an arbitrary mass tolerance as input.