Do different microscopes and attached cameras differ in crop factor between each other?
Thus the conversion will make the results just more difficult to interpret.


I'm not personally familiar with this specific measurement, but in general, unless there is a specific convention in how to report a measurement, an absolute measurement should make the results easier to interpret, not more difficult (vs. % of image area). From a quick search, it seems like absolute measures of area, volume, and density are typically used when reporting chorionic villi measurements, so there isn't a convention to do it another way.