Thanks for your responses - & you're not nit-picking
This 'generic' chart is based upon manufacturer's printed materials, but does -of necessity- have some compromises ... which of the 4 "APS" sensor sizes do I go with? or do I compromise??
Equally -for example-, if I look at any of the Fuji or Panny range of superzooms, I read their "35mm equiv" lens ranges & their manuals describe angle of coverage for the zoom. Equating this 'compromise' with the 35mm table gives me certain results that do not always stack up ... thus another series of compromises
The chart is designed to give my students, often 'newbies' some visual grasp of the angles-of-view of lenses, and the differences between them
I will however go back to the source info & double check the 18 / 28 / 50 alignments - so if I have made an error, thanx for helping to make the chart even better
Otherwise - does it help you to work out lens focal length & angles of view??