Sorry, that's clearly incorrect for circumstances where the wider lens is even slightly near (or beyond) hyperfocal. Try it on dofmaster...at f22, 30mm @ 4ft. gives you 36.7 ft. of DoF vs. 300mm @ 40 ft. gives you 7.23 ft. of DoF. But at f2.8 it's only .91 ft. vs .89 ft.
Originally Posted by Q.G.
Again, it is just f-stop and magnification, but it's magnification at the point whose focus is being considered, NOT magnification at the plane of best focus. Since you can't keep all of the magnifications the same for different FsoV you get different DoF results.