Assertion: focal ratio's difference | /r/AtLocation | the order of millimeters
Facets:
Source sentences:
text: The curves are shown to match the relative difference between the curves of the fields, but the green lines are showing a 2" field of view so you can see that even by the edge of a 2" field, the blue line is standing quite proud of the black line, but remember, these are drawn to scale, so the tiny difference in the picture is on the order of millimeters, but that is all it takes to have severe field curvature.