An often better general approach may be to use the strip test to diagnose either the pure camber subcase or the more general (and common) case of bagginess. With camber, we would lay the web along a straight path (one side would thus be puckered), mark our two VERY carefully constructed perpendiculars, cut out strips from both edges and compare the lengths of the two edges. For very narrow webs we could merely cut the web down the middle. Another difference between the pure camber subcase and general bagginess is the troubles that are manifest. In the general case of bagginess, the concerns are most often wrinkling in a web line and lack of final product flatness. In the camber subcase, the concern would also include path control or registration in addition to wrinkling. One final note is that when you slit a wide web into narrower lanes, you inevitably get camber for strips cut near tight and baggy lanes.
I have given an hour-long keynote address on measuring and troubleshooting bagginess and also introduce a bit of it in my Web101 class taught in the public (AIMCAL’s Converting School), as video-on-demand and in-plant. A dozen case histories are also vlogged on my AllWebHandling channel on YouTube on clips Web201.45a-p. These free clips may be helpful for those poor souls struggling with either bagginess or camber. Of course, you could always just call me in to help speed up the process of diagnosing and treating these always chronic and often debilitating diseases.