Kappa - help with curvature analysis of poor contrast image

Hi Kappa users and developers,
I have used kappa previously and it worked really well to perform curvature analysis of beam.

However, for the present set of data, it becomes really hard to select the points on beam due to SEM image contrast. I tried playing/adjusting the contrast and brightness settings in imagej but of no use.

Any tips on how to properly select the points on beam for curvature analysis using kappa for the attached image. !

Anuj Bisht,AuPd_W2_step1_200C60min_04.tif (866.7 KB)