If your panorama shows abrupt changes in brightness, first be sure you have selected Abilita corrispondenza esposizione / Enable exposure matching.  If you did not enable it when you used the New Project Wizard, you can enable it now by running the Proprietà fusione / Blending properties dialog box (Strumenti / Tools menu).

If this does not correct the exposure matching from one image to the next, please read “Adjusting exposure matching and brightness falloff” in this chapter for instructions about correcting the exposure manually: