Borbin the 🐱

While at Kualoa Ranch taking a 360x180° panorama, I also made a 1x2 panorama at a picturesque point. But both pictures were taken with different exposures using the auto setting. The left side picture is 1/500s f/8 and the right side picture is 1/400s f/7.1

1/500s f/8 to 1/400s f/7.1 is 2/3 of a stop ( ln( (7.1/8)^2 * (400/500) ) / ln(2) ), resulting in uneven exposures. See this excellent exposure calculator.
See also Uneven Exposures and correction.

The exposure alignment of the panorama stitching might not always be successful and can result in an exposure seam as in this example:

To avoid this, the pictures need to have matching exposures. In this case, the left side picture is made 2/3 stops brighter than the right side:

The 1x2 panorama with no exposure seam, only the reflection of the mountains: