How to prevent this exposure/tonal shift when stitiching an HDR panorama in Photoshop?

Question

I'm trying to create an HDR panorama.

I have 8 photos with 3 exposures each (-1, 0, +1 EV). For each one, I used PS's merge to HDR functionality and chose 32 bit.

I have 8 files A, B, ...H.psd that I now want to merge to a panorama. The stitiching works great, but the last image in the panorama is a lot darker in the panorama than it is on its own.

On the left is the image on its own. On the right, you see the part of the panorama that's made up of the image. I added red outline around the contour of the mask for that image.

Why is the image so much darker in the panorama? How can I prevent this?

I noticed that a lot of tools don't work in 32bit mode. Is it recommended to stay in 32bit mdoe throughout the entire process? Or should I tonemap (or whatever it's called) each part of the panorama down to 8bit again and then stitch the panorama in 8 bit mode?

Wait, we always take a second set of images in case something goes wrong, right? Well, the second set of images produces even weirder results. I only took 7 images (A-G). Take a look at the screenshot from PS that illustrates the problem below.

The individual images on top have a similar look the exposure is the same. I arranged the windows in a way that the single images mimic their position in the panorama. The stitched panorama shows strange differences in exposure (?) throughout the panorama.

Wtf?

Answer 1

I don't have an explanation on why one image becomes darker when merged, but perhaps "reversing" the process might help, first creating three panorama images, one per exposure setting (-1, 0, +1 EV), then running the HDR processing one those three images?