There is a trick I often use for animated sequences and the like to get the same exposure for all images using the “phisto” script. The idea is to generate a collective histogram of all the images and pass that to pcond like so:
phisto *.hdr > combined.hist
pcond -I < combined.hist img1.hdr > tm1.hdr
pcond -I < combined.hist img2.hdr > tm2.hdr
…
You can add whatever other options you like to each other pcond, just keep them consistent. This should result in the same tone-mapping operation each time.