It is the same scene, the same lightning, just different ISO settings and shutter speeds to keep the same EV. Brightness of all images should be the same, and it is with camera JPEGs, but not with RAFs developed in darktable.

With this feature request I am asking to respect this Fujifilm's tag and automatically apply EV correction depending on value in this tag, so that user is freed from doing that manually.

According to discussion on IRC, one possible way of implementing this: turning on exposure module by default for newly imported RAF images with this tag, and automatically entering EV correction depending on value in tag.

Personal opinion: if architecture of darktable allows it, maybe the code of exposure module can be reused and new module "Raw exposure correction" can be created. This module would be executed just before exposure module, would essentially do what exposure module does, but would lack any user's inputs (except ability to turn module on/ff). Exposure correction value would be internally taken depending on mentioned tag, and shown to the user in this module ("Exposure correction applied: X.XX EV"). I think it would be more clear to user in this way than preapplying correction to the slider in exposure module.

Examining this, I took a "test JPG" image for optical comparison. It appears the test JPG is the same as the view -0.7 image. As a result, the correct exposure to apply is not "+2.2" for ISO 6400, but actually +1.5 (2.2 - 0.7).

As a result, you only need 5 presets to exposure to correct this.

+0.1 at ISO 2500+0.5 at ISO 3200+0.8 at ISO 4000+1.1 at ISO 5000+1.5 at ISO 6400