Slowly transition from pitch black to normal light

Hello everyone,
Does anyone here know how to make the eye adaptation transition from pitch black to light slowly, instead of fast ? I know how to do it the opposite, and my current “setup” is this:

1 unbound post process volume with low priority, and 1 specific post process volume that has exposure to -6 and speed up to a value of 1 or .5 - so when I enter it, the camera slowly goes from normal light to pitch black.

But how do i do the opposite ?

One more thing - using the Blend Radius in the PP volume is not what I want, because the player char doesnt really exit that cave/PP volume. the player character enters a cave, as it moves forward it gets darker and darker and then it gets teleported to a random cave in the map (there are multiple caves) and as he moves out of the new cave, the exposure should increase. reason for doing this with pitch black caves is because i want the transition to be seamless