Aperture / shutter speed pairs that create the same exposure are theoretically equivalent because the same amount of light reaches the film/sensor. If you stop down the aperture while lengthening the time of exposure by one stop, then the total amount of light is the same in both cases. But will the two exposures really be the same?
I know in the old days photographers would often use dark rooms and small apertures and then just trickle in the light for a long exposure, and this would supposedly improve the tonality of the image.
Even though the amount of light is the same, there would seem to be a difference between a short blast of light versus a long trickle of light. For example, effects like bloom might be mitigated by a longer exposure.
So, is there a difference, or is an exposure just an exposure and that is all there is to it, no voodoo involved?