Thanks, TinMan, that was exactly what I was looking for

Here it is: . You're right about the elevation changes. That happens when
the light intensity goes from low to high and the shooter's eye iris
gets smaller. When that happens, the aiming bull appears larger and
the front sight post will still appear the same size, but when touching
the bottom of the apparently larger bullseye, the shots will go low.
In darker (dimmer?) light, the eye's iris gets larger and the bullseye
appears smaller causing the front sight post to be closer to the center
of the bullseye; the shots go higher. The `light's up; sight's up'
rule of thumb is very correct for post front sights whether they are
hooded or not. Typical correction varies from a quarter to almost a
full minute elevation change depending on the person's eyes and light
condition changes as well as atmospheric conditions. When aperture
front sights are used, this doesn't apply; the bullseye centers in the
round aperture regardless of how big it appears, but the aperture size
might need to be changed to allow a better sight picture.