Think about it: two people are researching their family lines, one light skinned, the other dark skinned. When looking at family color photos taken before 1970, the two will see different things.
If they are color (Ektachrome images – everything turns pink with age – excepted) the white researcher’s people in the pictures will look defined.
But family members of the dark skinned people will be less defined.
It not just a matter of lighting. And it didn’t get fixed because dark skinned people mattered.