It is disappointing to see the blinds in place on the skylights at the Whitechapel Gallery as my memory is always of the galleries filled with natural daylight. I was told that this was to protect some of the works from UV light. I do find it strange that the glazing does not have UV filtering but understand that any light level may be detrimental to some materials!
The Eva Hesse show May 4th - June 17th 1979 was not, as I recall, given special treatment but that is before the conservation orthodoxy became fully established, I guess!