"veiling glare" is the term you are describing...
it forms as a strong haze over the image that washes it out and takes contrast away....like if you turn the brightness up all the way on a TV or computer monitor
most really good scopes prevent with this with good baffling and painting the edges of glass etc.... it happens in binoculars as well
even a zeiss conquest level scope should handle that pretty easily..
i dont see it in my swarovski but ill be honest i havent seen it from any scope in awhile, any scopes with 300-400 price tag and up at least
Im sure the new hi tech Leupold reticles made with "Electra-Form"tm Technology,
has taken care of the problem.........