What makes the information contained in the artwork of Italian and Northern Renaissance reliable and/or not reliable?
Three significant elements in both Northern and Italian Renaissance artwork that make them reliable are perspective and surface detail and anatomical detail.
Perspective renders space and locale depiction reliable as one can asertain how shapes fit together in a three dimensional space.
Surface detail, as to a lady's lace or the play of light and shadow, render materials and objects reliable as one can determine that quality of craftsmanship and workmanship in productions of the time.
Anatomical detail renders physical proportions and development reliable as one can see the accurate representation of the human form and of the forms of other species.