His work is defined by a formal and structured approach to composition. Baldus was frequently commissioned by the French government to document historic monuments and new engineering projects like the Chemin de fer du Nord. He preferred the calotype process, which utilised paper negatives to produce soft, tonal prints. His photographs of the cathedral in Bordeaux and medieval tomb sculptures possess a stillness that emphasises the permanence of stone. He avoided the clutter of daily life, presenting buildings as isolated, monumental objects.

Modern collectors value the architectural precision and muted colour palette of these early prints. The salted paper and albumen processes produce earthy tones that range from warm sepia to cool grey. These prints offer historical weight without the visual noise of contemporary photography. Because they focus on form and geometry, they suit minimalist interior design. His photographs of the Louvre or the Pont du Gard provide a quiet, scholarly atmosphere for a study or gallery wall.