As made evident by the notations on the lecture typescripts, filed as "Writings" in the previous series, Marceau and Rosen illustrated their talks on technical research and conservation with lantern slides. As the slides in this subseries make evident, they often borrowed directly from their published articles for their lectures. Many slides represent the same figures illustrations that accompanied several of Marceau's and Rosen's articles. The slides, however, are renumbered, no doubt to reflect a lecture sequence. For most of the lantern slides, however, no corresponding lecture typescript exists in these records.
Many of the slides consist of multiple images to allow for comparative analysis. These comparisons include an examination of the same detail of a work of art under different photographic techniques; different works by the same artist; a work of art before and after restoration; and occasionally a comparison of a confirmed attribution versus a questionable one. Many of the slides pertain to the paintings of Daumier and Corot. Several depict a conservation laboratory and equipment. While some of the slides filed as "Technical Study" duplicate images in the "Prints" subseries, there are additional study images, including what appears to be a specimen of varnish. Rosen probably took most, if not all, of these slides since many of the images correspond with his set of negatives described in the following subseries.