Transparent layer constancy under changes in illumination color: Does task matter?

•We investigate transparent layer constancy across illumination changes.•We compare constancy in filter matching and filter identification.•Matching equates filter appearance and leads to incomplete constancy.•In identification same appearance not same transmittance is used as criterion.•The degree of constancy was larger with color scission than without.

If the perceived transmittances of transparent objects are matched across illuminants, only incomplete constancy is found. This implies that physically identical objects may appear different. Nevertheless, it was reported in the literature that subjects could almost perfectly identify such objects across illuminants, even if a transparency impression was suppressed by violating geometric transparency conditions. A potential interpretation of these findings is that (a) identification and matching rely on different criteria and processes and that (b) identification is solely based on low-level color information. We here present evidence against these hypotheses. Our results show that the best match, that is, the transparent object under the test illuminant that appears most similar to the standard, is also the preferred object in the identification task. Furthermore, we found that the degree of constancy increases in both tasks, if figural cues support a transparency impression and the accompanying color scission. We discuss the relation between matching and identification suggested by these findings.