**Research team (alphabetical order):** Geoffrey K. Aguirre, David H. Brainard, Joris Vincent The broad purpose of this project is to study the interactions between signals originating with stimulation of melanopsin and signals originating with stimulation of the cones. The specific experiment preregistered here asks whether a melanopsin-directed pedestal affects thresholds for detecting light flicker seen principally by the cones, where the cone-directed light flicker is admixed optically. This is a conceptual replication of a previously conducted and pre-registered experiment ([doi:10.17605/OSF.IO/58GCF][1]). In that experiment, the cone-directed light flicker was presented by the same device as the melanopsin pedestal. Radiometric measurements revealed that device imprecision created a stimulus artefact in one condition but not the other, which confounded explanation of the observed results. The current experiment presents the two stimuli optically admixed, which should reduce the likelihood of confounding stimulus artefacts. A change from the prior studies in this line of work is that the primary values of a three-primary projector are modulated equally to produce flicker that does not attempt to selectively target a luminance mechanism. The design of this experiment incorporates knowledge gained from a pilot version of the experiment run on author JV. [1]: http://