Appendix 4—table 1. Light flash peak wavelengths and intensities delivered by each of the 25 light-points in the stimulus array.

The given light intensities were measured at the light source by Hamamatsu Mini C10082CAH spectrometer, before 100-fold neutral density filtering. Thus, these values are estimated to be 10^2-3-times higher than the corresponding effective photon rates at the level of R1-R6 sampling (see Appendix 2—figure 3). Accordingly at the optical axis, the center LED (No.13), with the neutral density filter on it, evoked subsaturating (~20–35 mV) responses from Drosophila R1-R6 photoreceptors (Appendix 4—figure 4).

Light- Point	Peak1 wavelength (nm)	Peak1 intensity (106 photons/s)	Peak2 wavelength (nm)	Peak2 intensity (106 photons/s)
No.1	448	2.720	571	2.805
No.2	452	1.790	570	2.818
No.3	448	2.618	565	2.900
No.4	451	1.840	576	3.020
No.5	451	2.570	575	3.710
No.6	451	2.214	572	3.640
No.7	452	1.430	575	2.020
No.8	446	2.203	570	2.990
No.9	453	1.465	571	2.350
No.10	451	3.300	578	5.100
No.11	453	1.877	575	3.080
No.12	455	1.763	575	3.020
No.13	451	2.334	575	3.440
No.14	451	2.009	576	2.634
No.15	454	2.400	568	4.480
No.16	452	2.390	572	4.165
No.17	455	3.190	566	3.010
No.18	452	1.990	578	3.320
No.19	455	1.958	578	3.336
No.20	454	1.745	569	2.670
No.21	450	2.642	573	2.314
No.22	452	9.520	572	13.300
No.23	452	2.420	575	3.380
No.24	452	2.658	573	3.284
No.25	452	1.670	570	2.750