Figure 2.

(a) Iris radiance measurements taken with a radiospectrometer aiming at a secured, slightly anesthetised fish at 20 m depth. (b) Substrate transect device with reflectance standards in the center (left to right): black standard, shaded diffuse white standard (PTFE) and exposed diffuse white standard (PTFE). The latter was used for the calculations presented here. Spectral measurements were taken approx. 1 cm above each of the 10 cable binder tips (yellow spot) while pointing horizontally at the substrate. The length of the central black carrier is 22.5 cm. (c) Substrate radiance measurements were taken at 5 and 20 m depth using a calibrated spectroradiometer in a custom‐made underwater housing (BS Kinetics)