Enhancement (in mag) of a purely stellar disk by nebular (line and continuum) emission vs. z. The case of a moderately evolved (0.6 Gyr), continuously growing disk with a rest-frame EW(Hα) ∼ 200 Å is shown in the upper panel, whereas a very young disk (16 Myr) with an EW(Hα) ∼ 10³ Å is shown in the lower panel. Vertical bars mark the age of Universe (in Gyr) at some z intervals where nebular lines enhance the surface brightness of the disk most. An insight from this figure is that NIR photometry is more affected by nebular emission than optical photometry for z > 0.6.