  We investigate the properties of the photon Bose-Einstein condensate in the
limit of small mode spacing. Alongside the well-known threshold of the phase
transition at large mode spacings, we find an emergence of a second threshold
for sufficiently small mode spacings, defining the crossover to a fully
condensed state. Furthermore, we present our findings for the mode occupations
in the precondensate or supercooling region towards the continuum limit.
