Ferroelectric domain wall conductivity (DWC) is an intriguing and promising functional property that can be elegantly controlled and steered through a variety of external stimuli such as electric and mechanical fields. Optical-field control, as a noninvasive and flexible tool, has rarely been applied so far, but it significantly expands the possibility for both tuning and probing DWC. On the one hand, as known from second-harmonic or Raman micro-spectroscopy, the optical approach provides information on DW distribution and inclination, while simultaneously probing the DW vibrational modes; on the other hand, photons might be applied to directly generate charge carriers, thereby acting as a functional and spectrally tunable probe to deduce the local absorption properties and bandgaps of conductive DWs. Here, we report on investigating the photo-induced DWC (PI-DWC) of three lithium niobate crystals, containing a very different number of DWs, namely: (A) none, (B) one, and (C) many conductive DWs. All three samples are inspected for their current-voltage behavior in darkness and for different illumination wavelengths swept from 500 nm down to 310 nm. All samples show their maximum PI-DWC at 310 nm; moreover, sample (C) reaches PI-DWCs of several microampere. Interestingly, a noticeable PI-DWC is also observed for sub-bandgap illumination, hinting toward the existence and decisive role of electronic in-gap states that contribute to the electronic charge transport along DWs. Finally, complementary conductive atomic force microscopy investigations under illumination proved that the PI-DWC indeed is confined to the DW area and does not originate from photo-induced bulk conductivity.