Venus' magnitude during inferior conjunction
I found references which indicate that Venus usually goes dark.  Check out the graphs in this paper for one example.  

The exceptions happen when Venus' orbit, which is slightly out of the ecliptic, brings it to inferior conjunction when projected onto our (Earth's) orbital plane, but Venus remains at a slight angle relative to our viewing lines.  

From UniverseToday,   


  Not all inferior conjunctions of Venus are created equal. The planet’s
  orbit is tilted 3 degrees with respect to our own and can thus pass a
  maximum of eight degrees north or south of the Sun. Venus last did
  this on inferior conjunction in 2009 and will once again pass a
  maximum distance north of the Sun in 2017. For the southern
  hemisphere, the red letter years are 2007, and next year in 2015.