Yes, as Brian said there are are around 28 episodes that only exist in kinescope form. For these, the original 2-inch video tapes are lost, and kinescope transfers to video are used for the TV, VHS and DVD releases. This is why a b & w episode will appear in the middle of a batch of color episodes.- kinescopes were only made on b & w film, and the color videotape is lost. Therefore the only extant copy of that particular episode is a b & w kinescope.
There is only 1 episode that does not exist in film or videotape- that's episode 1219.
All the pre-Barnabas episodes are complete on the collector's series videotapes.
For more info check out pgs 112-115 in the DARK SHADOWS ALMANAC: MILLENNIUM EDITION. Some nice article in that one ;-)