I saw an ep of Bonanza on TV Land a couple of weeks ago. The ep guest starred Jack Albertson. It concerned a man who killed someone and then used trick photography to falsely prove he was innocent. When the Cartwrights hear in this ep of photography they all act like its the first they ever heard of it. In another ep we see Hoss has a PHOTOGRAPH of his late mother in his room. If we apply reallife logic to this make believe the Cartwrights should already know what photography is in the trick photography ep!

Episodes of television shows aren't always aired in the same order that they
are filmed. The person in charge of continuity is supposed to spot these kinds
of bloopers, but sometimes one slips through the cracks. And add to that the
fact that shows later syndicated or shown on cable aren't necessarily aired in
the original network broadcast order, either.

Episodes of television shows aren't always aired in the same order that they
are filmed. The person in charge of continuity is supposed to spot these kinds
of bloopers, but sometimes one slips through the cracks. And add to that the
fact that shows later syndicated or shown on cable aren't necessarily aired in
the original network broadcast order, either.

Right, Collector. The blooper was either the result of overworked behind-the-scenes crewmember who didn't have time to check all the previous scripts or a crewmember who did look over the previous scripts but didn't catch the inconsistency (the bit about the photo of Hoss's mom was only briefly in the other ep and not that central to the plot).

PS the ep briefly about the mommy photo was the one where Hoss gets amnesia and a childless couple almost adopts him!

Well, if they acted like they never heard of it that was stupid. Photography was in the east since at least the 1840s and the west since at least the 1850s.