Johnny Carson Sex Tape Will Go to Highest Bidder ... But There's a Catch

The person who has a copy of the Johnny Carson sex tape now wants to sell it ... but potential buyers have to blindly cough up a fortune just for the chance to see it.

The attorney repping the guy who has the tape tells TMZ ... his client will hold viewing parties for people interested in buying the 70's home video showing long-dong Carson banging one of his wives.

Now get this -- in order to even see the tape ... prospective buyers must make a blind bid. The seller is not setting a price. He'll just review what's on the table.

And it gets even crazier. To qualify to see the tape, prospective buyers must show they're serious by depositing their bids into an escrow account. And, like Carson's schlong, only huge offerings will make the cut.

After the screening, prospective buyers will be invited to up the ante.

And one more string attached. The winning bidder must sign a document saying it cannot be sold commercially -- it's solely for a private collection. And, if the buyer violates that ... he or she will get socked with a huge financial penalty.