The National Hockey League adopted a new playoff format yesterday and the Capitals are jubilant. If they pick up where they left off, and all-their rivals stand still, as it were, Washington figures to have a beck of a better shot in 1977-78 than in 1976-77 to make the postseason lineup.

Previously, the top three clubs in each of the four divisions qualified. Now, by a 12.6 tally - Cap president Peter O'Malle casting the deciding vote at the league meeting in Toronto make it automatically, along with the four teams with the next most points in the standings, regardless of division or conference.

Last season, the Capitals were 19 points behind third-place Pittsburgh in their division and had no chance, in the late going of making the playoffs: fans got turned off. But the Caps' 62 points were just two - a win or two ties - shy of the 64 that put Minnesota in the chase for the Stanely Cup. And Chicago got in with 53 - while the New York - Pangers, with 72, didn't A change figures.

So there are your 12 playoff contenders - whoops, there are 12 of your 16 contenders for the venerable mug. The world Hockey Association teams (six, probably) to be taken in by NHL., if the merger developes as planned, will play in their division all year, all right, but will send their best into the playoffs against regular NHL, opposition from the first round on . . .