I've been out of touch for more decades than I care to admit. At some
future point I must be able to project digital images onto a screen,
but it seems the days of the 35mm slide projector are over.
What is now the best way to project digital images onto a screen? The

I have here on my disk:
  * a TIFFEN 801 RETAINER RING MADE IN U.S.A.
  * a ring with just the tiniest bit larger outside diameter,
    *apparently* the same threads -- either one can screw into the other --