This, this, this. Something made of light or plasma or whatever shouldn't cast a shadow. The biggest offender in my book is in RotJ when Vader is walking up the Emperor's stairs towards Luke before he was unwise to lower his defences. Vader has the saber in front of him, then swings it out to the side, and it casts a stick shadow on the ground. Also when Vader and Luke are having their final swings towards The Pit its pretty bad. I don't recall any in ESB.

Ady, are you planning on eliminating lightsaber shadows when you can?

That shadow appears and to ROTS too,in the very first lightsaber battle with Dooku. When obi-kenobi get pushed by Dooku you can see the pod shadow.