Hi, I'm Pete. Welcome to JustAnswer! I'm reviewing your question now, and will post back with your reply ASAP.
Gerry, you are correct - to attach a lens filter, you will need to use the FA-DC67A Filter Adapter.
You don't need another lens cap -a lens filter and lens cap cannot be attached to the camera at the same time.
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Hi, just checking in on your question, do you need any further assistance?