Working with the Filters
Let's assume that you have an NTSC LFF fielded media clip imported into FCP.
The first part of the process starts with FCP itself. By default, an NTSC FCP project will expect fielded media, with the default field order being lower field first. This is true for imported clips and generated sequences. Because this default setting will feed both fields as a frame into the viewer, and therefore the filter, this prevents the BCC Deinterlace filter from being able to see both fields, as the filter's algorithms expect to be handed separate video fields and not composite frames.
To set the sequence and media correctly for this project, we need to set the field interpretation to none in FCP for both the sequence and the media to be treated. This can be handled in the FCP Project Bin ... simply select the item that you wish to change, then scroll across to the Field Dominance column and Control + Click where it displays "Lower (Even)" and select None from the pop-up option window.
As you drag through the timeline you should be able to see only the separated fields in the clip composited together. Where there is enough movement in the clip, you will see the obvious field separation.
Now that the clip is able to feed both frames to the filter we are ready to start the film look process. Edit a portion of the clip that we are going to work with into the FCP sequence. If the clip is set as described above it should look like this:
The filters should be applied in the order as listed above for best results so let's add the first filter, BCC Deinterlace, from the list.