Cropping Source without loss of resolution

I’m trying to crop a 1280x720 video that contains a portrait view of paper that is 8.5x11 inches, or something similar. I want to make the paper fit the video dimensions with minimal black borders. The forums recommend the “Crop: Source” filter, but it’s not clear what the final size of the video will be from the filter parameters, which is causing extreme loss of detail. The parameters I’m using are: center unchecked, center bias 0, top 0, bottom 0, left 364, right 364.
Does that mean the final horizontal resolution is 1280 - 2*364 = 552? I set export resolution to 552x720 and the same for aspect ratio, but if I extract an image of the video using ffmpeg, the paper is scaled about 1/2; a tiny view surrounded by huge black borders (see attached image).

You need to apply the (zoom) or position, rotate and scale filter inside Shotcut.

How? When I apply the zoom filter, it cuts off the top in the preview, which only has no black borders on the top. Also, won’t that upscale a low resolution image into a uselessly blurry mess? And why is it being downscaled when I export, when the there are no black borders in the preview window?

Problem solved with:

ffmpeg -i tmp.mp4 -vf “crop=560:720:360:0” out.mp4

I would still like to know how to do this in shotcut, because the preview window is inconsistent with the exported video, which is scaled down by half with huge black borders all around. The preview in shotcut has no black border on the top and bottom.

Set the zoom value manually, do not use fit to screen!
The zoom in your case should be around 200%.

That cuts off the top and bottom.

This is probably the issue. The proper way is to create a custom Video Mode, which sets the resolution of the timeline. It sounds like you did Export > Advanced > override resolution. That override does not crop. It scales.

You are using the correct filter by using Crop: Source. You do not need any zoom filters.

Question: Do you have preview scaling turned on?

See Apply to Source in