I think that adjusting with ANTI-ALIAS / DEBLUR (cmd: preblur) will produce better results than adjusting the sharpening with SHARPEN (cmd: blur).
preblur
Adjusts both the antialiasing and deblurring strength relative to the amount of aliasing and blurring in the input video.
blur
Additional sharpening of the video. Use this if the input video looks too soft.
The value set should be relative to the amount of softness in the input video - if the input video is already sharp, higher values will introduce more artifacts.
For the ANTI-ALIAS / DEBLUR, a PLUS will set the value to DEBLUR and make the image sharper. Conversely, a MINUS will result in ANTI-ALIAS, making the image blurred.
