Sharpen function

[flier4]

I understand what the sharpen filter does. What I cannot find out is what does the size function do that is associated with the sharpen filter.

[sauron]

Sharpen Video Filter

[image] The frei0r plugin description says, “Unsharp masking (port from Mplayer).” The mplayer man page says it does gaussian blur or a sharpen using an unsharp mask routine. The underlying plugin code range is [-1.5, 3.5] where 0 is the switching point between blur and sharpen. Thus, 50% in Shotcut converts to 1.0 in the plugin code, and the switch point where there is no change is 30% in Shotcut. See also https://en.wikipedia.org/wiki/Unsharp_masking The Size parameter controls the amount…

[RilosVideos]

Size relates a bit to “radius” in the traditional Unsharp masking filter, know from Photoshop e.g. Important is to understand that the default values of 50%/50% already mean a tremendous amount of sharpening! In my opinion this is already too much in most cases! I normally set the values to 40…45% for both parameters. That is already enough in most cases. When you do too much, you will see sharpening artefacts like halos around objects and it doesn’t look naturally. If your images are quite blurry you may try higher values for size (and/or amount).

[flier4]

Thanks everyone, So I take it from these posts that the size will control the halo effect. The smaller the size (to a point) the less halo effect. So a setting such as 40/30 or 50/40 would be better than say 50/50 to reduce the halo. Correct?

[RilosVideos]

More or less. Both size and amount contribute to halo artefacts if the values are too high. If size is too high, the halo might get broader. If amount is too high and size small halos are smaller but more intense. You should avoid both! Normally settings between 40 and 50 for both values are fine. Just do a visual judgement