sharpen filter preview not exact

[herr_k.]

sharpening a picture with "apply to image" on,
the "after" in the preview is different than the actual "applied" picture:



and i noticed also the "before" doesnt look like the original neither? meaning when you untick the "apply to picture" the "before" dowsnt look like the original...

[xnview]

and i noticed also the "before" doesnt look like the original neither? meaning when you untick the "apply to picture" the "before" dowsnt look like the original...

Right, the picture used is a thumbnail not the original