Satin stitch vs tatami fill.

Satin lays long stitches side by side across a shape so the thread stays on the surface and catches light, which is why lettering, borders and small logo elements are satin. Tatami covers an area with short stitches in offset rows, flat and matte, and it holds its shape over sizes satin cannot. Width is the dividing line, because a satin stitch long enough to catch a zip or a fingernail will eventually be pulled out. Wilcom's answer is auto split, which breaks the long stitch while keeping the satin look, with 7.00 mm suggested as the length that preserves the effect (Wilcom EmbroideryStudio help). The density trap runs in both directions: tighten satin spacing everywhere to hide a thin sew-out and the penetrations perforate the fabric, the thread starts breaking, and a head that stops every few hundred stitches costs more than the job earns. Open a tatami fill up for speed and the travel runs and row patterning show through, worst on tight curves where the flat fill has to turn (tatami density).