The full array local dimming of the 2018 Sony X900F is decent and better than most LED TVs. It's a small upgrade when compared to the 2017 X900E. The X900F performance is more similar to the 2017 Sony X930E when set side by side, although the X930E has slightly less abrupt transitions of the zones on movements.

Very similar performance to the Samsung Q8FN. The X900F has deeper black levels, but there is more visible blooming.

When set to 'High', the feature is very good at limiting blooming and keeping a good overall black level, but on some occasions, it may be a bit too aggressive as small highlights can get dimmed on fast movements. Therefore, if you notice this behavior, you can set it the 'Medium', and it should behave more conservatively.