En la review que enlacé viene el dato del input lag:

If the LTDN50K321UWT looks like it would make a great big-screen gaming monitor, then you're right. With the TV set to its Game preset, and as much video processing as possible turned off, I measured its input lag at just 38ms. This is a highly respectable result for a 4K UHD TV, and shouldn’t have a negative impact on your gaming performance