The number of bits of numeric precision available for each feature channel.
Mac Catalyst 13.0+
Metal Performance Shaders
This is precision, not size (float is 24 bits, not 32; half-precision floating-point is 11 bits, not 16; Snorm pixel formats have one less bit of precision for the sign bit, etc.). For formats like MTLPixelFormatB5G6R5Unorm, this value is the precision of the most precise channel (which is 6 in this case). When this information is unavailable, typically for compressed formats, this value is 0.