Bit depth of lossy DNGs?

[JacquesCornell]

How can I determine the bit depth of a lossy compressed DNG made with the JPEG XL engine? I convert an adjusted RAW to a lossless DNG, then use Lightroom Classic or DNG Converter to generate from that a lossy compressed DNG. That lossy compressed DNG seems to have the same dynamic range and tonal malleability (5 stops!) as the original RAW file, so I have to assume it's more than 8 bits, as I'd expect a similarly abused JPEG to fall apart.

[johnrellis]

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Raws converted to lossy DNGs by Library > Convert Photo To DNG have a nominal bit depth of 16 bits per channel (nominal, because the actual depth depends on the camera sensor which is typically less). You can see particulars about a DNG using the Metadata panel's DNG tagset: