JPEG XL Lossy export outputs 8-bit despite 16-bit being selected

On my main PC, I noticed that the JPEG XL lossy compression color space AdobeRGB appeared off, and when I checked the file details I realized it had become 8-bit.

All JPEG XL lossy compressions I have created so far were created in 8-bit.

When exporting on the secondary laptop I use, I was able to create a normal JPEG XL lossy compression color space AdobeRGB 16-bit.

I will reinstall and check again.

Please explain what you mean by “color space Adobe RGB appeared off”.
Where did you see that the image was 8-bit? In Photoshop?
Would you mind sharing an image here?

メインPCで作成していた、JPEG XL　非可逆圧縮　色空間 AdobeRGB　の発色が狂っていたのでファイルの詳細を見ると８ビット　になっていたのが気づきました。

今まで作成した JPEG XL　非可逆圧縮は8ビットで作成されていました。

サブで使用しているノートパソコンでエクスポートすると　色合いは正常なJPEG XL　非可逆圧縮　色空間 AdobeRGB　16ビットが作成できました。

再インストールしてチェックしてみます。

I tested this on both my Win11 machine and MacBook Pro M1 Max. LrC V 15.5.1 and PS V 27.10.0 on both. 

A jpg XL exported to 16 bits just fine on both machines as reported in PS Image Mode.

I can’ reproduce this on LR 15.5.1 / Mac OS 26.6.2. When I exported a raw with these settings:

The exported file is 16-bit, according to the “jxlinfo” utility:

$ jxlinfo -v D300hSLI0100.jxl 
Box:
  type: "JXL "
  size: 12
  contents size: 4
JPEG XL file format container (ISO/IEC 18181-2)
Box:
  type: "ftyp"
  size: 20
  contents size: 12
Box:
  type: "jxlp"
  size: 23
  contents size: 15
JPEG XL image, 4288x2848, lossy, 16-bit RGB
Number of color channels: 3
Number of extra channels: 0
Have preview: 0
Have animation: 0
Intrinsic dimensions: 4288x2848
Orientation: 1 (Normal)
Color space: RGB
White point: D65
Primaries: sRGB
Transfer function: sRGB
Rendering intent: Perceptual
Box:
  type: "Exif"
  size: 828
  contents size: 820
Uncompressed Exif metadata: 828 bytes
Box:
  type: "xml "
  size: 13082
  contents size: 13074
Uncompressed xml  metadata: 13082 bytes
Box:
  type: "jxlp"
  size: 1479167
  contents size: 1479159

Hi, ​@康樹310155101or5, admittedly, I didn’t know much JPEG XL, or whether it can support 16-bit and I did find one reference for that. But, traditionally jpg/jpeg images are 8-bit images. Nonetheless, when I tried to save a TIF-16 bit into a JPEG XL, they all came out as 8-bit. So, I suspect my original thought was correct, and they cannot. In fact, I found that Chrome stopped supporting JPEG XL in 2022 for lack of reason to support it.

I suspect, from what research I did, that it can only support 8-bit. If you want 16-bit, you’ll have to stick with PSD and TIF documents. I also suspect that this, like JPG 2000 will cease to be important at all in the future. But, that is speculation, I do not know for sure.

I cannot reproduce this with LrC 15.5.1 on Windows.
When I open the exported Jpeg XL lossy file in Photoshop, it’s 16-bit.
How did you come to the conclusion that the file is 8-bit?