Lightroom Classic Bug Report

Title

Lightroom Classic reports "The file appears to be unsupported or damaged" for valid Lightroom-generated HDR DNG files. 

Product

• Adobe Lightroom Classic 15.4.1

• macOS 15.7.x (Apple Silicon)

Summary

Lightroom Classic reports that certain HDR DNG files are unsupported or damaged.

However:

• Adobe Camera Raw opens and edits the files without any problems.

• Adobe Photoshop opens the files without any problems.

• Adobe DNG SDK Validator validates the files successfully.

• Lightroom Classic itself reports the files as invalid ("Validate DNG").

The same behaviour occurs in a brand-new Lightroom catalog and also with backup copies of the same files.

Steps to Reproduce

1. Open Lightroom Classic 15.4.1.

2. Import or open the affected HDR DNG.

3. Lightroom reports:

The file appears to be unsupported or damaged.

The file also cannot be imported into a brand-new catalog.

Expected Result

The HDR DNG should open normally, since:

• it is a Lightroom-generated HDR DNG,

• it validates successfully with the official Adobe DNG Validator,

• it opens correctly in Camera Raw,

• it opens correctly in Photoshop.

Actual Result

Lightroom Classic refuses to read the file and reports it as unsupported or damaged.

Additional Information

The affected files were created using:

Photo Merge → HDR

inside Lightroom Classic.

They are not camera-generated DNG files.

Validation Results

Adobe DNG Validator

Validating "..._Q8F1189-HDR.dng"...Raw image read time: ...Transparency mask read time: ...Linearization time: ...Interpolate time: ...Validation complete

No validation errors are reported.

Adobe Camera Raw

• Opens successfully

• Image is fully editable

• Local adjustments work

• Zoom works correctly

Adobe Photoshop

• Opens successfully

• Image data is intact

• File can be edited normally

Lightroom Classic

• Import fails

• Library cannot read the file

• Develop cannot open the file

• "Validate DNG" reports the file as invalid

DNG Metadata

DNG Version:            1.7.0.0Backward Version:       1.7.0.0Process Version:        15.4Preview Application:    14.4

Additional Notes

The same behaviour occurs with:

• backup copies of the affected files

• a completely new Lightroom catalog

This suggests the issue is independent of the Lightroom catalog itself.

Several HDR DNG files created in different years (2017–2024) appear to be affected.

The files are valid according to the Adobe DNG SDK Validator and remain fully readable in Camera Raw and Photoshop.

Regression

The same HDR DNG files open correctly in Lightroom Classic 15.3.
The issue appears only after updating to Lightroom Classic 15.4.x.

Feel free to contact me directly if any more infomation is needed.