Question
ARW file is corrupted with purple line glitches
All of a sudden, a photo got “glitchy”purple lines in Lightroom CC. I had just opened it after editing a previous photo in an album.
The lines seem to be baked in the original ARW file:
- They are present on exported JPGs
- They are also there on the exported “original” file.
Thinking the file had somehow gotten corrupted in Lightroom (or in the Cloud), I deleted it from the Lightroom catalog and re-imported the clean file straight from a local backup. The glitch came back immediately — and so did all my previous develop edits.
This tells me two things: Lightroom is re-linking re-imported files to their catalog entry by filename, and — more worryingly — whatever operation originally caused the corruption is being applied again automatically on re-import. The backup file card is perfectly clean; the damage is being introduced by Lightroom itself.
Demo
Left: original .ARW file.
Right: corrupted .ARW file.
Although rare, it is not the first time this happens to me, I have other files to show if needed.
I asked Claude Code to compare the two RAW files (original + “original” reexported from Lr CC).
Here are its findings:
**File info:**
- Camera: Sony ILCE-7M3
- Compression: Sony Lossless (TIFF type 32767), 14-bit, 6048×4024
- File size: identical on both files (24,943,360 bytes)
- StripOffsets: identical (606,208) — the TIFF structure is intact
**Findings from binary diff (`cmp -l`):**
The SD card original and the Lightroom-exported file are byte-for-byte identical except for exactly **4 blocks of exactly 256 KB (262,144 bytes each)** located entirely within the compressed raw image data (StripData):
| Block | Absolute byte range |
|-------|-------------------|
| 1 | 13,893,633 – 14,155,776 |
| 2 | 15,990,785 – 16,252,928 |
| 3 | 22,282,241 – 22,544,384 |
| 4 | 24,379,393 – 24,641,536 |
Spacing: blocks 1–2 are exactly 2 MB apart, blocks 3–4 are exactly 2 MB apart, and the two pairs are exactly 8 MB apart. This is clearly deterministic, not I/O corruption.
**Conclusion:**
Lightroom's Export Original routine is overwriting 4 specific 256 KB regions of the losslessly-compressed raw pixel data. My hypothesis is that when Lightroom writes back internal metadata (MakerNote, private IFD, or preview), it miscalculates an offset inside the ARW TIFF structure and clobbers those 4 blocks. When the corrupted bitstream is decoded, the lossless decompressor produces garbage pixel values that demosaic as purple/magenta vertical bands.
The original file from the SD card opens and renders perfectly in every application. The damage is introduced exclusively by Lightroom.
The re-import behavior makes this worse: deleting and re-importing the clean file re-links it to the existing catalog entry, which re-triggers the corruption. There is currently no way to recover from this within Lightroom without keeping the SD card copy safe separately.
**Steps to reproduce:**
1. Import a Sony A7 III ARW shot in Lossless Compressed format
2. Apply any develop edits
3. File → Export → Export Original
4. Delete the file from the catalog, re-import the same clean file
5. Binary-compare any version to the SD card original
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