When opening .tiff/.psd files (3D renderings), Camera RAW opens automatically and displays a smaller preview with the filename urn-c2pa-…_thumb.png.src

We’re using the latest release of Photoshop on Windows. Since around late August 2026, opening certain .psd files has triggered one Adobe Camera Raw dialog for each affected layer. Each dialog shows a smaller, unedited version of the source image, including areas we cropped out before delivery. Our clients see this too when they open the delivered PSD, even though they never receive the original TIFFs.

We suspect a change in how Photoshop handles embedded previews when opening a PSD. In a test document with two affected layers, opening the PSD triggered two Camera Raw dialogs. After we deleted one of those layers and saved a copy, reopening it triggered just one dialog, showing the source image for the remaining layer.

We inspected that test PSD and found a TIFF preview stored in each affected layer’s Content Credentials (C2PA) metadata, labelled c2pa.thumbnail.ingredient. The previews matched the images and pixel dimensions displayed in Camera Raw. The dialog title follows the pattern urn-c2pa-…_thumb.png.src - TIFF. In the sample provided with this post, the preview measures 1024 × 576 pixels.

The source images come from V-Ray 7.40 for Cinema 4D 2026. Both the V-Ray Frame Buffer and the Cinema 4D Render Queue produce TIFFs that trigger the issue. Opening an affected TIFF directly also launches Camera Raw, even with TIFF support disabled in Camera Raw preferences. We reproduced this on two Windows PCs. Choosing Open As → TIFF and turning off automatic Content Credentials in Photoshop did not resolve it.