InDesign doesn't export 16 bit grayscale or 48 bit color images
Tested on version: 20.2 x64
Dear Adobe Support Team,
When importing high bit-depth images—such as 16-bit grayscale or 48-bit/64-bit color (TIFF/PSD formats)—into Adobe InDesign, we’ve observed that even when disabling down-sampling and compression, the exported PDF converts these images to 8-bit grayscale or 8 bits per component for color (i.e., 24-bit RGB or 32-bit CMYK), rather than preserving the original bit depth.
While we understand that limitations may exist within the current Acrobat SDK, it is important to highlight that:
The Adobe PDF Library SDK (PDFL SDK) explicitly supports the creation and reading of 16-bit image objects in multiple color spaces. (https://opensource.adobe.com/dc-acrobat-sdk-docs/pdflsdk/apireference/index.html)
The Adobe PDF Print Engine (APPE) now offers native support for high-bit-depth (16 bpc) images.
Manual replacement of images inside a PDF with 16-bit versions still results in correctly preserved 16 bpc display, confirming that the PDF format itself is not a limitation.
Given these capabilities within Adobe’s own ecosystem, we kindly request that InDesign be updated to optionally preserve original image bit depth when exporting to PDF, particularly in professional print workflows where tonal fidelity and HDR imaging are critical.
Please refer to the attached image samples for confirmation and visual reference.
We appreciate your support and look forward to your guidance on whether this feature can be implemented or if a workaround exists via scripting or SDK.
Thanks.
Raphaël “bearofjupiter” BOULEUX
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Uncompressed exported PDF file from InDesign can be download here: https://www.dropbox.com/scl/fi/b70jbp4pi8f603s8xntvh/EXPORTED_FROM_ID_BOBST_GrayScale_TestForm_A3.pdf?rlkey=x2w56c5rgq10ksfehhffeiguc&st=eohojd45&dl=1