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@NotMyFault Thank you for your efforts! Indeed, it may just be a limitation of the PDF format itself. But, strangely, the images included in the PDF files exported from Affinity Designer are apparently formatted as 16 bit (although their internal data seem to be compressed to 8 bit). @Alex M I use Affinity Design to make scientific figures, so it would be nice to be able to make a PDF with 16 bit color depth so the quantitative data of the images remain uncompromised.

@NotMyFaultThank you for your suggestion! Attached please find the original 16-bit grayscale TIFF file, and three PDF files that were exported from Affinity Designer with three different document color modes. According to pdfimages, all the three PDF files contain 16 bit-formatted images. However, they seem to have only 8-bit tonal depth in practice, according to imagemagick. It might just be a limitation of the PDF format itself. Any ideas will be appreciated. Gray16.pdf original image.tif RGB16.pdf RGB32.pdf

When I exported PDF files that contain 16-bit grayscale images, I found that the actual data are somehow compressed to 8 bit and have lost their original tonal depths, even though their apparent formats are kept as 16 bit; after PDF export, the upper 8 bit and the lower 8 bit of the images become identical as follows. This was reproduced in both macOS and Windows versions of Affinity Designer 1.10.5. (771,771,771) #030303030303 grey1(1285,1285,1285) #050505050505 grey2(2056,2056,2056) #080808080808 grey3(2570,2570,2570) #0A0A0A0A0A0A grey4

Dear James, Thank you very much for the instruction and it worked beautifully! I think I can use the workaround for now. Hopefully the developers will implement it in the near future.

Dear James, Yes, I could verify that the TIFF file you attached (16bitGray copy.tif) can be correctly opened as 16-bit grayscale in both Affinity Photo and Affinity Designer. Detailed instructions will be truly appreciated.

Dear Walt and James, Thank you for the valuable information and inputs. I really wish there is a way to "tell" Affinity Photo that it is grayscale upon opening. I can manually change the color format after loading, but then the image has already lost the gray level resolution. Photoshop, Image J and GIMP etc. can somehow correctly recognize it as 16-bit grayscale.

Dear Gabe, Thank you, here is an example. 16bitGray.tif

When I tried to open 16-bit grayscale TIFF files in Affinity Photo (Mac), they are always opened as 8-bit RGB. Is there any way to force opening as 16-bit grayscale?