Unable to reopen a File created by TIFF export

[Mclimax]

Hello together

After doing a file stack of two panoramic pictures (one foreground / one background), both TIF, I made an Export to TIFF. After that I closed the programm and reopened it for all the following work.
I spend a lot of time on different layers and did also save the Layers in the TIFF-File. Then I closed the huge (2.5GB) File.

Now the File can be viewed in Lightroom, IrfanView, Windows Picture Viewer, ... All these are working. But Affinity Photo can't reopen the File.

Message
"Failed to open TIFF File
File type is not supportetd."

How can it be, the File was created with Affinity? Is there a File size limit? Any other ideas?

System:
Windows 10 Home 64bit
Affinity Photo Version 1.7.3.481

I need your help. It's ok to do this File again if necessary, but I don't want to spend again that much time with the same result.

Thx in advance
Manuel

[Michail]

12 hours ago, Mclimax said:

" ... All these are working. But Affinity Photo can't reopen the File."

Interpolate a copy of the source file down (Ctrl+Shift+I) Then export it to TIFF again. This way you can find out if the file size is the cause. If the problem persists, could you perhaps provide us with a heavily downscaled version (Color depth and number of pixels)? Then we can find out if this might only happen to you.

[Mclimax]

On 1/4/2020 at 2:21 PM, Michail said:

Interpolate a copy of the source file down (Ctrl+Shift+I) Then export it to TIFF again. This way you can find out if the file size is the cause. If the problem persists, could you perhaps provide us with a heavily downscaled version (Color depth and number of pixels)? Then we can find out if this might only happen to you.

Hello Michail,

Thank you for your Ideas. I did a few tests to verify if the filesize can be the cause or not.
It seems that really the filesize is the main cause of the problem. I've tested many times with the same results with the following procedure:

1. Create a File with several layers. Export to TIFF.
2. Close the temporary File, reopen the TIFF.
3.a) If TIFF-size is below 2 GB I can open it again and again. No problems --> Add one more layer.
b) If TIFF-size is above 2 GB I can't open it with Affinity, but with all other programs named in the thread-opening.

After research of the TIFF-specs I found this description on Wikipedia which indicates that issues with 2 GB TIFF Files are known:

Quote

BigTIFF

The TIFF file formats use 32-bit offsets, which limits file size to around 4 GiB. Some implementations even use a signed 32-bit offset, running into issues around 2 GiB already. BigTIFF is a TIFF variant file format which uses 64-bit offsets and supports much larger files.^[29] The BigTIFF file format specification was implemented in 2007 in development releases of LibTIFF version 4.0, which was finally released as stable in December 2011. Support for BigTIFF file formats by applications is limited.