Peter

There are so many versions of compressed Tiffs that it's a minefield, they should be avoided unless you are sure you are using a version which you know is compatible. Even then, there are few reasons to use them as large files are not the problem they used to be. This is not a new problem, I used to run into it 10 years ago when I was still working - there has never been a real standard.

Brian

I agree with the minefield statement.  TIFF file reading, especially 16 bits, is what it is.  I will not be changing anything WRT TIFF reading.  When I save a 16 bit TIFF compressed with LZW in PhotoShop or LR, it reads fine in QU so I suspect GIMP is using some non-standard format such as "per channel" pixel order or ZIP compression.  The current TIFF support in QU supports the greatest number of common formats.  If I change it so that it's happy with GIMP, then it'll be incompatible with Lightroom or PS.  If I change it so that it's compatible with 16 bit Lab color, then it won't read 16 bit grayscale TIFF's, and so on.  So it's always a compromise.  The TIFF reader that I use now is the one that is compatible with the most permutations that we see.  Needless to say, I'd rather it be compatible with PS and LR than GIMP.  So if you are using GIMP and GIMP doesn't have a way to turn off whatever non-standard file saving option is causing the problem, you're stuck with uncompressed.

Also, keep in mind that to be reading/saving 16 bit/channel TIFF's, you have to be using one of the "unstable" builds as the latest official release doesn't support 16 bit TIFF's.   So it's very possible that they have issues with 16 bit file saving in those pre-release builds.

Edit: After further investigation, if you click "Advanced" at the bottom of the TIFF export dialog (same dialog as the one where you select LZW compression) and you uncheck "Save thumbnail", QU can then read the saved TIFF.  They may have a bug in TIFF file saving in that unstable release.

Regards,
Mike