Hi Brian!
I have opened your .cr2 file with the gimp in my appimage, did a basic processing in PhF, where I only changed the WB using “Spot” and clicking on some part of the clouds. Then I have sent the image back to gimp, changed the precision of the image to “16 bit integer” and exported to TIFF. This gives me a perfectly usable tiff image:
On the other hand, the 32-bit floating point TIFF file that is created if I export the Gimp image without changing the precision to “16 bit integer” cannot be opened by the default image viewer of my Mint 17 distribution.
I was expecting an option that lets you choose the precision of the TIFF file being exported, independently of the precision set in the Gimp image, but I could not find it…
Exporting to Jpeg gives a correct output.
I suspect that the artefacts you see are due to the way your image viewer interprets pixels whose 32-bits floating point values are exceeding 1.0, since they are only limited to bright areas. However, the image data itself is correct, since the floating-point TIFF file can be re-opened correctly in GIMP.