Does gimp have optical filter imitations?

[Ofnuts]

(12-27-2017, 12:23 AM)godek Wrote: As you can see it says 8bits at the top but it allows me to change it to 16 bits in the menu though.

Yes, but you have lost data... From the 14-bit sensor you image can have 16000 values per channel. When you load as 8-bit you truncate the small variations and only keep 256 values. Going back to 16 won't revive these data. To be more explicit, let's use decimal values: with you 14-bit sensor you have 16000 values (let's says 10000 to be decimal), it's a bit as if you used 4-digit decimal values from 0.0000 to 1.0000: 0.0000, 0.0001, 0.0002.... to 0.9999, 1.0000. With 8 bits, you have only 256 values (let's say 100 to be decimal) so you are using number with two digits; from 0.00, 0.01 to 0.99, 1.00. When you load your 14-bit image in 8-bit Gimp, a value such as 0.1234 is rounded to 0.12, as will 0.1200, 0,1175, 0.1245... And if you set Gimp to 16-bit mode all you get is empty decimals, you 0.12 becomes 0.1200 but the initial values 0.1200, 0,1175, 0.1245 have all become 0.1200 now. Of course, further processing can use these extra decimals to avoid round off errors, but the damage to the initial data is done.

(12-27-2017, 12:23 AM)godek Wrote: I selected 16 bit output as you see before I clicked on the gimp icon.
Nufraw is version 0.40-1

I get this error when I try exporting the image from nufraw to gimp but it doesn't keep the image from being loaded though.

I get this error when I import a 16bit tiff from nufraw into gimp.

It looks like this when loaded into gimp which is not what it looked like in nufraw.

Given the error message the output isn't unexpected. Two cases:

1) the Nufraw author explicitly states that Gimp 2.9 is explicitly supported (which would be kind of mandatory to load 16-bit images in Gimp): get in touch with the author to have the bug fixed in Nufraw
2) you have been told that Gimp will support 2.8 plugins for opening images: this is a Gimp bug: report the bug on http://bugzilla.gnome.org (but you'll still be limited to 8-bit when the image loads)

A Workaround is to use a separate demosaicing app (that can also be Nufraw) that exports a 16-bit TIFF, and then open that TIFF in Gimp. If the problem persists, the subject TIFF is a good clue to give to developers of both sides, to determine if the TIFF is actually invalid (Nufraw problem) or if Gimp has trouble loading TIFF files (Gimp problem).