Grayscale in 16 bit TIFF highly distorted - Printable Version +- Gimp-Forum.net (https://www.gimp-forum.net) +-- Forum: GIMP (https://www.gimp-forum.net/Forum-GIMP) +--- Forum: General questions (https://www.gimp-forum.net/Forum-General-questions) +--- Thread: Grayscale in 16 bit TIFF highly distorted (/Thread-Grayscale-in-16-bit-TIFF-highly-distorted)

Grayscale in 16 bit TIFF highly distorted - briligg - 05-30-2018 I have been working with a very large TIFF from the USGS of the lunar surface. It is an elevation map that indicates height as a shade of gray. It is too large for me to open directly, so i've been processing it with Image Magick, to crop, reduce size, or change format. Every version generated has had the same distortion of the grayscale. There are no midtones, everything is pushed to the white and black ends of the scale. It's like the histogram was pushed to one end and wrapped around to the other end.  I am inquiring on the Image Magick forum as to how i might correct this. But it occurred to me, that maybe this is to do with a profile for grayscale embedded with the file, and that if i could convert it to a different profile, it would all be fixed.  Is that a possibility? RE: Grayscale in 16 bit TIFF highly distorted - Ofnuts - 05-31-2018 The histogram you see is gamma-corrected (second icon to the right of Reset channel). Use the linear-light histogram (left-most icon in same group). This said I don't see much medium gray in what you show. RE: Grayscale in 16 bit TIFF highly distorted - rich2005 - 05-31-2018 Is it from this page? https://astrogeology.usgs.gov/search/details/Moon/LRO/LOLA/Lunar_LRO_LOLA_Global_LDEM_118m_Mar2014/cub 8 GB download so not for me, but are the tiles you created supposed to look like the sample jpg, but coming out as if threshold has been applied. https://i.imgur.com/oa4JM67.jpg While IM is probably the best tool, there might be other ways to tile the big image and apply corrections. Do you need it 16 bit?