Hello, For your READ_TIFF command, "read_tiff(myfile, r, g, b)", this assumes that "myfile" contains a color palette (color table). If that is not the case the R, G and B will not be defined. You can determine if your TIFF file has a color palette with a commands like: !null = query_tiff(myfile, info) print, info.has_palette ? 'Has a color palette.' : 'No color palette.' Here's an example using the "examples.tif" file which is included with an IDL installation: IDL> file = filepath('examples.tif',subdir=['examples','data']) IDL> print, file C:\Program Files\Exelis\IDL85\examples\data\examples.tif IDL> print, query_tiff(file, info) 1 IDL> print, info.has_palette ? 'Has a color palette.' : 'No color palette.' Has a color palette. IDL> img = read_tiff(file, r, g, b) % Loaded DLM: TIFF. IDL> help, r, g, b R BYTE = Array[256] G BYTE = Array[256] B BYTE = Array[256] IDL> device, decomposed=0 IDL> tvlct, r, g, b IDL> help, img IMG BYTE = Array[375, 150] IDL> window, xsize=375, ysize=150 IDL> tv, img, /order Or with function graphics, just issue the commands: file = filepath('examples.tif',subdir=['examples','data']) img = image(file) I hope this will be helpful. Regards,