 <p>I think with the .tif format you have to use the command </p> <pre><code>[X,map] = imread('imagename.tif') newmap = rgb2gray(map) imshow(X,newmap) </code></pre> <p>Link to online Matlab help where's this exact example: <a href="http://it.mathworks.com/help/matlab/ref/rgb2gray.html" rel="nofollow">RGB to gray</a></p>