Image transformation of tif image does not work
I found the way to create thumbnails of tif files. You have to change the function isImageManipulatable in the file /craft/app/helpers/ImageHelper.php:

public static function isImageManipulatable($extension)
{
    $extensions = array('jpg', 'jpeg', 'gif', 'png', 'wbmp', 'xbm');

   if (craft()-&gt;images-&gt;isImagick())
    {
        $extensions[] = 'svg';
    }

    return in_array(mb_strtolower($extension), $extensions);

}


To this:

public static function isImageManipulatable($extension)
{
    $extensions = array('jpg', 'jpeg', 'gif', 'png', 'wbmp', 'xbm');

   if (craft()-&gt;images-&gt;isImagick())
    {
        $extensions[] = 'svg';
        $extensions[] = 'tif';
    }

    return in_array(mb_strtolower($extension), $extensions);

}


I know, changing core code is not a real solution: i posted this change as a Craft feature request -> http://feedback.buildwithcraft.com/forums/285221-feature-requests/suggestions/8794456-better-support-of-image-types-in-image-transformat