1. A method operational in an image feature detection device, comprising: generating a difference of scale space image by taking the difference between two different smoothened versions of an image; generating a normalized difference of scale space image by dividing the difference of scale space image by a third smoothened version of the image, where the third smoothened version of the image is as smooth or smoother than the smoothest of the two different smoothened versions of the image; modifying both the difference of scale space image and the normalized difference of scale space image by an illumination scaling function; and using the normalized difference of scale space image to detect one or more features for the image.