Identifying space-variant motion blurs is a very challenging task in blind blur identification research. This paper describes a novel method towards blind identification without deblurring. Based on the image gradients in the -channel component of a blurred color image, an elegant -motion blur constraint is proposed, which is a linear constraint for local motion blur parameters. It makes possible efficient blind identification of space-variant and even nonlinear motion blurs and the estimation of motion blur fields, without deblurring.