Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for object detection are disclosed. Methods can include, for each of a plurality of locations in one or more positive images, image filters are identified, each image filter representing visual features of a location in a positive image (e.g., an image that includes a particular object). Positive location feature scores and negative location feature scores are determined for locations within images. A positive location feature score is based on a similarity between the image filter and feature values for a positive image. A negative location feature score is determined based on a similarity between the image filter and feature values for a negative image. A distinctive location is identified based on the positive and negative location feature scores, and distinguishing feature values for identifying the particular object are identified for the distinctive location.