Methods and apparatus are provided for computing focus information prior to scanning microscope slides with a line scan camera. The methods include a point-focus procedure that works by moving the slide to the desired measurement location, moving the objective lens through a predefined set of height values, acquiring imagery data at each height, and determining the height of maximum contrast. The methods also include a ribbon-focus procedure whereby imagery data are acquired continuously, while the slide and objective lens are in motion. Both methods may be applied with either a static or a dynamic implementation.