Abstract: A computer controlled photoplotter includes a row of LED's (light emitting diodes) mounted to a light head positioned parallel to the film width. The light head is part of a light head assembly which is moved parallel to the film length. At the end of each pass the lighthead is indexed widthwise a short distance. During each lengthwise pass the LED's are illuminated at appropriate positions to expose the film at those positions according to the image being plotted. The computer receives the image data in vector form--typically end points, widths of lines and particular shapes are provided. The vector data is rasterized for only those columnar positions underlying the LED's for each pass. That is, columnar rasterization is accomplished by determining the desired state of each LED at each position along a columnar path.