Photomicrographer James E. Hayden, RBP has been a consistent winner of the Small World competition for many years. Featured below is a photomicrograph of a male roundworm specimen taken with multiple exposure darkfield illumination with the assistance of a crossed red/blue filter.

Male Ostertagia ostertagi (Roundworm) Original Magnification: 46.7x Specimen: Unstained wet mount Technique: Multiple exposure darkfield with crossed red/blue filter

If the specimen has no inherent color to start with, refraction of the white light will only provide levels of gray. Any color must be added with colored filters. In this example, as with the next two images, the filter used was a circular piece of acetate divided into four quarters. The colors of each quarter alternate blue and red. When placed over the field diaphragm during darkfield, the white light that illuminates the specimen is replaced with the colored light. Because of the arrangement of the colors, structures that are oriented in one direction refract the blue light, while structures oriented 90 degrees to that refract the red light. Where there is a chaotic orientation, the colors combine. The result can be quite striking as seen with this male roundworm. Additionally, the use of darkfield allowed me to easily use multiple exposure techniques to get both ends of the worm in one image. Although images could have been combined in the computer, at the time these were taken, it was not an option.