Standard Ring Lights are used for bright field illumination. This light is available in many different versions for applications that do not require longer working distances. The RL4 is also available in a washdown FDA compliant harsh environment version and is rated to IP68 standards. Spectrum Illumination Series RL/DF Ring Lights are used for bright field and dark field applications. Dark field lights are used to illuminate edges and surface defects. The four arrays on the RL/DF Lights can be adjusted from 0-90 degrees so that edges and features are illuminated properly. Because the RL/DF Light is adjustable the end user has greater flexibility in respect to working distance than other non adjustable dark field lighting products.