The lens usually has two measurements of F stop or aperture: the maximum aperture (minimum F stop) when the lens is fully open and the minimum aperture (maximum F stop) just before the lens completely closes. The F stop has a number of effects upon the final image. A low minimum F stop will mean the lens can pass more light in dark condition, allowing the camera to produce a better image at night. A high maximum F stop may be necessary where there is a very high level of light or reflection. This will prevent the camera from "whiting out" and maintain constant video level. All Computar auto iris lenses are supplied with Neutral Density spot filters to increase the maximum F stop. The F stop also directly affects the depth of field.