HELIOPAN close-up lenses are used when the closest focusing distance needs to be extended into the close-up area These convex lenses (plus) shorten the focal length at the same focus setting. They are supplied in the most popular screw-in, push-on, drop-in and bayonet sizes. Close-up lenses can be used in combination. To avoid edge unhappiness, one should stop down to at least F 5 6 or F 8 No exposure correction is necessary. The following strengths are available: NIL 1.0, NL 2 0, NL 3 0, NL 4 0.