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Mquartet is the best solution found to the design problem posed at the 1994 International Lens Design Conference. It is often used as a reference point for global optimization. The monochromatic quartet is the name given by organizer D.C. O'Shea, to a lens that was designed according to the rules of the 1990 International Lens Design Conference contest. The lens was specified according to the requirement that it be the best design having a focal length of 100mm, a speed of f/3, and a field of 15 degrees, using four elements of BK7 glass. Of the 44 designs submitted, the top five were essentially the same (three were designed using OSLO), and it is speculated that this design is the global solution to the problem as stated. Since then, global optimization algorithms have often been tested to ensure that they find this solution.