In 1966 the Pen EE (1961) and the Pen EES (1962) were slightly modified and became the Pen EE (EL) and Pen EES (EL) with a modification of the take-up spool to make film loading easier. EL stands for Easy Loading. You can only recognize them by a small label marked EL stuck on the front, or you can open them and look at the take-up spool. These EL cameras were discontinued two years later in 1968. The camera have a fully automatic exposure system and fixed focusing. It is a true point and shoot camera, and has a 28mm f/3.5 lens. The Pen EE family is easily recognized by the selenium meter window around the lens. The shutter speeds were 1/30 and 1/250 of a second. The shutter speed changed automatically according to light level, thus increasing the appropriate exposure range. A three-zone focus system was used to adjust the focal point. By using the half-frame format, Olympus was able to reduce both the weight and size of the Olympus Pen. It featured a simple rear-winding mechanism, a D-Zuiko lens for superior photographic quality, and an attractive design that also made the camera extremely easy to use. The Pen was a compact mix of innovative ideas that triggered the half-frame camera boom of the 1960s and 1970s. Cumulative sales of Pen Series cameras exceeded 17 million units.