The Pen series is a family of half-frame cameras made by Olympus from 1959 to the beginning of the 1980s, and from 2009. Aside from the Pen F series of half-frame SLRs, they are fixed-lens viewfinder cameras.
General context 
The original Pen was introduced in 1959. It was designed by Yoshihisa Maitani, and was the first half-frame camera produced in Japan. It was one of the smallest cameras to use 35mm film in regular 135 cassettes. It was thought to be as portable as a pen; thus the name. The idea was to be much copied by other Japanese makers.
A series of derivatives followed, some easier to use with the introduction of exposure automation, e.g. the Pen EE; others with a wider aperture lens and a manual meter, such as the Pen D.
In 1966 the arrival of the Rollei 35, a camera almost as compact but making normal 24×36 exposures, would announce the beginning of the end for the half-frame concept. However, Olympus went on producing the simpler models of the Pen family until at least 1983.
In the descriptions below, the focal lengths indicated do not give the same angle of view as for full-frame cameras: 30mm on the Pen is roughly equivalent to 45mm on a full-frame, and 28mm to a 40mm.
The Pen and Pen S 
The original Pen is a very compact half-frame camera, with just a viewfinder, no meter and fully manual settings. It has a 28mm f/3.5 Zuiko lens. Its shutter settings are 25, 50, 100, 200, B; its aperture range from 3.5 to 22. The back is removed completely for film loading and unloading.
The Pen S is almost the same camera, with the following shutter settings: 8, 15, 30, 60, 125, 250, B. It existed in two versions, with a 30mm f/2.8 lens or an 28mm f/3.5 lens.
The Pen D series 
The Pen D was a more expensive model, launched in 1962. It has a 32mm f/1.9 lens, a shutter going to 1/500 and an uncoupled selenium meter.
The Pen D2, launched in 1964, is the same model with an uncoupled CdS exposure meter replacing the selenium one.
The Pen D3, launched in 1965, is the same with a 32mm f/1.7 lens.
The Pen EE series 
The Pen EE was introduced in 1961 and was the amateur model, with fully automatic exposure 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 Pen EE.S, launched in 1962, is the same model with a 30mm f/2.8 and a focusing ring, made necessary by the wider aperture.
In 1966 the two cameras were slightly modified and became the Pen EE (EL) and Pen EE.S (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.
The Pen EE.2, produced from 1968 to 1977, is nearly the same as the Pen EE with the addition of a hot shoe.
The Pen EE.3, produced from 1973 to 1983, seems to be exactly the same camera.
The Pen EE.S2, produced from 1968 to 1971, is the same as the Pen EE.S with the addition of a hot shoe. EES-2's User Manual in English
The Pen EE.D, produced from 1967 to 1972, is a more expensive automated-exposure model, with a CdS meter, a 32mm f/1.7 lens and a hot shoe.
The Pen EF, launched in 1981, was the last Pen model. It is like the Pen EE.2 or Pen EE.3, but with a small built-in flash, and was only sold in black finish with white letterings.
The Pen Wide 
The Pen W or Pen Wide is a very rare variant of the Pen S model, with a wide-angle 25mm f/2.8 lens, equivalent to a 35mm in full format. It only exists in black finish, and has a cold flash shoe. It was only produced between 1964 and 1965, and today fetches high prices on the collectors' market.
The Pen EM 
The Pen EM, produced from 1965 to 1966, is a motorized Pen model. It has a 35mm f/2 lens, and a CdS exposure meter allowing automatic or manual exposure.
The PEN F, PEN FT, PEN FV 
The Pen Rapid models 
The Pen Rapid EE.S and Pen Rapid EE.D were variants of the Pen EE.S and Pen EE.D designed to accept the Agfa Rapid cassette instead of the regular 35mm cassette. They were both made from 1965 to 1966, and met very little success.
Digital PEN 
In June 2009, Olympus announced the PEN E-P1, an interchangeable lens Micro Four Thirds system digital camera which carries on in the PEN tradition. Its external design is clearly inspired by the traditional PEN series.
In January 2010, Olympus followed up the release of the E-P1 with the E-P2. For the most part, the E-P2 is identical to the E-P1 except it is available in all-black, and includes the ability to mount a high resolution electronic viewfinder. It also features two new art filters. The new port included for the electronic viewfinder can also be used for a microphone (not included). The suggested retail price at release was US$1099. The long awaited Olympus E-P3 was announced on June 30, 2011, to positive reviews.
On February 3, 2010, Olympus Corporation announced a third camera, the Olympus PEN E-PL1, L standing for Lite. The camera was a success, with the E-PL2 following almost a year later, and the E-PL3 arriving in Fall 2011.
On June 30, 2011, along with the E-PL3 and E-P3 announcements Olympus also announced the E-PM1, or "Pen Mini". The Mini was released with almost exactly the same specifications as the E-PL3 but in a slightly smaller and lighter package. The most notable difference, aside from price, being the lack of a tilting screen on the Mini.
- "E-P1". Olympus America. Retrieved 2009-06-16.
- "Olympus News Release:Introduction of OLYMPUS PEN E-P1 Micro Four Thirds interchangeable lens system camera". Olympus Imaging Corporation. Retrieved 2009-06-16.
- (English) Manual available in the Favorite Classics section of kyphoto.com
- (English) Olympus Pen EES-2 aperture repair
- (English) Olympus Pen at Marriott's World
- (English) Original Pen in Karl Blessing's website
- (French) Lionel's Olympus Pen EE-3 page at 35mm-compact.com
- (French) Pages at Sylvain Halgand's www.collection-appareils.com:
- Pen EE
- Pen EE-2
- Pen EES-2
- Pen EES
- (Japanese) Half-moon, a website fully devoted to the Pen and Pen F series