The Olympus Zuiko Digital 25mm 1:2.8 was announced in March 2008, alongside the Olympus E-420 DSLR. It’s a standard Four Thirds lens which means it will work on any Four Thirds body, including those from Olympus, Panasonic and Leica, although it’s physically best-matched to the smaller models like the Olympus E-4xx and E-5xx series.
Affectionately known as a pancake lens, the Zuiko Digital 25mm is very thin: indeed it’s just 23.5mm thick and weighs only 95g. When fitted to a smaller DSLR like the Olympus E-420, the result is a highly portable kit that’ll squeeze into larger pockets and has a total operating weight including battery of 521g.
With the Four Thirds field-reduction of 2x, the Zuiko Digital 25mm offers an equivalent coverage of 50mm. In full-frame and 35mm film terms, this makes it a ‘standard’ lens for general purpose use. In the past, 50mm lenses were the standard used by all 35mm film SLRs and while most modern photographers have become used to zoom lenses, it’s surprising how flexible a 50mm can be in practice. It’s just about wide enough to grab a decent landscape or interior shot, while long enough to attempt respectable portraits. Read the whole article here. You can buy the lens here