The Olympus Zuiko Digital 25mm F2.8 Pancake lens was announced in March 2008 to coincide with the E-420 ultra-compact DSLR, and occupies a unique position in the current market as the only fixed focal length ('prime') lens which is bundled as a kit with a camera body. In this it harks back to the 1980s heyday of the classic manual focus 35mm SLR, when cameras were supplied with 50mm F1.8 (or similar) lenses as standard, with which budding photographers learned their art. That 25mm focal length also corresponds directly to 50mm on the 35mm full-frame format, offering the same diagonal angle of view; this is therefore of the 'standard' class of lenses, offering none of the perspective distortion which is characteristic of wideangle or telephoto lenses.

The word 'Pancake' in the lens's title offers a clue to its most striking physical characteristic; it is extremely thin (just 24mm, or less than 1") and extremely light, making it the perfect complement to Olympus's E-4x0 class bodies as an (almost) pocketable, carry-anywhere solution, with all the speed and responsiveness of a DSLR coupled with image quality unmatched by any small-sensor compact digicam. However it's not the slimmest lens currently available; that honour falls to Pentax's almost unimaginably thin SMC-DA 40mm F2.8, at a mere 15mm. Other brands also have their own small primes such as 28mm F2.8s or 35mm F2s, but a Canon EOS 1000D fitted with a 28mm F2.8 lens will be fully 25mm/1" (i.e. 33%) thicker than an E-420 with a 25mm F2.8; this combination really is about as small as it gets for DSLRs.

The 25mm Pancake is also a rare example of a truly 'designed for digital' standard prime; aside from the Sigma 30mm F1.4 HSM, Panasonic's Leica-branded 25mm F1.4 for Four Thirds, and the aforementioned Pentax 40mm F2.8, such lenses have been most noticeable by their absence, with the major camera manufacturers preferring to concentrate on more consumer-friendly zooms instead. As such it's a welcome example of one of the smaller players offering a genuine alternative unmatched by the likes of Canon and Nikon; however the big question is whether this lens really offers something sufficiently different to capture the imagination of buyers.

Click here for our accompanying review of the Olympus E-420 digital SLR

Optical diagram

The lens designers at Olympus faced an unusual challenge in designing this lens, as the 25mm 'normal' focal length for Four Thirds is substantially shorter than the flange distance from the lens mount to the imager. This means that the lens has to employ a so-called 'retrofocal' design usually associated with wideangle lenses, as opposed to the highly corrected symmetric designs used by traditional 50mm primes. The diagram above illustrates the lens's optical layout, showing an asymmetric design with 5 elements in four groups, including an aspheric element at the rear. It also shows just how small the lens elements are in this design, the largest having a diameter of approximately 21mm.

Use of the Panasonic L10 as Four Thirds test body

We have chosen to use the Panasonic L10 as our standard test body for Four Thirds lenses purely because it gives the highest numbers in our resolution tests (which we believe is most likely due to it having a relatively weak anti-aliasing filter); this is intended simply to provide the fairest comparison to other manufacturers' systems. The samples gallery contains images shot with both the Panasonic L10 and the Olympus E-520.

Headline features

  • 25mm fixed focal length; F2.8 maximum aperture
  • Ultra-thin, lightweight design 
  • 'Focus by wire' manual focus system
  • Four Thirds mount for Olympus and Panasonic dSLRS

Angle of view

The picture below illustrates the lens's angle of view (see here for comparative shots using the Zuiko Digital 14-42mm F3.6-5.6):

25mm (50mm equivalent)

Olympus Zuiko Digital 25mm 1:2.8 Pancake specifications

Street price • US: $250
• UK: £159
Date introduced March 2008
Maximum format size Four Thirds
Focal length 25mm
35mm equivalent focal length 50mm
Diagonal angle of view 47°
Maximum aperture F2.8
Minimum aperture F22
Lens Construction

• 5 elements/ 4 groups
• 1 Aspherical element
Number of diaphragm blades

7
Minimum focus 0.2m
Maximum magnification

0.19x
AF motor type DC Micro motor
Focus method Unit focus
Image stabilization

No
Filter thread • 43mm
• Does not rotate on focus
Supplied accessories*

Front and rear caps
Optional accessories LH-43 lens hood
Weight 95g (3.4 oz)
Dimensions 64mm diameter x 23.5mm length
(2.5 x 0.9 in)
Lens Mount Four Thirds

* Supplied accessories may differ in each country or area