Camera Accessories

Released concurrently with the E-420 camera, the new Olympus Zuiko Digital 25mm f2.8 standard lens is a fast prime lens with 'pancake' styling. Less than 24mm thick, it makes a great companion to the E-420, providing a camera-plus-lens package that rivals many high-end digicams in size and weight. The 50mm effective focal length provides a near-natural visual field that is ideal for everyday photography.

Unlike the kit lenses offered with Olympus's entry-level DSLRs (which have plastic mounts), this lens has a solid metal mount. Designed to comply with the Four Thirds System standard, it consists of five elements arranged in four groups. Double-sided aspherical lens components are included to minimise the overall length of the lens while correcting major aberrations. All elements are coated to reduce flare and ghosting.

The diagram above shows the structure of the Zuiko Digital 25mm f2.8 lens and the position of the double-sided aspherical element.

The relatively low price of this lens reflects the amount of glass used in its construction since most of the elements appear to be small. However, this affects neither the speed of the lens, nor its performance. It's an excellent example of the original promise of the Four Thirds System to deliver cameras and lenses that are smaller, lighter and more cost-effective to manufacture than traditional 35mm lenses.

The seven-bladed diaphragm closes to a circular aperture for smooth and even-looking bokeh (background blur), while the maximum aperture of f/2.8 supports flash-free shooting in low light settings and provides good depth of field control. This lens can focus down to 20 cm (or 13 cm from the front of the lens), which isn't spectacular for close-ups but will deliver good results with suitable subjects.

Given the thickness of the lens, it's not surprising to find the focusing ring is also slender. However, a textured rubber coating provides a secure grip and allows precise focusing when the camera is in manual mode. No aperture ring is provided as apertures are controlled from the camera.

Supplied with the lens is a screw-on lens cap, made from aluminium. It's a neat idea - and certainly helps to keep overall size and weight down. However, in use, we found the lens cap difficult to remove and fit when we were on the move and it tended to cross-thread when fitted in a hurry.

The lens cap screws into the same thread as you use to fit filters and may cause some difficulties for photographers who like to keep a UV filter on their lenses. A clip-on lens cap would be quicker and easier all round.

Handling
The small size and narrow depth of this lens can make it difficult to mount on the camera although, once fitted, it's an excellent match to the E-420 body. However, the close proximity of the focusing ring to the camera's body makes adjusting focus manually a little tricky, especially for users with large hands or limited dexterity. It's probably best to use this lens in autofocus mode wherever possible.

Autofocusing was fast and accurate under all shooting conditions. Hunting was negligible, even in very low light levels.  No compromises were required for flash photography, thanks to the small size of the lens. 

Performance
Imatest showed slight edge softening throughout the aperture range, although resolution was generally quite high and the relationship between centre and edge resolution remained consistent at all apertures. The results of our Imatest tests, which also show the difference between JPEG and raw file resolution with the E-420 camera used for this review, are shown in the graph below.

Coloured fringing was found in shots taken in bright outdoor conditions but at a level that is unlikely to impact significantly on normal photography. Imatest showed lateral chromatic aberration to be low - but not negligible. The illustration below shows an example of the coloured fringing from one of our test shots.

Vignetting (edge darkening) was negligible at all apertures and we found little evidence of flare in contre-jour shots, although contrast appeared to be accentuated in some backlit shots. We observed slight barrel distortion in our Imatest test shots, although it would have a negligible effect on normal photography.

IMATEST GRAPHS

SAMPLE IMAGES

Close-up.

The image above shows the lens's ability to record detail and the absence of vignetting at the corners of the frame.

Focal length range: 25mm (= 50mm in 35mm format)
Picture angle: 47 degrees
Maximum aperture: f/2.8
Minimum aperture:  f/22
Lens construction: 5 elements in 4 groups. (Includes special double-sided aspherical lens element.)
Lens mount: Four Thirds System
Diaphragm Blades: 7 (circular diaphragm)
Minimum focus: 20 cm
Filter size:  43 mm
Dimensions (Diameter x L): 64 x 23.5 mm
Weight: 95 grams