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Design

The most striking aspect of the 25mm is inevitably its diminutive size; this is one of the smallest lenses currently available for any mount. Despite this it still feels pretty well-made, and with its metal mount and use of quality plastics for the lens barrel it's certainly a notch above certain manufacturers low-end, plastic mount 50mm primes. So whilst it's certainly ultra-lightweight, it doesn't feel at all insubstantial.

'Focus-by-wire' manual focus

The most unusual feature of this lens's operation is the focus-by-wire manual focus system, which drives the focusing group indirectly via the lens's autofocus motor (as opposed to the direct mechanical connection found in most lenses). As a consequence, the feel of the manual focus ring never changes, regardless of whether the camera is set to auto or manual focus, or the focus has reached the limits of its travel (either close or infinity), and this lack of tactile feedback can be a little disconcerting in some situations.

However the advantage of this system is that it does allow an extremely long focus travel, and a correspondingly high level of focus accuracy, in such a small lens. Now this isn't really going to help manual focus using the viewfinder of any Four Thirds DSLR bar the E-3 (probably the last camera this lens will be used on), but it does allow very accurate manual focusing in live view mode.

On the camera

The lens is a perfect match for Olympus's ultra-compact E-4x0 SLR bodies, on which it gives the most pocketable SLR/lens combination currently available; it's also equally at home on slightly larger cameras such as the E-5x0 series. The only external control is the manual focus ring, which falls naturally to hand when required.

Autofocus

Autofocus is driven by a micro motor in the lens body, which works just fine. It's pretty quiet in operation, although not quite as refined as ultrasonic-type motors. Focus speed and accuracy is dependent upon a number of variables, including the camera body used, subject contrast, and light levels; we found focusing to be generally fast and accurate under most conditions, and certainly adequate for the likely uses of the lens.

Lens body elements

The lens features the 'open standard' Four Thirds mount, currently compatible with dSLRs from Olympus and Panasonic. Communication with the camera is all-electronic, via the gold-plated contacts.

The lens mounts by aligning the red dot to that on the camera’s mount, and rotating clockwise to lock. A nice touch is the addition of moulded ribs on the side which provide a positive grip when changing lenses.

The thread is 43mm, which whilst not exactly common, will still accept plenty of currently available filters. It does not rotate on focusing, which will be welcome to filter users.

The screw-in metal cap, whilst suitably retro and in keeping with the slimline design philosophy, is possibly the least practical imaginable. Do yourself a favour and source a clip cap instead.

The manual focus ring is just 5mm wide, but extremely smooth and well-damped. The focus-by-wire internal focus system also allows a remarkably generous travel of about 400 degrees from infinity to 0.2m, and has sufficiently fine focusing steps to take full advantage.

The lens focuses by moving the entire optical assembly, with a maximum increase in length of just 5mm.

Reported aperture vs focal length

The lens allows apertures from F2.8 to F22 to be selected.

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