Olympus 25mm f/2.8 Zuiko Digital

(From Olympus lens literature) The Olympus Zuiko Digital 25mm ƒ/2.8 is a thin, lightweight single-focus standard pancake-type lens. The lens has an overall length of 23.5mm. When combined with E-410 or E-420, the total length including the camera body and lens is only 76.5mm. The result is an easy-to-store, easy-to-carry camera system with go-anywhere portability.

SLRgear Review
June 9, 2008
by Andrew Alexander

The Olympus 25mm ƒ/2.8 Zuiko Digital is a fixed-focal length ''pancake'' lens, and probably the smallest that Olympus produces. A pancake lens is typically constructed with the fewest number of lens elements possible, and in this case the 25mm is no exception, with just 5 lens elements in four groups.

Released in 2008, the 25mm ƒ/2.8 Zuiko provides an effective field of view of 50mm when mounted on Olympus dSLR cameras using the 4/3 standard. The lens takes 43mm filters and has a lens hood as an optional accessory. The lens is available now for approximately $250.

Sharpness
The 25mm ƒ/2.8 provides very sharp results at what would be the typically most-used apertures for this lens: between ƒ/2.8 and ƒ/11. At these apertures we see no more than 1.5 blur units at any point. Set to ƒ/2.8 there is some evidence of uneven sharpness, though you have to look fairly close to see it.

Performance for sharpness is tuned well to the wider end of the aperture spectrum, and by ƒ/4 the lens is as good as it gets, which is almost tack-sharp. This performance is maintained between ƒ/5.6-ƒ/8, and while diffraction limiting starts to set in at ƒ/11, quality does not suffer overly. At ƒ/16 the lens hits 2 blur units, and 3 units at ƒ/22.

Overall, very impressive results for sharpness, and while there is an uneven quality to the results at ƒ/2.8 statistically it really doesn't make a practical difference. If absolute optical quality is your objective, you can achieve it at ƒ/4, but I think you would be hard-pressed to notice the difference shooting at ƒ/2.8.

Chromatic Aberration
The resistance of the lens to chromatic aberration is at its best when used at wider apertures, achieving its best results shot wide open at ƒ/2.8. At this point chromatic aberration is evident only at 3/100ths of a percent of frame height on average, and 4/100ths in the corners. This performance degrades as the lens is stopped down, reaching its ''worst'' results for chromatic aberration at ƒ/16 and ƒ/22 (5/100ths and 7/100ths respectively).

Shading (''Vignetting'')
While sharpness and chromatic aberration show good performance at wider apertures, corner shading is more evident. At ƒ/2.8 the corners are 2/3 of a stop darker than the center, and at ƒ/4 this corner shading drops to a just under a half-stop; by ƒ/5.6 and smaller the corner shading is a quarter-stop or less.

Distortion
Distortion is fairly high for the intended purpose of this lens; of the barrel variety, distortion reaches 0.3% on average and 0.6% in the corners. The distortion is linear and uncomplicated, meaning it is is fairly easy to correct in image post-processing software.

Autofocus Operation
The 25mm ƒ/2.8 focuses very quickly and silently. The Olympus focusing system is electronically controlled, so you can enable a full-time manual override option by selecting the ''AF + MF'' option in the camera menu. This allows you to override autofocus results at any time by just turning the focus ring.

Macro
With a magnification ratio of 0.19x, there are better choices for macro work. That said, the lens has a minimum close-focusing distance of 20cm (7.9 inches), meaning that your subject can be as close as 4 1/2 inches from the front of the lens.

Build Quality and Handling
The 25mm ƒ/2.8 is a typical example of a pancake lens - very small. Rob, one of our laboratory technicians who tested this lens, commented that the lens is so small, you could probably fit it attached to an E510 into your coat pocket. Weight, or lack thereof, is a big plus - the lens weighs only 95 grams (just over 3 ounces).

Because the lens is so small it lacks the room for features that some users may not miss - notably, distance and depth-of-field scales. Switching from automatic to manual focus is done through a camera menu, so there is also an absence of a dedicated switch to perform this function. The lens feels very nice and solid, perhaps because of the lack of ornamentation. The lens mount is metal, and the filter mount is plastic. A hood isn't supplied with the lens, but is marked as an optional accessory from Olympus.

The only feature of any note on the lens is the manual focus ring. The ring is a 1/4-inch wide, compose of a slightly raised, ribbed rubber that provides a very nice grip for manual focusing. We were very surprised at the amount of travel available in the ring for manual focusing - a whopping 510 degrees! This translates into a full 360 turn, plus another 150 degrees (almost a half-turn) of travel to go from infinity to close focus. Ring travel is important for manual focus operations as it gives the user a higher degree of accuracy between focus points, however, it could be argued that with this particular lens such a large amount of travel isn't strictly necessary. It's likely that this lens will be used mostly with autofocus, and it's nice to have more ring travel rather than less.

The 25mm won't mount on older film bodies, as it doesn't fit the lens mount, thus, we don't need to worry about potential vignetting issues. Even if it did, there would be no way to focus it since the newer Olympus lenses use a fly-by-wire focus mechanism.

NOTE: Olympus advises that if you are using the E300 camera, its Firmware must be version 1.3 or higher to use this lens.

Alternatives

Olympus 14-54mm ƒ/2.8-3.5 Zuiko Digital ~$420
At 25mm, this lens produces comparable or better results than the 25mm ƒ/2.8 pancake. Images are as sharp, have much better tolerance to chromatic aberration, comparable corner shading, and much better distortion. Maximum aperture at 25mm is ƒ/3.1, though. It costs more, but it offers a much wider range of focal lengths, as it's a zoom lens.

Panasonic 25mm ƒ/1.4 ASPH Leica D SUMMILUX ~$800
The Panasonic offering is five times heavier, and significantly more expensive, but it offers a full two stops more speed than the Olympus. The optical design is much more complex. Not yet tested.

Sigma 24mm ƒ/1.8 EX DG Aspherical Macro ~$330
Available in the 4/3 mount, the Sigma 24mm is almost the same focal length, slightly faster (1 1/3 stops), and offers a macro mode of 0.37x magnification. We haven't yet tested this lens, but anecdotally focus speed is slower with the non-HSM design.

Sigma 30mm ƒ/1.4 EX DC HSM ~$430
The Sigma 30mm ƒ/1.4 is much softer wide open at ƒ/1.4; the Olympus is sharper at ƒ/2.8. The Sigma is heavier, and uses 8 aperture blades instead of 7. Chromatic aberration results are slightly worse, but distortion and corner shading are comparable.

Conclusion
We found the 25mm a very fun lens to use: when mounted on the E510, it made a very compact package that almost felt like a large point-and-shoot camera. The lens performed extremely well in our optical tests, and with a very reasonable price, we have no hesitation in recommending it to Olympus users.

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.