Ask a full-frame photographer to choose just one prime lens and it would often be a 50mm, thanks to its entirely natural viewing perspective. Taking the 2x crop factor of Micro Four Thirds cameras into account, the Olympus M.ZUIKO DIGITAL 25mm f/1.8 gives the same field of view. Sure, f/1.2 and f/1.4 lenses enable faster shutter speeds under low lighting conditions, and a tighter depth of field, but f/1.8 is also a favorite for keeping a reign on size, weight and expense.
Olympus M.Zuiko 25mm f/1.8: Specifications
Mount: Micro Four Thirds
Lens construction: 9 elements in 7 groups
Angle of view: 47 degrees
Diaphragm blades: 7
Minimum aperture: f/22
Minimum focusing distance: 0.24m
Maximum magnification ratio: 0.12x
Filter size: 46mm
Olympus M.Zuiko 25mm f/1.8: Key features
The size and weight of this lens is among its key features. It measures just 58x42mm and weighs a mere 137g, making for a very discreet combination with small form-factor MFT camera bodies. The modest f/1.8 aperture is a key ingredient in the downsized design. It’s two-thirds of a stop or a full stop slower than f/1.4 or f/1.2 lenses but most faster lenses are larger, heavier and around two or three times as expensive to buy.
Despite its relatively tiny build, the lens feels tough and well engineered. Indeed, it’s billed as a 'Premium' lens. It features MSC (Movie & Still Compatible) autofocus, which is quick for stills and enables smooth, virtually silent autofocus transitions when shooting movies. The electronically coupled manual focus ring is the only ‘large’ thing about the lens, making manual focusing comfortable and precise, with a very smooth action.
Unlike its sibling M.ZUIKO DIGITAL ED 75mm f/1.8, this one doesn’t feature any Extra-low Dispersion glass but it does have two aspherical glass elements. The seven-blade diaphragm maintains a fairly well rounded aperture when stopping down a little from f/1.8.
Olympus M.Zuiko 25mm f/1.8: Performance
Despite ‘only’ having an f/1.8 aperture, the lens delivers very smooth bokeh. Sharpness is thoroughly excellent, even when shooting wide-open, while color fringing is entirely negligible. Barrel distortion can be a little noticeable and slightly worse than we’re used to from most MFT lenses, which take advantage of automatic in-camera correction. Even so, overall performance and image quality are deeply satisfying.
Olympus M.Zuiko 25mm f/1.8: Lab results
We run a range of lab tests under controlled conditions, using the Imatest Master testing suite. Photos of test charts are taken across the range of apertures and zooms (where available), then analyzed for sharpness, distortion and chromatic aberrations.
We use Imatest SFR (spatial frequency response) charts and analysis software to plot lens resolution at the center of the image frame, corners and mid-point distances, across the range of aperture settings and, with zoom lenses, at four different focal lengths. The tests also measure distortion and color fringing (chromatic aberration).
Even wide-open at f/1.8, sharpness is exceptional across the entire image frame, right out to the extreme edges and corners. It only really drops off noticeably at the narrowest aperture of f/22, due to the normal effect of diffraction.
Both axial and lateral chromatic aberrations are absolutely negligible, the latter being hard to spot even at the corners of the frame.
The slight barrel distortion is unusual for an MFT lens, automatic in-camera correction normally all but eliminating any distortions.
Olympus M.Zuiko 25mm f/1.8: Verdict
Barely bigger than a pancake lens, this Olympus gives the same field of view as using a 50mm standard prime on a full-frame camera, along with a fast f/1.8 aperture. Available in black or shiny silver, it’s ideal as an unfeasibly compact and lightweight ‘nifty fifty’ for any Micro Four Thirds camera, taking full advantage of the 2x crop factor. Image quality and all-round performance are highly impressive, but it’s pretty pricey for an f/1.8 standard prime.