In summary
Panasonic’s 25mm f/1.7 ASPH is an excellent performer that is very keenly priced. If you’re looking for a fast standard prime lens for a Micro Four Thirds format camera, it comes highly recommended.
Comparatively small and light for its type and nicely construction (although not weatherproof), it can be used on both Panasonic and Olympus cameras. However the lack of internal stabilisation will restrict which Panasonic models it matches best (the GX8 is ideal since it has stabilisation built-in).
Full review
Panasonic’s recently-released Lumix G 25mm f/1.7 ASPH is a prime lens for Micro Four Thirds (M4/3) cameras that has a field of view equivalent to 50mm in 35mm format. This is roughly equivalent to normal human vision, which is why this focal length has been popular for many years. It’s not as fast as the Leica DG Noctiron 42.5mm f/1.2 lens, but its a far lower price and considerably smaller and lighter.
Side view of the Panasonic Lumix G 25mm f/1.7 ASPH. lens without the end caps and lens hood. (Source: Panasonic.)
The optical design comprises eight elements in seven groups and includes two aspherical lens elements plus one UHR (Ultra High Refractive) lens. The paired aspherical elements reduce chromatic and spherical aberrations while the UHR element helps to achieve even illumination, sharpness and clarity throughout the aperture range.
This diagram shows the positions of the exotic elements in the lens design. (Source: Panasonic.)
Autofocusing is driven by a stepping motor, which is fast, smooth and almost silent, making this lens suitable for recording movie clips. The seven-bladed iris diaphragm is rounded and closes to produce a circular aperture for smooth out-of-focus backgrounds when working with shallow depths of field.
This lens is not weatherproofed so care is needed when working in damp or dusty environments. It is supplied with front and end caps plus a generous cylindrical lens hood.
Who’s it For?
Most photographers like to have a 50mm equivalent lens in their kit bags becausethey can be used for many different subject types, from architecture to landscapes and even portraiture (particularly group shots). While this focal length is usually covered by kit zooms, having a faster lens will provide much better depth-of-field control.
Although it’s not designed for macro work, this lens will focus close enough to be used for taking photographs of larger flowers, small animals and pets. Provided it’s not taken into damp or dusty environments, this lens is a very portable, go-anywhere lens when you want an undistorted view of your subjects.
Build and Ergonomics
Although mostly fabricated from polycarbonate plastic, the 25mm f/1.7 ASPH. lens is well built and nicely finished in smooth matte black. Weighing only 125 grams, it’s no burden to carry and small enough to slip into a jacket pocket, even with the lens hood in place.
Fitting the lens hood is a bit of a hassle since you have to remove the decoration ring to reveal the bayonet attachment for the hood. (There’s potential to lose the decoration ring if you remove and re-fit the hood a lot.) We suggest leaving the hood in place most of the time and ‘parking’ the decoration ring somewhere safe at home. The hood can be reversed over the lens to save space when it’s not in use.
The front element of the lens is roughly 20 mm in diameter and very slightly recessed. The filter ring stands well proud of the front of the lens and accepts 46 mm filters. The lens cap clips firmly into this ring and isn’t easily detached accidentally. Internal focusing means the front of the lens doesn’t rotate, enabling angle-critical filters to be used.
The focusing ring is 21 mm wide and located just behind the bayonet mount for the lens hood. It is covered with a finely-ribbed grip band and rotates through 360 degrees. Manual focusing is ‘by wire’ (controlled electronically from the camera) with minimal tactile feedback.
There’s no distance scale and no additional controls on the lens. The only other items are the red reference dot for attaching the lens and Panasonic’s branding marks. The metal mounting plate clips securely onto the camera’s lens mount.
Performance
The review lens showed itself to be a stellar performer in the Imatest tests we carried out with the GX8 camera body. JPEG files from this camera came very close to meeting expectations for its 20-megapixel sensor at f/1.7, met expectations at f/2.2 and remained above expectations through to f/8, after which diffraction kicked in.
The highest resolution was measured at f/5, where it was almost 20% above expectations, which is excellent for JPEG files. Edge and corner softening were slight throughout the aperture range and became insignificant from f/5.6 onwards, as shown in the graph of our test results below.
Lateral chromatic aberration was well controlled and effectively negligible at all but the widest lens apertures. The graph below shows the result of our tests with the red line marking the border between ‘negligible’ and ‘low’ CA.
We found some vignetting in raw files from the GX8 at the widest aperture settings. It was also present in JPEGs captured with the camera’s Shading Compensation switched off. The effect was most noticeable at f/1.7 but barely visible by f/2.5. Switching on the Shading Compensation eliminates it from JPEGs; raw files are easily corrected in conversion software.
Distortion was effectively negligible in both uncorrected JPEGs and raw files. Here, too, in-camera corrections make this aberration a very minor concern.
Because of its wide maximum aperture, the quality of out-of-focus blurring is an important criterion when assessing this lens. When backgrounds were evenly lit, bokeh was very smooth and attractive. However, we found some choppiness and slight outlining when backgrounds contained bright highlights. Examples are shown below.
The review lens was relatively flare-resistant, retaining a high percentage of both colour depth and contrast in scenes when a bright light was included within the frame. We found traces of veiling flare in outdoor shots taken with the sun just outside the frame. But contrast and saturation were quite easy to adjust in a decent image editor.
Conclusion
Panasonic’s 25mm f/1.7 ASPH is an excellent performer that is very keenly priced. If you’re looking for a fast standard prime lens for a Micro Four Thirds format camera, it comes highly recommended.
Comparatively small and light for its type and nicely construction (although not weatherproof), it can be used on both Panasonic and Olympus cameras. However the lack of internal stabilisation will restrict which Panasonic models it matches best (the GX8 is ideal since it has stabilisation built-in).
Panasonic has set the price for this lens close to the current US MSRP (manufacturer’s suggested retail price), so you are better off buying this lens locally. Shop at a specialist retailer who can provide hands-on experience, advice and follow-up support for your purchase.
SPECS
Picture angle: 47 degrees
Minimum aperture: f/22
Lens construction: 8 elements in 7 groups (including two aspherical lens elements plus one UHR lens)
Lens mounts: Micro Four Thirds
Diaphragm Blades: 7 (circular aperture)
Focus drive: Internal stepping motor
Stabilisation: No
Minimum focus: 25 cm
Maximum magnification: Approx. 0.14x / 0.28x (35mm camera equivalent)
Filter size: 46 mm
Dimensions (Diameter x L): 60.8 x 52 mm
Weight: 125 grams
Standard Accessories: Lens cap, lens hood, lens rear cap, Decoration ring
TESTS
Based on JPEG files from the Panasonic DMC-GX8 camera.
SAMPLES
Vignetting at f/1.7.
Rectilinear distortion.
Close-up at f/1.7; ISO 200, 1/6400 second.
Close-up at f/2.5; ISO 200, 1/5000 second.
Close-up at f/5.6; ISO 200, 1/1000 second.
Close-up at f/11; ISO 200, 1/320 second.
Close-up at f/22; ISO 200, 1/125 second. Note the loss of sharpness due to diffraction.
ISO 400, 1/125 second at f/2.5.
Flare; ISO 640, 1/200 second at f/2.5.
Slight veiling flare; ISO 200, 1/500 second at f/5.6.
Differential focusing; ISO 200, 1/10,000 second at f/1.7.
ISO 800, 1/60 second at f/1.7.
ISO 400, 1/100 second at f/2.5.
ISO 200, 1/50 second at f/1.7.
ISO 800, 1/200 second at f/2.5.
ISO 800, 1/20 second at f/1.7.
ISO 1000, 1/25 second at f/2.
Rating
RRP: AU$299; US$249.99
- Build: 8.8
- Handling: 8.9
- Image quality: 9.0
- Versatility: 8.5