Panasonic DG Vario-Summilux 10-25mm f/1.7 ASPH. lens (H-X1025)

      Photo Review 9.0


      In summary

      The Panasonic DG Vario-Summilux 10-25mm f/1.7 ASPH (H-X1025) is a fast, high-performance lens that will attract the attention of serious M4/3 and Sony E-mount photographers.

      Videographers should find this lens especially useful since its wide zoom range can cover angles of view from ultra-wide to medium/standard focal length quickly without requiring them to change lenses. For many, this lens could replace up to four prime lenses.


      Full review

      Announced at the end of May, the Leica-branded Panasonic DG Vario-Summilux 10-25mm f/1.7 ASPH (H-X1025) lens is a fast zoom lens for M4/3 cameras that covers angles of view equivalent to 20-50mm in 35mm format. Constructed mainly from magnesium alloy, it boasts weatherproof sealing, internal focusing and a clutch mechanism for quickly switching between auto and manual focus. We reviewed this lens on the new Lumix DC-G95 camera.

      Angled view of the new DG Vario-Summilux 10-25mm f/1.7 ASPH (H-X1025) lens. (Source: Panasonic.)

      The optical design of this lens consists of  17 elements in 12 groups, including three aspherical elements to suppress spherical aberration and distortion  while four ED (Extra-low Dispersion) lenses and one ultra high-refractive index element combine to control chromatic aberrations and colour fringing. These elements are arranged to  minimise image shifts during zooming. The diagram below shows how they are positioned.

      The optical design of the DG Vario-Summilux 10-25mm f/1.7 ASPH (H-X1025) lens showing the positions of the exotic elements. (Source: Panasonic.)

      The lens includes a a focus clutch mechanism for instant AF/MF switching and accurate manual focusing. Its stepping motor sensor drive is capable of operating at up to 240 fps, which when combined with internal focusing delivers fast, smooth and quiet autofocusing for shooting stills and video clips.

      Stabilisation is not included and may be unnecessary in such a fast, wide-to-standard angle lens. The G95 camera used for our tests includes 5-axis sensor-shift stabilisation that claimed up to five stop shake correction.

      The aperture ring is de-clicked to provide seamless focus transitions when shooting video. A rounded nine-blade diaphragm imparts a smooth and pleasing bokeh quality.

      Who’s it For?
      The high price tag for this lens will probably confine it to professional users, especially wedding and corporate events shooters who record both video and stills. The 10-25mm range, equivalent to 20-50mm in 35mm format,  enables users to move from an ultra-wide to a ‘standard’ focal length quickly without having to change lenses.

      The fast, f/1.7 maximum aperture is useful for low-light photography and videography, while the silent inner focus drive system will be valuable when recording movie clips. Video shooters will also benefit from the ability to de-click the aperture ring for silent depth of field control.

      This lens is designed to be free of focus breathing (slight changes in focal length as focus is adjusted), which can be detrimental when recording movie clips and unsettling for subsequent viewers of the footage. It also confirms Panasonic’s on-going commitment to the M4/3 system.

      Build and Ergonomics
      The fast optics make this lens relatively large and heavy, although Panasonic has minimised weight by using magnesium alloy for the lens barrels. The supplied lens hood and end caps are made from solid black polycarbonate and attach to the lens with bayonet fittings. A low-gloss finish gives the lens a ‘quality’ look.

      The front section of the lens is approximately 17 mm deep and surrounds (and is joined to) the inner barrel. This section of the lens includes the bayonet fitting for the petal-shaped lens hood as well as a small white index dot that is aligned with the red lens fitting mark near the mounting plate.

      Nine millimetres behind the leading edge of the outer barrel is the aperture ring, which carries engraved settings that range from f/1.7 to the minimum aperture of f/16, with numerical identifiers at one-stop interval and one-third stop marks between them.  A red ‘A’ mark to the left of the f/1.7 mark indicates the auto aperture setting, which enables apertures to be set from the camera. This ring turns smoothly as the aperture is changed, allowing subtle adjustments in exposure and depth of field.

      Roughly 3 mm behind the aperture ring is the focusing ring, which is approximately 14 mm wide and acts as a clutch mechanism. Pulling the ring back reveals manual distance settings in metres and feet, ranging from 0.28 metres (the closest focus) to infinity. Pushing the ring forward engages autofocus.

      Aft of the focusing ring lies the zoom ring, which is roughly 27 mm wide, with a 20 mm wide ridged band around the leading edge. The inner barrel of the lens extends by about 15 mm as the lens is zoomed from 14mm (where it is shortest) to 25mm. The barrel extension at 10mm is approximately 5mm.

      Behind the ridged band is a smooth strip that carries the engraved settings for the 10mm, 12mm, 14mm, 18mm and 25mm focal length positions. These line up against a white bar on the fixed section of the barrel rear of the zoom ring.

      The outer barrel slopes inwards to end in a 17 mm wide strip that carries the focal length range and focus distance information plus the red index dot for aligning the lens with the camera’s mount. A further 10 mm wide sloping section ends in the metal lens mount, which is surrounded by a rubber gasket.

      Eleven contact points inside the mount pass signals between the lens and the camera. The lens is supplied with the usual front and end caps plus a petal-shaped lens hood with a locking button and a soft storage bag.

      Our Imatest tests showed the review lens comfortably exceeded expectations for the 20.2-megapixel sensor in the Panasonic G95 camera we used for our tests. As expected, resolution was slightly higher near the centre of the frame but it was still above expectations close to the periphery, indicating excellent performance.

      We obtained the highest resolution with the 14mm focal length at the maximum aperture. However, although for the other focal lengths the maximum resolution was higher about a stop down from maximum aperture, centre resolution remained high at the 12mm, 18mm and 25mm focal lengths from f/1.7mm to about f/before tailing off gradually to about f/8, where diffraction began to take effect. Edge softening was evident with the 10mm focal length at apertures up to about f/2.8. The graph below shows the results of our tests.

      Lateral chromatic aberration was almost entirely within the ‘negligible’ band at all aperture and focal length settings, with only the smallest apertures at 18mm and 25mm edging into the ‘low’ band. In the graph of our results below, the red line marks the border between negligible and low CA.

      No coloured fringing was observed in uncorrected files from our test shots, confirming that chromatic aberration is a minor issue with this lens. All Panasonic cameras provide internal corrections for JPEGs.

      Backlit subjects were handled quite well, although the lens was a little flare-prone at times. Slight veiling flare could affect images when a bright light source was just outside the frame but we found no instances of flare artefacts, even when the light source was shining directly into the camera.

      Since Panasonic cameras apply corrections to JPEG files when they are produced, we had to examine RW2.RAW files to detect both vignetting and rectilinear distortions. We found slight vignetting in uncorrected files at f/1.7 at all focal lengths, with the most visible vignetting occurring at the longer focal lengths.  It reduced quite quickly  as the lens was stopped down and was effectively invisible by f/2.2.

      Distortion can be tricky to measure with ultra-wide-angle lenses because even a slight tilt can introduce perspective distortion. Examination of uncorrected files showed this lens to be almost distortion-free.

      Barrel distortion could just be detected at 10mm and slight pincushion distortion at 25mm with virtually no distortion in between. Both are easy to correct when converting raw files into editable formats and they’re addressed during in-camera JPEG creation.

      Close-up shooting performance was aided by the ability of the lens to resolve centre-of-frame details, along with its minimum focus distance of 28 cm throughout the zoom range. At the 25mm position a magnification of 0.14x makes it possible to shoot close-ups of larger flowers and similar sized objects.

      Bokeh was a little choppy at the shorter focal lengths but smoother and more pleasing by 25mm. The f/1.7 maximum aperture produces nice blurring with low-contrast backgrounds, with bright highlights were rendered as little circles at shorter focal lengths. We found some outlining of highlights in shots with bright background elements but not enough to be a significant distraction.

      Autofocusing was quick and quiet and virtually silent. Focus accuracy was generally good, even in relatively low light levels. Manual focusing was much as you’d expect from a focus-by-wire lens, which has no mechanical coupling with the camera.


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      Picture angle: 94 to 47 degrees
      Minimum aperture: f/16
      Lens construction:17 elements in 12 groups (including  3 aspherical, 4 ED and 1 UHR elements)
      Lens mounts: Micro Four Thirds
      Diaphragm Blades: 9 (circular aperture)
      Focus drive: Stepping motor
      Stabilisation: No
      Minimum focus: 28 cm
      Maximum magnification: 0.14x
      Filter size: 77 mm
      Dimensions (Diameter x L): 87.6 x 128.0 mm
      Weight: 690 grams
      Standard Accessories: Lens front and end caps, lens hood, storage bag

      Distributor: Panasonic Australia, Ph. 132 600;



      Based on JPEG files from the Lumix G95 camera.



      Vignetting at 10mm, f/1.7.

      Vignetting at 12mm, f/1.7.

      Vignetting at 14mm, f/1.7.

      Vignetting at 18mm, f/1.7.

      Vignetting at 25mm, f/1.7.

      Rectilinear distortion at 10mm.

      Rectilinear distortion at 12mm.

      Rectilinear distortion at 14mm.

      Rectilinear distortion at 18mm.

      Rectilinear distortion at 25mm.

      10mm focal length, ISO 200, 1/400 second at f/11.

      12mm focal length, ISO 200, 1/200 second at f/11.

      14mm focal length, ISO 200, 1/320 second at f/11.

      18mm focal length, ISO 200, 1/320 second at f/11.

      25mm focal length, ISO 200, 1/320 second at f/11.

      Close-up at 10mm focal length, ISO 200, 1/1600 second at f/1.7.

      Close-up at 25mm focal length, ISO 200, 1/1600 second at f/1.7.

      Angled shot showing characteristic wide-angle distortion; 10mm focal length, ISO 200, 1/30 second at f/8.

      The same subject, photographed with the 25mm focal length, ISO 200, 1/60 second at f/8.

      10mm focal length, ISO 200, 1/3 second at f/8.

      Crop from the above image enlarged to 100% to show edge details.

      25mm focal length, ISO 200, 1/6 second at f/8.

      Crop from the above image enlarged to 100% to show edge details.

      10mm focal length, ISO 200, 1/25 second at f/8.

      Stabilisation test; 10mm focal length, ISO 200, 1/2 second at f/5.6.

      Stabilisation test; 10mm focal length, ISO 200, 1/4 second at f/8.

      10mm focal length, ISO 200, 1/100 second at f/8.

      25mm focal length, ISO 200, 1/400 second at f/11.

      10mm focal length, ISO 200, 1/8 second at f/9.

      An example of using this lens for street photography; 25mm focal length, ISO 400, 1/125 second at f/7.1.

      Additional image samples can be found with our review of the Lumix G DC-GX95 camera.



      RRP: AU$2,799; US$1799

      • Build: 9.0
      • Handling: 8.9
      • Image quality: 9.0
      • Versatility: 8.8