Olympus M.Zuiko ED 25mm f/1.2 PRO Review

This site contains a few tests for MTF50, light dropoff, chromatic aberration and bokeh that I ran on the Olympus M.Zuiko ED 25mm f/1.2 PRO lens compared to the Panasonic Leica DG Summilux 25mm f/1.4.

The Olympus 25mm f/1.2 lens is bigger, heavier and considerably more expensive than the Panasonic 25mm f/1.4. Does the Olympus lens with 1/3 stop greater aperture significantly outperform the Panasonic lens in image quality?

MTF50 and Light Dropoff Results

MTF50 is one parameter used to assess image sharpness produced by photographic lenses and cameras. MTF50 performance was determined using Imatest Master v. 3.7 as described using a SFRplus Chart. A 13 region, center-weighted MTF50 value is posted below as well as center, midzonal, and corners lens performance. Regions of analysis on the SFRplus chart are described HERE. Light dropoff was also calculated using Imatest as described. Click on the images to see larger image files.

Center-Weighted Average MTF50	Light Dropoff (Vignetting)
MTF50 Data at 25mm for Center, Midzone and Corners Olympus M.Zuiko ED 25mm f/1.2 PRO lens	MTF50 Data at 25mm for Center, Midzone and Corners Panasonic Leica 25mm f/1.4 lens .

Chromatic Aberration and Geometric Distortion
Neither the Panasonic 25mm f/1.4 nor the Olympus 25mm f/1.2 have significant chromatic aberrations (i.e., greater than 0.04 area % in Imatest) or significant geometric distortion.

Test Photographs at 25mm with Mannequin Head Target with Bokeh Test Background
A number of lens design characteristics influence the quality of out of focus blur (online references: Merklinger , van Walree and Atkins) including aperture (both f/stop setting and maximal lens opening size), aperture iris shape, and degree of spherical aberration correction. In this test for each lens, the aperture was selected to bring both eyes into focus, and the qualities of the background were evaluated. The micro four thirds lens images were taken with a Panasonic Lumix GX7.

Olympus M.Zuiko ED 25mm f/1.2 @ f/8 Mannequin Head Target with Bokeh Test Background The mannequin is 6 feet in front of the background. The camera is 4.5 feet from the mannequin head. The focus point is the mannequin right eye. Click on image for target detail. There is text and a USAF1951 test pattern in the background as well as monolights and sequins on the paper for out of focus specular light images. The test determines whether both eyes are in focus as well as other head detail. The test also determines whether even blur discs are created from the specular light in the background on paper and whether the text is attractively blurred. The diaphragm aperture pattern shows in the image of the out of focus point light source. This image was taken while the scene was illuminated with a mixture of tungsten modeling lights and indirect sunlight through a skylight panel.

Olympus M.Zuiko ED 25mm f/1.2 @ f/1.2 Both eyes are in focus, and there is excellent background blurring with evenly blurred specular light discs in the background. Light drop off contributes to noticeable vignetting.

Panasonic 25mm f/1.4 @ f/1.4 Both eyes are in focus, and there is excellent background blurring. The out of focus specular light discs have outer bright rings suggesting that there may be slight over correction of spherical aberration. Light drop off contributes to noticeable vignetting. For comparison: f/2.0; f/2.8

Olympus M.Zuiko ED 25mm f/1.2 @ f/1.4 There is even more blurring of the text background compared to the Panasonic lens image at f/1.4. The out of focus specular light discs are larger and more evenly illuminated than those in the image produced by the Panasonic lens at f/1.4. The Olympus lens has higher quality bokeh. For comparison: f/2.0; f/2.8

Summary Points for Olympus M.Zuiko ED 25mm f/1.2 PRO lens
MTF50:
The Olympus 25mm f/1.2 lens has better MTF50 performance at f/1.2 and f/1.4 than the Panasonic 25mm lens has at f/1.4. The Olympus lens has a plateau of very good MTF50 performance between f/1.2 and f/2.8 and overall very good corner image MTF50 values. Center-weighted MTF50 performance is higher in the Panasonic f/1.4 lens between f2.8 and f5.6 than that of the Olympus f/1.2 lens. MTF50 performance in the corners and mid-zone field at f/1.4 and f/2 is significantly lower in the Panasonic lens than in the Olympus lens.

Light dropoff:
Both the Olympus and the Panasonic lenses have significant vignetting at their widest aperture that is partially resolved by stopping the lens down. Vignetting is greater in the Olympus lens. This vignetting can be corrected by processing RAW images.

Distortion and Chromatic Aberration:
There is no significant chromatic aberration or geometric distortion produced by either lens.

Bokeh:
The Olympus 25mm f/1.2 lens produces beautiful out of focus blur in the background with evenly illuminated specular light discs at f/1.2 and f/1.4. The quality of background blurring is noticeably better than that produced by the Panasonic 25mm f/1.4 lens when the lenses are compared at f/1.4. At f/2 and f/2.8, bokeh produced by the two lenses is very similar. The Pansonic lens produces excellent quality bokeh from f/1.4 onward.

Conclusion for the Olympus M.Zuiko ED 25mm f/1.2 PRO lens

The Olympus M.Zuiko ED 25mm f/1.2 PRO is a very high quality lens designed to be shot wide open for portrait photography with little diminution of image quality (e.g., MTF50) from f/2.8 to f/1.2 other than vignetting and shallowing of depth of field. Bokeh produced by the lens at f/1.2 and f/1.4 is exceptionally good with very even illumination of out of focus specular light. Image sharpness is very good across the field at wide aperture including in the corners. Image sharpness peaks between f/4 and f/5.6.

So does the Olympus 25mm f/1.2 lens with 1/3 stop greater aperture significantly outperform the Panasonic 25mm f/1.4 lens in image quality? The answer is YES and NO. Yes, the Olympus lens provides outstanding sharpness and bokeh at f/1.2 and f/1.4 and can create beautiful isolation and clarity of a portrait subject with a diffusely blurred background. However, from f/2.0 to f/5.6, the imaging advantage of the Olympus diminishes, and the Panasonic 25mm f/1.4 outperforms the Olympus lens in MTF50. Bokeh produced by the Panasonic lens is excellent. Both lenses have major strengths. The deciding question at purchase time is: Does the photographer (or videographer) need outstanding optical performance at f/1.2 and f/1.4?

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posted 26 October, 2016, updated 28 October, 2016
© 2016, William L. Castleman