LEICA DG Lens Story - The Quest for Changing Photography
LEICA DG SUMMILUX 12mm / F1.4 ASPH.
1. Development background
Making wide-angle lenses work well withmirrorless cameras
Owing to a short focal length, wide-angle lenses present challenges to optical performance. While making distortion, curvilinear deviation and astigmatism apparent, wide viewing angles also exacerbate other problems, such as chromatic aberration. The wider the diameter of the lens, the greater the challenges. Ideally, to maximize image quality, wide-angle lenses should be made with symmetrical optical lenses centered over the aperture.
In the case of single-lens reflex (SLR) cameras, however, the drop-down mirror makes it impossible to use symmetrical lenses in the optics for short focal length wide-angle lenses. To resolve this problem, retrofocus elements were introduced at the front of SLR system optics to extend the back-focus distance.* Ingenuity was also applied to compensate for the inferior rendering performance of asymmetric optics. By rethinking the optical arrangement, and by implementing floating focus, it was possible to obtain excellent performance with aspherical lenses using high-refractive index glass, ED glass, and elements made with other materials. Naturally, when extreme wide-angle, broad apertures, and superior performance are given priority, it becomes even more challenging to hit the sweet spot for factors such as size and cost performance.
* Back focus here refers to the distance from the imaging surface to the closest surface of the lens attached to the camera.
Digital technology enables through-the-lens viewing without the need for a mirror. Consequently, it is possible to reclaim the back-focus distance required by SLR optics. This greatly reduces the difficulty of designing excellence into the asymmetric optics required for superior extreme wide-angle lenses. While maintaining a compact form factor and minimizing weight, the ability to reclaim this space has enabled Leica to broaden the field of view, widen the aperture, and improve performance. It has become commercially viable to create a wide-angle lens with the well-balanced properties of a real photographic tool. By liberating internal space, mirrorless technology has enabled Leica, from corner to corner, to create a 12mm F1.4 lens that satisfies our stringent performance standards across the entire image. And, compared with similar models made by other makers for full-frame cameras, it provides superior performance with less size and less weight. In fact, the Leica super-wide for Micro Four Thirds has about half the bulk compared to full-frame 12 mm lenses.
2. Development aims
1. Target user
As the focal length of a wide-angle lens decreases, the angle of view increases and perspective greatly differs from the naked-eye view. This opens new dimensions of creativity. Extreme wide-angle lenses enable exploration of new forms of visual expression and allow photographers to shoot memorable photographs as they enjoy creating fresh images from interesting angles. This 12mm F1.4 lens has been developed to appeal to photographers who already use 25mm F1.4 lens or 12-35mm F2.8 lens, and who want to broaden their horizons and shoot different types of images.
15 sec, F5.0, ISO 200
2. Typical photographic subjects
Combines super-wide 24mm (equivalent) with F1.4 depth of field control The 12mm focal length is definitively wide angle. In fact, it is the entry point for extreme wide-angle shooting. With an angle of view that captures four times the area of a 25mm standard Micro Four Thirds wide-angle lens, the broad reach of the 12mm lens is often used for subjects such as landscapes, starry nights, and all-inclusive architectural shots of, for example, tall buildings or temples and churches. Photographers have long made use of the perspective distortion enabled by a 24mm* lens to create distinctive images taken from interesting camera angles. Because this bright Leica lens provides superb quality even fully open at F1.4, it is possible to place the main subject in context in dim interiors where there is no space to take a step backward. The wide aperture also enables emphasis by shooting close to the main subject and using selective focus to blur the background. This 12mm F1.4 lens offers both rich realism and uniquely photographic expression for all kinds of subject.
* 35mm camera equivalent.
1/2500 sec, F4.0, ISO 200
15 sec, F1.4, ISO 1250
© Bence Máté
4. Specification goals
Wide-aperture prime lens with superb capability and premier performance
In recent years, the 24mm* focal length has been implemented in many wide angle zoom and standard zoom lenses for full-frame cameras. Because 24mm* is so versatile and convenient, it has become a go-to lens for many users. This 12mm F1.4 offers the same 84-degree wide viewing angle and appeals to photographers who enjoy creating richly expressive photographs with compositions that stand out because of their perspective distortion. Creative options are also expanded by the wide F1.4 aperture plus the excellent color rendering and image quality. The high-quality exterior finish is also typically Leica, and the premium feel is apparent in the intuitive, smooth, satisfying focus control and aperture adjustment provided by the Leica Summilux 12mm F1.4.
* 35mm camera equivalent.
Technology to achieve picture performance goals
Imaging power where other wide-angle lenses fail: edge-to-edge sharpness captures stunning night scenes and is even suitable for astrophotography.
The shorter the focal length of a lens, the greater the viewing angle. With wide viewing angles, the use of broad apertures invites ugly aberrations and deteriorating image quality caused by light entering closer to the edge of the top lens. The lower the F stop, the greater the difficulty. To improve pictorial performance, technology must be applied to make a bright wide-angle lens.
Using 15 elements in 12 groups in fixed-length, internal rear-focus optics, with corner-to-corner sharpness and excellent rendering, this 12mm F1.4 demonstrates the superb image quality Leica users demand. The optics in this bright, extreme wide-angle lens are designed to ensure that when the fully-open F1.4 aperture lets in light, this light is controlled right to the edge of the capture. This is achieved by a powerful negative-meniscus element near the front of the lens configuration. In the new optical system of this 12mm F1.4 lens, the second element manages the light. This avoids pronounced barrel distortion, as well as the aberration and astigmatism that come when a negative lens is used at the very front. Placement of a positive lens in front of the negative meniscus lens suppresses the occurrence of both unwanted distortion and aberration. Moreover, image quality is further assured by the use of large-diameter aspherical lenses, along with regular extra-low dispersion glass and two ultra-extra-low dispersion glass elements which, working together, are designed to control image plane flatness, sagittal aberration, chromatic aberration and lateral chromatic aberration. This technology ensures that users enjoy fine resolution and excellent pictorial performance, even when capturing single-point light sources in night scenes and in other situations where wide-angle lenses do not usually excel.