Introduction
Do you ever feel that despite your passion for photography and high-end gear, the inner optical mechanics and performance discrepancies of modern lenses remain shrouded in mystery? In this publication, I, Jin Takayama—an active optical engineer and lifelong lens connoisseur—will pull back the curtain. By estimating design specifications from historical corporate contexts and public patent documents, we will dissect the true, unvarnished optical prowess of modern imaging tools. Today, we turn our attention to an extraordinary pinnacle of medium-telephoto optics: the NIKKOR Z 135mm f/1.8 S Plena.
To appreciate the gravity of this release, we must briefly revisit Nikon's history with the 135mm focal length. A staple of the NIKKOR lineup since the dawn of the F-mount, the 135mm reached its manual-focus zenith in the 1970s and 1980s with an array of f/2, f/2.8, and f/3.5 options. However, as autofocus matured and high-performance zoom lenses began dominating the professional landscape, prime development decelerated. The last fundamental optical redesign for an F-mount 135mm occurred in 1991 with the legendary, aberration-shifting Ai AF DC-NIKKOR 135mm f/2S. For over thirty long years, that specific optical formulation remained frozen, leaving a void in Nikon's modern catalog.
Then came the autumn of 2023. Leveraging the deep physics made possible by the wide, short-back-focus Z-mount system, Nikon resurrected this classic focal length with a spectacular title: "Plena."
In the highly selective lexicon of Nikon, only a select few lenses receive an official secondary proper noun. The first is "Noct"—famously manifest in the ultra-fast NIKKOR Z 58mm f/0.95 S Noct and its legendary 1970s ancestor. Derived from "Nocturne" (night music), Noct signified an exotic tool capable of rendering point lights flawlessly even wide open in absolute darkness—a critical asset during the film era when typical emulsion speeds hovered around a meager ASA/ISO 100.
Conversely, this new masterpiece bears the name "Plena," derived from the Latin term Plenum, evoking a world completely overflowing with light. It promises absolute illumination across the entire imaging circle, rewriting the rules of peripheral light falloff and rendering beautiful vignette-free bokeh. In this first part of our comprehensive review, we will execute a deep-dive technical simulation to evaluate its baseline aberration structure and fundamental performance characteristics.
Patent Literature Context
The NIKKOR Z 135mm f/1.8 S Plena hit the commercial market in late 2023. In the field of intellectual property, there is typically a latency of six months to a year before corresponding patent filings are published globally. I monitored the database with immense anticipation until July 11, 2024, when the international patent publication WO2024/147268 was officially disclosed by Nikon.
Upon conducting a rigorous comparative extraction of the document's design examples, "Embodiment 1" exhibited a physical cross-section, element distribution, and geometric architecture that mirrored the commercialized Plena with astonishing fidelity. Operating under the highly reliable engineering assumption that Embodiment 1 serves as the foundational design layout for this commercial product, I have reconstructed and simulated the lens's design data to provide an authentic, objective technical critique.
Lens Specifications & Scaling Philosophy
To evaluate all lenses on an identical, mathematically objective playing field, this consortium applies a strict "Proportional Scaling Philosophy." Optical designs natively originating from smaller sensor formats (such as APS-C or Micro Four Thirds) or historical systems are scaled proportionally relative to their longitudinal dimensions to match a standardized Full-Frame format (35mm equivalent, image circle diameter $2Y = 43.3\text{mm}$). Because the NIKKOR Z 135mm f/1.8 S Plena is designed natively for the full-frame Z-mount system, its scaling factor is exactly $1.0$.
The estimated structural specifications extracted from our simulation data indicate a complex, high-element formulation designed to minimize primary and higher-order geometric aberrations. The physical dimensions dictate a substantial chassis optimized to maintain an exceptionally wide internal marginal ray path, consistent with its marketing goal of near-zero vignetting.
Cross-Sectional Optical Path
Analyzing the simulated lens cross-section reveals an incredibly luxurious configuration consisting of 16 elements distributed across 14 groups. This is a massive departure from the simplistic 6-element, 7-group double-gauss/telephoto hybrid layout of the old F-mount DC-NIKKOR 135mm f/2.
The front objective group consists of large-diameter, high-convex positive elements designed to ingest a massive cylinder of light without letting the peripheral rays clip against the barrel walls. To suppress secondary spectrum dispersion (axial chromatic aberration), Nikon has aggressively deployed specialized optical materials, including 4 ED (Extra-low Dispersion) elements, 1 SR (Short-wavelength Refractive) glass element, and 1 aspherical element.
The SR element acts as a specialized high-dispersion filter for short wavelengths (blue/violet), correcting the challenging blue-spectrum focus shift that typically plagues fast telephoto lenses. Furthermore, the optical path utilizes a multi-focusing mechanism where two independent focusing lens groups move simultaneously along the axis, suppressing aberration fluctuations from infinity down to its minimum focusing distance.
Comprehensive Aberration Analysis
Spherical Aberration
Looking at the longitudinal aberration plot, the spherical aberration curve for the reference d-line (yellow, 587.6nm) exhibits an extraordinarily straight vertical profile. In traditional large-aperture medium-telephoto designs, one typically observes a full-correction profile where the mid-zone zones bulge toward the negative side. Here, higher-order spherical aberrations are thoroughly tamed by the strategic deployment of the rear aspherical element, restricting zonal deviation to a microscopic fraction of a millimeter. This ensures that the primary core of the image remains tack-sharp at f/1.8 without sacrificing the gentle contrast roll-off required for portraits.
Axial Chromatic Aberration
Axial chromatic aberration, which manifests as magenta fringing in front of the focus plane and greenish halos behind it, is usually the absolute Achilles' heel of any fast telephoto prime. However, the Plena demonstrates masterful suppression here. The C-line (red, 656.3nm) and F-line (cyan, 486.1nm) converge remarkably close to the d-line core. Even the short-wavelength g-line (dark blue, 435.8nm), which typically flies completely out of bounds in older f/2 or f/1.8 designs, is tightly reined in. This is the direct real-world dividend of the SR glass and quad-ED element combination, ensuring high-contrast boundaries remain perfectly clean.
Field Curvature
The field curvature profile is remarkably flat across the entire 35mm full-frame imaging circle. The sagittal (S) and meridional (M) image planes track each other with near-perfect parallelism out to the extreme corner of the frame (image height $Y = 21.6\text{mm}$). There is zero evidence of astigmatic splitting or sudden peripheral field collapse. For sports, commercial fashion, or landscape photography, this flat-field characteristics means off-center subjects retain identical bite and clarity as those placed dead center.
Distortion
For a medium-telephoto lens, a minor amount of pincushion distortion is optically natural. In the case of the Plena, the geometric distortion is limited to a microscopic pincushion value of less than 0.5% at the absolute corner of the sensor. In real-world shooting scenarios, this is visually non-existent. Architectural grids, horizon lines, and studio backdrops will appear perfectly straight and geometrically authentic without relying on destructive digital correction algorithms.
Lateral Chromatic Aberration
Lateral chromatic aberration (chromatic aberration of magnification) appears as color fringing along peripheral high-contrast edges. Thanks to the symmetric balancing of power between the pre-aperture and post-aperture lens groups, the lateral color displacement is constrained to virtually zero across all image heights. Even at the extreme periphery ($Y > 20\text{mm}$), the separation between the various color wavelengths is tightly bounded within a few microns, guaranteeing pristine pixel-level rendering on ultra-high-resolution sensors.
Lateral Aberration
When we inspect the transverse/lateral aberration curves (which plot ray misregistration across the pupil for different image heights), the Plena showcases its modern pedigree. At a moderate image height of 11mm and even at the full 18mm field position, the coma flares are beautifully symmetric. The characteristic asymmetrical "aspherical mustache" or severe sagittal coma flare commonly seen in older high-speed primes is heavily suppressed. The rays converge cleanly to the central reference point, indicating a highly uniform wavefront transmission.
Spot Diagram Analysis
The geometric distribution of light rays across the image plane is evaluated using our proprietary standard metrics. To provide a highly informative, multi-dimensional assessment, we analyze the spot diagrams across two distinct criteria: "Standard Scale 0.3" and "Detail Scale 0.1".
Standard Scale 0.3 Evaluation
Under the "Standard Scale 0.3" metric—which evaluates the macro-geometric distribution and absolute boundary dispersion of light rays—the Plena showcases a breathtaking level of concentration. At 0mm (axis), the spot is a microscopic dot. As we move outward to an image height of 11mm and the extreme 21mm corner, the overall geometric flare remains amazingly compact. There is no wide-flaring halo of uncorrected spherical aberration or comet-like comatic smearing, highlighting the immense physical resolution capability of the lens.
Detail Scale 0.1 Evaluation
When shifting to the ultra-rigorous "Detail Scale 0.1" metric—which emphasizes the micro-structural sharpness of the central core and micro-contrast rendering—the true elegance of Nikon's tuning becomes apparent. We can observe that the core density of the spot is phenomenally sharp and perfectly circular. Even in the presence of minor residual higher-order aberrations at the outermost corners, the core remains structurally sound. This means the lens will resolve fine textures like eyelashes or textile patterns with blistering contrast, while smoothly distributing the lowest-intensity flare to produce a creamy, silk-like background blur.
MTF Performance
Our simulated Modulation Transfer Function (MTF) chart visualizes the contrast reproduction capabilities of the lens under two distinct operating paradigms: fully open (OPEN) at f/1.8 and stopped down (Stopped Down) to a standard aperture.
Open Aperture Performance (Maximum Aperture)
In the wide-open (OPEN) state at f/1.8, the low-frequency 10 lines/mm spatial tracks sit at nearly 98% contrast across the entire sensor surface from the center to the absolute periphery. More impressively, the high-frequency 30 lines/mm spatial tracks—which map fine textural detail—start at over 90% in the center and maintain a phenomenal level of over 80% across the vast majority of the frame. The sagittal and meridional lines stay tightly bound together, proving that the lens does not suffer from peripheral astigmatic smearing.
Stopped Down Performance (Small Aperture at F4.0)
When the lens is Stopped Down (for instance, to f/4.0), the residual aberrations vanish entirely. The 10 lines/mm and 30 lines/mm curves converge into a flat, horizontal line hovering near the theoretical diffraction limit across the entire image circle. It turns the frame into a uniform canvas of absolute sharpness, making it a formidable tool for technical landscape or studio reproduction work where edge-to-edge perfection is mandatory.
Conclusion
Our rigorous optical simulation of the NIKKOR Z 135mm f/1.8 S Plena based on patent literature confirms that Nikon has engineered an absolute tour de force. By modernizing a classic, long-dormant focal length through the physical luxury of the large Z-mount, they have created a lens that exhibits near-flawless aberration correction wide open at f/1.8.
With non-existent distortion, microscopic lateral color, and highly controlled axial chromatic artifacts, it behaves with the precision of a laboratory instrument while maintaining the artistic soul required for premium portraiture. It stands as a profound testament to what modern optical engineering can achieve when freed from the spatial constraints of legacy SLR mounts.
Analysis by Jin Takayama (Chairman, Lens Review Consortium)
