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 p.17 #17 · Nikon Z 35mm 1.2 S - Official Image Thread | |
I want to touch on the 'unacceptable' LoCA, particularly in light of the Viltrox's performance at a lower price point. If I were to channel the drama of certain comments, we should be up in arms about Nikon taking its users for a ride. Then I’ll stop rambling about this lens now, I’ve already said more than enough, since I want to move on and share my experience with the ZR (long story short: mixed feelings).
Let’s start with the premise that no one would ever build a 35mm full frame lens longer than 15cm or wider than 10cm; even those dimensions are enough to make fans of this focal length cringe. It would simply fall outside the acceptable form factor for how this type of glass is typically used. Consequently, there is a physical limit to the number and diameter of elements that can fit into such a housing (roughly 15). Since you can’t have the cake and eat it too, you have to decide on a specific direction for the optical design and determine which compromises are worth making.
With around 15 elements at your disposal, you must decide on the number of independent elements versus doublets or triplets, as well as how many special dispersion glasses to incorporate. Each choice involves trade-offs, which I’ll summarize here, without claiming to be exhaustive or perfectly precise:
1) Numerous independent elements with few cemented groups: This is a much costlier approach due to the complex construction of the barrel and spacers, tighter tolerances, higher production waste, and the need for near perfect centering. However, it offers significant flexibility in distributing dioptric power across many surfaces. It excels at correcting higher order monochromatic aberrations and allows for independent adjustment of spherical aberration and field curvature, though it possesses less corrective power for chromatic issues (including LoCA). Simply put: you can effectively flatten the field curvature and gain much finer control over rendering and image quality. Furthermore, since the lens groups are lighter, using dual motors can almost entirely eliminate focus breathing. This is the typical design for cinema lenses, which derived from the Zeiss Distagon formula, and is the route Nikon took for the Z 35mm f/1.2 S, featuring 17 elements in 15 groups (with only two doublets).
2) Multiple doublets and fewer independent elements: This is Viltrox's choice, using 15 elements in 10 groups. By utilizing four doublets, they gain four independent degrees of chromatic freedom. This allows for more effective correction of primary chromatic aberration and reduces secondary residuals by distributing correction across multiple glass pairs with complementary dispersions. This layout provides vastly superior control over LoCA, but at the expense of field curvature and rendering. 'Rendering' here isn't just about better bokeh; it’s about achieving superior spatial and color balance across the entire frame. This lens prioritizes high center frame acutance, making it ideal for environmental portraits with a centered subject, especially if it features a slight under correction of spherical aberration that yields smoother background bokeh (at the expense of busier foreground bokeh). Its advantage diminishes, though it still performs admirably, when the subject is off-center. However, it isn't suited for professional video work; detail drops off as the subject moves across the focal plane, and the more pronounced field curvature causes the focus to hunt or drift more frequently with moving subjects, even when they remain on the same plane. Presence of focus breathing.
Let’s compare some real world data, taken from Photographylife (with the caveat that since no methodology is provided, we have to take these figures on faith). At wide open aperture, the Nikkor shows 0.77 pixels of CA compared to the Viltrox’s 0.50. The Imatest scores for the Nikon are 2,549 (center) / 2,542 (mid) / 1,623 (corners), whereas the Viltrox hits 3,552 (center) / 2,310 (mid) / 1,687 (corners). I'll set aside vignetting, which is far more pronounced on the Viltrox, and distortion, where the Viltrox shows complex, irreversible pincushioning versus the Nikkor's linear barrel distortion.
These figures align with my previous points and invite some interesting analysis. The LoCA values are excellent for both; you’d really have to hunt for specific edge cases and pixel peep to notice it. However, staying below 0.50 pixels provides a distinct boost in perceived overall definition. This is further bolstered by the Viltrox’s staggering central score of 3,552, which makes the Nikon’s 2,549 look modest by comparison. While the Nikon is still 'highly sharp,' one can’t help but admire the Viltrox.
The downside appears as soon as you move away from the center: the Nikkor maintains its central sharpness across the mid frame, whereas the Viltrox's performance drops to 2,310, losing its lead. Corner data is similar for both, which is simply a physical limitation of full frame wide angles at these apertures. The Viltrox feels unbalanced; this drop off is a strong indicator of poorly managed field curvature. In contrast, the Nikkor is far more consistent and balanced, exhibiting the flat field one would expect from its complex optical formula.
Have you noticed that the product page on Viltrox’s website features exclusively center composed portraits? In contrast, Nikon’s page showcases a wide variety of work: off center subjects, group shots, and even a short film that explores the various facets of the Nikkor’s video capabilities. Marketing material is always the biggest "tell".
A brief note on special dispersion glass: while these are powerful tools for controlling chromatic aberration, they tend to produce a spectral transmission slightly biased toward shorter wavelengths. This often results in an unbalanced color response with a subtle cool cast. Viltrox utilizes a staggering eight of these elements, whereas Nikon uses three, one of which, however, is an 'exotic' aspherical extra low dispersion element that is significantly expensive to manufacture.
In its 35mm f/1.2 Art II, Sigma utilizes only a single SLD element. Are Sigma and Nikon truly the photography leviathans being toppled by Viltrox’s muscular designs? Or is it simply that special glass is no longer as costly as it was decades ago, and a truly well engineered lens isn't one that is stuffed with specialized elements, but one that uses them strategically to reap the benefits without compromising the overall rendering?
To summarize the points made so far: Viltrox has attacked the lens market in the cleverest way possible for a third party manufacturer. Breaking into a closed system like Nikon or Canon, who survive on both body and lens sales, is far more complex than entering Sony’s relatively open ecosystem, where Sony scales by selling components.
And what was their strategy? An unbalanced optical design entirely dedicated to achieving a peak in central acutance, while aggressively nuking LoCA with four doublets and eight special dispersion elements: a literal 'chromatic task force.' It is a simple approach, and far cheaper than producing a balanced, well-engineered design, but it achieved exactly the desired effect: the scores at the center of the MTF charts and Imatest results became stellar. This, in turn, thrilled bloggers and influencers who, like peacocks in spring, began strutting about without the slightest idea of how to interpret these figures for what they really are: purely virtual. Indeed, these peacocks were quick to fan their feathers. Two photos of a flower, one of a cat, one of a ruler, and a quick clip to see if the autofocus hits the books on a shelf, and that was enough for them.
Naturally, testing a professional-grade product requires simulating professional workflows, and that’s exactly when all the dust swept under the rug starts to show. Try shooting an entire professional video with the Viltrox versus the Nikkor and we’ll talk, or try selling a set of photos featuring irreversible pincushion distortion on every single frame.
That said, this isn't a 'slander' of the Viltrox; in reality, it’s a very nice lens. It is primarily aimed at amateurs and is worth exactly what it costs (and no more). It allows anyone to enjoy a popular focal length at an ultra-fast aperture for a relatively modest price. It perfectly covers the needs of most hobbyists, producing files that will offer great satisfaction and enjoyment. It’s also an excellent option for portrait photographers who typically rely on telephoto lenses but want to add a few environmental portraits to diversify a portfolio without investing in an 'overkill' solution.
The Sigma and the Nikkor are in a different league altogether. The former takes a somewhat conservative, middle-ground approach; it is an excellent, well-balanced professional lens that delivers consistent results and a beautiful, watercolor-like background rendering. The Nikon performs similarly for stills, boasting even better parameters and a more neutral, 'veiled' rendering thanks to its superior correction of field curvature and spherical aberration, yielding beautiful bokeh in both the foreground and background. However, it is in its professional video pedigree where it truly sets itself apart, leaving the others far behind. Both feature a more refined optical design, better engineered, costlier, and more complex, with the Nikon pushing that standard even further. The problem, in my view, arises when someone tries to pass off a lens like the Viltrox as a professional grade tool that has finally 'lifted the veil of Maya' on a global conspiracy of major brands fleecing their unsuspecting customers. This is especially frustrating when it comes from a blogger who claims their commentary is objective and scientifically grounded.
To crown this long and tedious rant, I’ll leave you with a 'reviewer style' LoCA test of a $30,000 cinema lens: specifically, the most renowned of them all, the ARRI Signature 35mm T1.8. Scandalous! Quick, somebody send the Viltrox to Hollywood. 
https://ibb.co/0yxy1vrP
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