Steve Spencer
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 p.9 #1 · Thypoch Simera 28mm f1.4 E-mount | |
philip_pj wrote:
A short look at the types of special glass and iris (aperture) blade counts we find in some high end fast lenses. Most abbreviations will be obvious, but Sim=Simera; Sum=Summilux; O/ML are the two new Zeiss Otus lenses; Z=Nikon S lenses; CV=Voigtlander; V=Viltrox; S=Sirui. '4s' refers to aspherical surfaces (not elements) where stated. 'B' is the iris blade count total across lenses in each category. Focal lengths of 28-50-75 were targeted.
It's a horribly complex subject, especially given the very poor uniformity of data. Much of it was very hard to find, some is simply unavailable, such as Leica's Q series' non-asph special elements - if any.
Main conclusions that are unambiguous:
Establishment lenses are very heavy users of aspherical surfacing, supported by relatively small numbers of ED/LD glass. APD glass effectively does the job of ED/LD glass for color correction. Apart from Viltrox, the Chinese makers use little ED/LD glass and below average levels of asph surfacing.
The two elephants in the graph that point to how the new Chinese lenses are delivering their excellence are:
. an extraordinary use of high refractive index (HRI) glass; and
. the 30% higher average blade counts in their apertures.
Though highly desirable (and expensive), HRI is difficult to manage because it produces troublesome levels of CA; this set off the increase in use of ED/LD and APD glass in the last 15 years or so. But it's very effective if done right, and probably necessary for ultra high image quality - Leica's 35/2 APO-Summicron-M uses it in three positive elements conjoined with APD elements in doublets, as an exxample. The Chinese are to be commended for their astute use of HRI, with minimal CA.
High blade count irises are very difficult to design, fabricate and assemble. If in doubt about this, do a search on: 'difficulty manufacturing photo lens irises'.
The Chinese makers all use a combination of HRI and several of them use very high blade counts, a format that has started to filter into establishment lenses in recent months. It's very likely these are the two major factors in the often excellent out-of-focus results we see in these lenses. ...Show more →
I hope you don't mind my offering a few corrections to your table:
The recent close focus version of the Leica 50 Summilux Asph has an 11 bladed aperture which was the other major update besides close focus to that lens.
All three Sony GM lenses (I assume you mean the 50 f/1.4 GM and the 85 f/1.4 GM II) have what Sony calls 2 extreme aspherical (the distinguishing feature of these is supposed to be the high level of polishing to avoid onion ring bokeh) elements not 4. They may well have 4 aspherical surfaces, but Sony doesn't really tell us that.
I think including the over 40 year old 75 Summilux design doesn't make much sense. When Mandler designed that lens it was a whole different world of lens design. The newer 75 f/1.25 Nocitlux gives a better example of what Leica has done recently. It has 2 Asph elements and an 11 blade aperture, but Leica doesn't tell us anything about ED, HRI, or APD glass at least as far as I can tell.
It also may not make sense to include the Nikon Z f/1.4 lens here as well. For the Z mount Nikon has decided to make all their f/1.4 lenses (unlike their f/1.2 and f/1.8 lenses) as budget lenses and not as their professional line of lenses. To me they are a bit oranges to the apples being considered here.
I think one of the important trends may actually be that the Japanese and European companies say a lot about aspherical elements in their marketing, but often say nothing about HRI and even ED and APD elements even if they are there. Leica in particular is notorious for that. So when these HRI, ED, and APD elements are not mentioned, I am not sure we can automatically infer they aren't included. What gets mentioned seems to be a marketing decision and not an optical design decision.
It is true, however, that the Chinese companies in your table (and I would add 7 Artisans and TT Artisans) often refer to HRI elements in their marketing. It is also true that Surui and Thypoch use higher blade counts (but I think this has more to do with their cine lens development than anything else).
All that said, thank you for the work of pulling this information together. I am just a lot less sure than you are that we can make the inferences you are making. I share your view that Thypoch, Surui, and Viltrox are making some really interesting lenses. I think they are producing some lenses that have great performance and exceptional value, but I am a lot less convinced they are doing something new or unique, or even doing the same type of things. I actually see these three companies as very different and what they mostly have in common is excellent products at a low price, but beyond that they seem very different to me with different areas of excellence and expertise.
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