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 p.93 #3 · Light Lens Lab (LLL) replica lenses discussion & image thread | |
Steve, thanks for the response. The issue I mentioned is not so much 'quality' as the missing word also - 'quality control' is one of the issues Neil highlighted. It's interesting that Cosina is now backing away from aspherics in even their APO lenses. They are now an exemplary spherical lens company, leading the way in the stills world, using their very fine own manufacture spherical glass!  Maybe we will soon see lens front plates proudly displaying 'SPHER' or similar. lol.
The Cooke s8/i lenses (full frame, T1.4) 'cost around $34,650 to $36,100 USD each', so I guess Neil's concerns lie elsewhere than costs - primarily in 'the look', design, assembly.
We've see plenty of posts about CV lenses with misalignment over the years, haven't we? Not that we can say this is greater or lower than other lens brands And in fact it may be that users of high end MF lenses are more on the lookout than regular AF camera users.
On designs with aspherics, permit me to make a longer post in the hope it may interest some readers.
Iain Neil: 'During the past five or more years, I kept hearing that images produced by digital cameras mostly looked the same, the words “clinical, sterile look” were heard often. This seemed to be bothering a lot of cinematographers.'
'I said, “Well, maybe future lenses should be designed so that the images are more film-like, as opposed to digital.” We had aspherical surfaces in cine optics around the 1990s. And those types of aspheres, unfortunately, took a direction where the imaging appeared clinical or sterile.'
'The point is that we don’t need to be quite so obsessed with resolution. The key is contrast. In my view, you want to maximize the contrast. So, when the S8/i project began, I said, “We don’t really need the aspherical surfaces—they are not magical.'
'With spherical optics, you can design lenses that perform very well—maybe not to super high resolution levels, but certainly sufficient, and quite ample, for digital cameras not just today, but even in 5 or 10 years from now. Spherical optics can do just as good a job as lenses with aspherical optics.'
'Furthermore, in designing spherical lenses, you can produce a near telecentric output of the light rays that is nice for the sensor. It makes the sensor efficient. There are additional reasons for not having aspheres, whether pressed, molded, polished, ground, or other methods. One of them is the alignment, how precise you have to align aspheres, and the fact that over time, you may lose the alignment.'
'The other issue with aspheres, especially when ground and polished, is the possibility of seeing “onion
rings,” or “tree rings” in the bokeh. It’s not always the case, but it can show up. With spherical lenses, you have smooth-looking bokeh, without onion or tree rings.'
'But if for no other reason, not having aspheres makes a huge difference—it’s a large factor. In designing earlier lenses at Cooke, they always said, “See these damned aspheres. They’re a bloody nuisance. They’re difficult to source. Then we get them, and they’re not the right quality. They charge lots of money. We can’t get the volume. We can’t build enough lenses.” So, the word was out, get rid of aspheres.' (The Cookes are not just portrait length, they start with an 18/T1.4!) cheers.
quotation from: https://www.fdtimes.com/issues/ (April 2022 issue, pp. 18-21)
https://cookeoptics.com/lens/s8-i-ff/
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