![]() Prior to polishing, the shape of the mold is measured very precisely, producing a surface profile plot of the sort I mentioned earlier. Panasonic has improved the end steps of their aspheric mold processing technology to greatly reduce surface roughness ![]() Panasonic was careful to say that this polishing step was only part of the complete process, and that other parts of the process are responsible for much of the reduction they've achieved in onion-ring bokeh, but I found the manual polishing step fascinating, nonetheless. The small image inset right shows a mold being polished by a worker, which gives you a general idea what the setup looks like. One stage of the process involves manual polishing of the molds. This is a process they developed over the course of about two years, but one I unfortunately have very few images to illustrate, given its proprietary nature. That's smaller than the smallest viruses, and only about 1/25 the wavelength of green light. The level of precision they've achieved in pursuit of this goal is astonishing: At the end of their production process, the final molds have a total peak-to-valley roughness of just 20 nanometers. While they were deliberately a little mysterious about exactly how it was accomplished (and asked me to do the same -), Panasonic has found a solution to this problem. (Again, this is based on Nikon's information in the link above I welcome any correcting information readers might have, via the comments section below.) (According to Nikon, at least.) Aspheric lenses became more common in the 1980s, but grinding was the rule of the day until 1993, when Nikon released their 18mm f/2.8D prime lens. Aspheric lens elements were first brought to practical use by Nikon, in 1968. Because they were formed by a grinding/polishing operation, it was also difficult to make aspheric elements from high refractive index glass, which is generally much harder than conventional glass, and so would wear down the grinding tools quickly. ![]() As you might expect, this made aspheric lens elements extremely expensive. Previously, aspheric lenses could only be created by a very exacting, time-intensive grinding process, that was ill-suited to mass production. Aspheric lens elements help reduce spherical aberration and other optical problems in complex lenses, and let lens designers create better lenses with fewer elements. Molded aspheric lenses have been one of photography's great technological developments of the last few decades, bringing dramatically improved lens performance at affordable prices. To understand onion-ring bokeh, then, we need to look at how aspheric lenses are made. There, I met with Hirotsugu Yabuta, Director, Optical Devices Business Unit (the manager of the Yamagata factory), Kazutake Boku, Manager, DSC Business Division (Panasonic's head lens designer), and Koji Fujita, Imaging Team, Communication Group, Overseas Consumer Marketing Center (a member of their global marketing team, who served as translator, facilitator, and general ombudsman for my visit).Īs it turns out, onion-ring bokeh is the result of modern Precision Molded Optics (PMO) technology, a technique used to make aspheric lens elements. ![]() Until now, onion-ring bokeh has been a more or less unavoidable consequence of using aspherics in certain parts of lens designs, but I learned on a visit to their main Yamagata lens factory in mid-February of 2014 that Panasonic has apparently beaten this problem. Lenses with aspheric elements inside have less spherical aberration and are considerably smaller than similar ones designed without aspherics.Īs they say, though, there's no free lunch, and modern aspherics have brought along issues of their own, including something called "onion-ring bokeh". until now.Īspheric lens technology is part of the reason many modern photographic lenses are better in so many respects to models from 50 years ago.
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