Discussion in 'Medium Format' started by RaymondC, May 30, 2020.
Utraviolet light. Plain ordinary white light won't do.
In 1899, Charles H. Duell, Commissioner of the US Patent Office, declared there was nothing new to invent. He was wrong, and so is @antioniobravo.
Mechanics and electronics have little to do with lens quality.
Before 1980, lenses were designed with ray-tracing calculations performed by teams of mathematicians with desk calculators. Few of the best lenses had more than 8 elements and many had 5 or less. There were fewer choices of glass at the time, and coatings were much less efficient. More elements resulted in better correction and resolution, but less contrast.
Now, multi-layer coatings are over 99% efficient, which means more elements can be employed with acceptable loss of contrast. Mirrorless cameras require less back focus distance, so less design effort is expended to compensate for mirror clearance. With modern ray-tracing software, the designer can quickly verify the performance of various lens designs, and modify the design to meet certain performance specifications. There's still a bit of art and science involved. Other factors include size, weight and cost, and the ability to accommodate normal manufacturing tolerances. The last is often secondary in the design of high-end video lenses, which are hand assembled and tuned. Bargains in this category start at about $5000 for prime lenses and $10K or more for zooms.
Natural thorium has an extremely long half life, and decays primarily by alpha emission. Alpha particles are most dangerous if ingested, because they tend to settle in the growing ends of bone (calcium analogues) and other organs. Otherwise, alpha particles cannot penetrate the skin, and are stopped even by a sheet of paper. Thorium glass is no longer used because (a) it yellows the glass with age, and (b) it must be disposed as hazardous waste to keep it from entering ground water.
Every element with an atomic number greater than bismuth (83) is subject to radioactive decay. This includes lanthanum, which is still used in glass, along with other transition elements.
If there are any conclusions beyond economics, don't eat lenses, and don't carry them in your pockets if you are younger than 50.
Exposure to sunlight for a week or two will remove the yellowing. Sunlight is white by convention, but has ample UV to do the job.
Mechanics, I would argue, do have a fair bit to do with quality at least up to a point because correct and consistent positioning of the lens elements is essentially step 0 in designing a high performance lens.
Also, more advanced systems of floating elements for zooming and focusing both can, in theory, produce better or at least more consistent performance. That's also subject to using the correct materials, as if, for example, a cam wears to the point that it no longer consistently places the elements, or consistently moves them to the wrong position, the consequences are obvious. Even a poorly manufactured one, if new, can perform badly or inconsistently out of the box.
I don't think optical innovation is done, but I do think that now we are likely at the point of diminishing returns. I don't see great advances coming of the sort that have changed things in the past, like lens coatings, low dispersion glass, or computerized lens designs, but have no doubt that things will continue to improve, and hopefully in lighter packages(some standard zooms and even primes have become pigs even though they're much better than older equivalents).
Modern prime lenses for mirrorless cameras have 15 or more elements, for optimum performance with high-resolution sensors. Zeiss, in particular, design lenses for consistent rendering between focal lengths in a particular model line (e.g., Loxia, Batis, Otus), and uniform sharpness across the FOV, rather than ultimate sharpness in the center. Zeiss mirrorless lenses tend to have high color contrast, which is striking when compared to legacy Leica lenses and most Nikon lenses for DSLRs.
WRONG!!!!! Educate yourself. Check photo dealers and auction sites and you will find the prices to be $1,000 or more depending upon condition. Given that the original M-3 cost under $300 I would venture to guess that intention notwithstanding LEICA cameras have proven to be investments.
WRT Thorium glass being only an alpha emitter:
True it starts out that way, but the daughter decay products of Thorium are gamma emitters, and if you pick up one of those, invariably > 50 year old, lenses, you'll find that its radioactivity will now pass right through a lead brick to give several hundred counts/second on a Geiger detector!
Personally, I wouldn't care to spend too much time in the same room with one. Let alone carry it in my pocket.
Thorium 230 has a half life of 77000 years & Thorium 232 has an even longer half life (14,000,000,000 years), there's not much difference in the composition after only 50 years. Immediate daughter decay products also have long half lives (Radium 226 is 1620yrs giving of alpha & gamma, Radium 228 is 5.8 years emitting beta)
Lenses with high activity through lead bricks have almost certainly been contaminated by other radioactive material since being made, that sort of signal would not occur from pure Thorium after only 50 years (which is less than 1/1500 of a half life, even for the less stable form). In this time less than 0.05% of the initial thorium has decayed.
If such a lens exists chances are someone has decreed 'the lens is radioactive so it must be stored with other radioactive material'. In the sort of location this could happen the radioactive material it's stored with could be MUCH more radioactive than the lens itself.
Surface contamination is the main reason I'm involved in radioactivity (site deputy radiological protection supervisor), Ash & sludge on site concentrating up trace NORM (naturally occurring radioactive material) to the point it falls within legislation. Radioactive lenses are more active than our NORM, but they don't spread nearly as easily.
I'd be happy to spend the rest on my life with a typical radioactive Takumar in my bedroom (except when I take it out to use).
That wasn't the opinion of our radiation protection officer, who tested two separate lenses at my request, and whose calibrated radiation meter was used.
He consulted a chart of radioactive isotopes, upon which were clearly shown Thorium decay products with gamma-emitting properties. And I doubt that random post-production contamination would have equally affected both a 7" f/2.9 Aero Ektar, and a 12" f/9 Cooke Apotal process lens in exactly the same way. Neither of which had been specially stored, and certainly not with other radioactive products.
Moderately strong gamma emitters aren't the sort of stuff that just gets picked up casually.
I still shoot 8x10 and 4x5 and 120 with Rolleiflex and Pentax 67. I still make prints, mostly platinum but some silver. Everything and every opinion expressed in this thread is a moot point. Barking up the wrong tree, pissing in the wind. All the technical stuff you are talking about is just nerdy head up your ass kind of thing. Everything done that is of value is primarily done with your mind. If you think that using a lens that gives you this amount of lines per mm versus what that lens gives you then you are a hopelessly head up your ass nerd. Study art, not lens designs. Find a camera that feels good in your hands. Make prints... not just digital files or contact sheets. Finish your work.
When you're using tools that allow you to do what you want to do, to the standard you set, it is easy, but rather naive, to believe that the quality of those tools doesn't matter.
Strangely, you're the first person in this thread to even mention lines per mm.
Mmm-hmm. Some home truths in that sentence. Studying art will be easy for those who can create through their mind's eye and conceptualise ideas. 'Twill be completely lost on those who are head-over-heels enamoured and addicted and besotted by technology and automation that only serves to obstruct the path to creativity.
The cameras I use don't actually, really "feel good in [my] hands"
But they are only tools to get the job done, not the Mona Lisa. Another day, more work...
I think I last paid any attention to that floss around 1984...
I see the invention of photography as being a paradigm shift in the field of art. By commencing to democratise the process of representational image-making.
With time, advances in technology and mass-production have increased the reach of that democratisation process; to the point where the majority of the world's population can now readily capture images from life.
Witness the explosion of images and creativity displayed on the internet. Many mundane, agreed, but also many showing a degree of creativity, and indeed expression of beauty and individuality, that would otherwise be denied to their creators.
Only technology has made that possible.
So who cares if autofocus, auto-exposure, digital processing or any other technical aid was involved? The important thing is that a worthwhile picture has been brought into existence, and/or perhaps an important slice of history has been captured. A picture that you, I, or anyone else is free to enjoy (or endure). A picture that someone was free to create without undergoing a lengthy apprenticeship in painting, drawing, chemistry, or other tedious obstruction to their creativity.
Solely because of technology.
I speed read most of this because it started to get bitchy and childish, but I do have a few questions. What is art? Whose definition of art do we study? When we have studied it, what might we learn?
IMHO vision and technique.
Good point well made.
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