01-29-2015, 10:29 AM
Quote:We're back to acronyms again, what BK7 when it's at home?
This will be explained in some new PZ articles.
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01-29-2015, 10:29 AM
Quote:We're back to acronyms again, what BK7 when it's at home? This will be explained in some new PZ articles.
01-29-2015, 07:09 PM
It is clear, this lens is over priced, and it's cost has nothign to do with its pricing. I beleive the price is set to reflect the uniqe qualities of the lens, and to give some room to marketing to run promotions and still make profit. Hopefully it will worth the money paid by the users.
Kaus, are planning to torchure it in the lab?
01-29-2015, 07:36 PM
Quote:How long do you figure? Again, where are you sourcing your information? A 4" diameter surface defined by zerneke polynomials takes about 17 hours to polish via MRF to 1/50th wave precision. I just polished this part about a month ago, I am speaking from direct experience. If the max surface departure was smaller it would take much less time. Drop precision to 1/20th wave and the estimated time from the machine was 4 hours to do the polishing. At 1/10th wave precision there is a question of why use MRF, and the traditional, non-deterministic polishing and grinding methods may produce a spherical 4" diameter lens in just an hour for the grinding and 10 minutes or so for the polishing. At 1/20th wave the traditional methods can produce the curve in perhaps 3 hours, tops. Smaller diameter parts happen faster, and bulk grinding and polishing machines which use very large planetary heads can produce many pieces at once. Your "considerably" claim is baseless... yes these are $100,000+ machines doing the work, but operational costs are low and the manufacturing engineers have maximized speed without breaking some percentage of the blanks that get turned into lenses. Quote:First half true, second half only true because it mandates the second part. The sag is greater for smaller radii of curvature thus you require a thicker blank to produce the lens except in the case where a thinner blank is heated and roughly pressed (aka bent) before being ground. Quote:Standard for-the-eyes precision is 1/4th wave. Cheap optics are 1/10th wave and are "low precision." 1/20th wave is the standard for photographic instruments. 1/50th is high precision and baseline lab spec. High tier lab spec is 1/200th wave or better but that level of precision is excessive except when analyzing very small characteristics or when dealing with extremely high energy experiments. "Higher precision" is only mandated when using an asphere or other atypical lens shape because these shapes are more difficult to produce. Quote:Why is it odd? Just how large an industry do you think optics is? The machines that print the processors in all of your computers are at this stage costing billions of dollars each for the optical systems. Intel most likely prints more processors per year than the entire optics industry sells objective elements. ---- Quote:BK7 is the most common and cheapest optical glass. All other glasses are priced relative to BK7 - e.g SF4 (a dense flint) being 6x BK7's price from Schott. Quote:Fluorite (CAF2) is simultaneously a wonderful and terrible material. Everyone would love to design with it because it can fix most of the problems with correcting blue light (bye bye purple fringes, bye bye blue chromatic aberrations, etc etc) through the change of a single material. It has what is known as anomalous partial dispersion which means it spreads out blue less than would be expected. It is a wonderful material. Unfortunately it is phenominally expensive (100-1000x the price of BK7 depending what "strain" of CAF2 you want) and fragile enough that simply breathing in its general direction can cause it to crack. This is an exaggeration of course, but many manufactures (i.e the people doing the manufacturing, not canon nikon etc) will refuse to work with CAF2 and other materials of its family simply due to the difficulty in working it. I have a friend with a 6x6x6" block of CAF2 on their desk. It has a single hairline fracture through it so it is worth $0. Its value were it usable would be about $10,000. Last year Schott discontinued their production of CAF2 entirely and Ohara is looking to do the same in the near future because it is simply too much bother. This will not affect canon or nikon who produce their own but does mean that other manufactures of optics, both photographic and for other uses, will begin to phase out use of it presently. Minor note as well - CostalOptics is the brand or line of the 60mm. JENOPTIK is the manufacture . It was designed by Brian Caldwell, a designer I share many mutual contacts with but do not at this time know personally. Its wonderful correction is due to the use of many glasses of CAF2's family, allowing the correction into UV and near IR as well as visible. This is not possible with traditional or more common glasses.
01-30-2015, 02:53 PM
01-30-2015, 04:29 PM
Quote:It is clear, this lens is over priced, and it's cost has nothign to do with its pricing. I beleive the price is set to reflect the uniqe qualities of the lens, and to give some room to marketing to run promotions and still make profit. Hopefully it will worth the money paid by the users. Sure.
01-31-2015, 09:47 AM
Looking at the list of lenses tested... Klaus, you ALMOST made it before it's time to start over with a higher MP sensor. Testing is really a Sisyphus's labor.
01-31-2015, 10:53 AM
Bleh. At least those 50mp will be good enough for many years to come. Doubling that will be difficult.
Honestly - personally I would never buy such a thing. Conceptually I am more intrigued by something like the A7s.
02-02-2015, 01:42 PM
http://translate.google.com/translate?hl=&sl=ja&tl=en&u=http://digicame-info.com/2015/02/ef11-24mm-f4l-2.html
More details from this upcoming lens. 1180 grams, quite the heavyweight. |