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  1. #121
    Sparky's Avatar
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    Quote Originally Posted by fdisilvestro View Post
    I think that the Biogon formula was changed for environmental reasons, not because of cheaper glass. As fas as I know, the new formula is lead-free.
    definitely. that too.

  2. #122

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    Quote Originally Posted by Sparky View Post
    Honest to god, QG. Not. I was trying to suggest it would be well worth their while, cheaper and smarter to reformulate to something that uses LESS glass, where possible.. if it becomes less expensive to manufacture - and the lens is just as great... why not??? I wasn't ever trying to suggest that they compromise on their quality at ALL. But a large manufacturing company like Zeiss, I'm sure, has a LOT of pressure on it to save money where it's rational and where it doesn't compromise the quality of their product...

    that's all I was thinking I guess...
    Don't forget that Zeiss sell products at a price reflecting that those are of uncompromisingly high quality. And that people happily (well...) pay that price. So they are doing pretty well.
    So i don't know about that pressure... what pressure?

  3. #123
    Sirius Glass's Avatar
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    Quote Originally Posted by Q.G. View Post
    They didn't.

    Anyway, you can't change glass for cheaper glass, having the same properties.
    If it doesn't have the same properties, the design is of no use and you need to start again. If it does, it is the same as the one that would be more expensive, so why would it be cheaper?

    Zeiss, by the way, make their own glass, are their own source. Schott is part of the Zeiss conglomerate, ever since Carl Zeiss, Ernst Abbe and Otto Schott got together in the 1870s.

    And Schott is very capable of producing glass that is in spec.
    You know, it's not just a freak accident that they do. Nor that they do that routinely.

    So i can guarantee you that it never happened.
    Quote Originally Posted by Q.G. View Post
    Well, Sparky... you can dismiss being professional about what you do as being religious. You can also try to shrug criticism off as being religious.

    The plain and simple truth (of the non-religious kind) however is that what you said was BS.

    It really is.
    Why, pray tell, do you want to suggest that someone said that everything Zeiss did and does is perfect, while noone did? Who gave Zeiss too much credit, how, and when?
    That is indeed the problem when opinions become a religion, and one such as you would not dare to question the factual incorrectness of what you utter in a public place.

    So how about it? You tell us how you can keep a lens design going, but use different glass.
    Tell us how Zeiss would be caught out by a supplier not supplying what they want them to supply when they themselves are their own supplier of glass.
    And you know do who it was who started making glass according to specifications?
    Because it sure sounds like you take the way you would do things, and assume everyone else must do it the same way too.

    Sure there is variability in Q.C. And not all Zeiss lenses (of one batch) are equally good. But all are within specs. No worries.
    There's nothing religious about it, i.e. it's not a matter of believe, and of believe only. It's the result of being professional about what you do.
    Quote Originally Posted by Q.G. View Post
    Yes, there certainly is something like cheaper glass. Depends on how strict your specs are, and how close you want it to be to specification.

    The advent of computers in lens design meant more glass being used, not less.
    The more glass, the more complicated the calculations. Those modern 1,000 element IF AF lenses we have today would not have been possible if they too had had to have been calculated using a mechanical desktop calculator. Now we see nothing but such thingies.

    Anyway, the thing still is that Steve was right: most Zeiss lenses for Hasselblad (and Rollei) have remained unchanged since they were first introduced.
    The few other ones weren't changed either, but replaced by better ones. Despite you believing so, not something a manufacturer would keep a secret (wouldn't make sense to hush something like that up, would it?). So, for instance, a Tele-Tessar was replaced by an Tele-Apotessar, another Tele-Tessar was replaced by a Superachromat, etc.

    One exception: the Biogon was recalculated 'recently' (a relative term). True to Zeiss, the new one is just as good (though different) as the old one. But not better, showing that even though computers made things possible that weren't before, they did now what they were doing 60 years ago too. (But pointing out that professionals know their stuff doesn't sit well with you, does it? )
    Quote Originally Posted by fdisilvestro View Post
    I think that the Biogon formula was changed for environmental reasons, not because of cheaper glass. As fas as I know, the new formula is lead-free.
    Quote Originally Posted by Q.G. View Post
    Don't forget that Zeiss sell products at a price reflecting that those are of uncompromisingly high quality. And that people happily (well...) pay that price. So they are doing pretty well.
    So i don't know about that pressure... what pressure?
    So as I originally said, ZEISS did not make any optical changes on almost all the Hasselblad [and Rollei] lenses.

    I did not say a word about Sigma or any other companies.


    Thank you, Q.G. and fdisilvestro, for jumping in and filling in the details. I do not have the time to do research that others did not do due diligence and merely shot from the hip. BIY, it is better than use a viewfinder than shooting from the hip while taking photographs, not just posting in internet.

    Steve
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  4. #124
    Sparky's Avatar
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    I hope all misconceptions have been cleared up now...(!!!)
    That's another problem with the internet - spending hours arguing a misunderstood concept... oh well..

  5. #125
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    Quote Originally Posted by Sparky View Post

    As for your more pointed question - well... I think it would be a fairly simple thing to adjust a lens formulation for a drifting refractive index... I mean - just change the curvature of the corresponding element and run the calculations through the whole design and go back and forth until you have a winner. I don't think there's any huge mystery to the science and art of lens design. All I'm trying to say is that they probably have a strategy for dealing with aberrations (no pun intended!) in their supply chain. And they're probably also highly motivated to cut costs and improve profit margins. They're a company after all. Is that not what companies DO? It seems reasonable to me.
    Ok, I have to chime in on this one.
    What you say is ridiculous, to anyone who has manufacturing experience. I have experience in both the production side and the QC side.
    You betray your ignorance in these statements. You think that it's as simple as just recalculating and just changing the curvature of an element: what do think that costs?

    I have seen a lot of expensive manufactured products get scrapped because they are out of spec. Sometimes a product can be reworked until it is in spec., sometimes it can get a variance, but usually it is scrapped. It's just not worth it to mess with it. It's quicker, easier and simpler to remake the product, than to mess with fixing discrepant product. To start custom making batches of parts to match discrepant material is to introduce variables no one wants. It introduces uncertainty and creates hassles. Why spend a bunch of time and effort to make something that's not as good as it's supposed to be?
    I've scrapped orders with 2% bad parts, because the time taken to sort good from bad cost more than they were worth.

    I have seen instances where discrepant materials have had to be used for some reason, and I mean material out of spec enough that the difference was not just academic. Every time was a huge hassle, and every time was due to a failure somewhere. It usually resulted in making little or no profit or losing money on the order. It was always the result of the failure of someone to do their job. It was chronic in poorly managed companies, and non-existant in well managed ones.

    I once was ordered by my boss to make an adapter for several thousand knobs that a purchaser had ordered without realizing they wouldn't fit. The adapters could not exceed 7 cents cost because that was the price differential between the right knobs and the wrong ones. All my other work came to a halt while I came up with something that would work, along with an engineer to okay it, and all this was under the table. No part number, no job number, setup time slopped into other jobs, material provided by purchasing who stole it here and there from other jobs. I produced the adapter, the purchaser and his boss got their asses covered, my boss and the engineer got a favor to call in on purchasing, and I got the fun of busting my ass to make up for lost production.
    That's no way to do things. And that was a poorly managed company.

    Any time you change one thing it changes other things. And no one wants those headaches. If refraction is out, what about dispersal, and every other characteristic?

    Materials are seldom a major part of the cost in manufacturing an object. Overhead and labor will typically represent a far greater amount of the cost of a product. The labor and delay involved in recalculating and resetting a machine will exceed the savings from using the discrepant glass. I would think, but don't know, that rejected glass could be remelted and brought to spec, at least in some cases.

    Here is what would be required at a minimum to use the discrepant material, and don't forget every stage is going to require paperwork to be generated, reviewed, handled, signed off on, and archived.:

    >QC discovers the glass is discrepant, and rejects it.

    >If not scrapped outright by glass manufacturing, it goes to a Material Review Board, usually composed of representatives of manufacturing, engineering and QC, to determine cause and course of action.

    >MRB (or whatever Zeiss calls it) decides to use the material.

    >Engineering recalculates optical formula and produces new production spec.

    >Spec. is reviewed and approved by optical and mechanical engineering, then checked and approved by quality control. Then checked and accepted by manufacturing. Then signed off on by management of those departments, then by higher management, possibly to VP level.

    (This a minimum. There are actually quality engineers, manufacturing engineers, production planners, and others whose input and work will be needed. The delay may create a bottleneck in getting other materials produced, and may make the whole idea unworkable. Recalculating takes computer time, in addition to engineering time, away from other projects, and disrupts projects underway.)

    >Manufacturing modifies machine setups to produce parts to modified spec.
    First article part (aka "First good part) is produced for each phase of production. First articles are checked and rejected or accepted.

    >After acceptance, the limited run begins, each step in turn. At the conclusion of the run, with parts accepted to modified spec, all machines will have to be set up to original spec. if more of the same part are to be made right away. Unless of course, the next batch of glass is somehow out of spec, and the process will have to be repeated for that batch. Unless it's identical to the first out of spec batch.


    Zeiss has been making optical glass for a very long time. They know how to do it. They know how to hold tolerances. They know how avoid problems. They did not get where they are by screwing around with non-conforming materials.

  6. #126
    Sparky's Avatar
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    Trolls. never said that. I'm sorry you took it wrong.

  7. #127
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    NOBODY ever said it was cheap or EASY to change a lens design. When I said 'simple' I did not mean to imply any of the following concepts: 'inexpensive', 'fast', 'easy'... when I say the word 'simple' I mean 'simple in concept' - well I explained PRECISELY what I meant already. CLEARLY you have to re-tool, reformulate everything, including all the steps you imply above. I'll at least give you credit for going to town on your descriptions (!).

  8. #128
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    Well, first you said that you "guarantee" there were lots of times when Zeiss got lens blanks with out-of-spec refractive indexes. You didn't, by the way, explain how they got to the point of being made into blanks before the discrepancy was discovered, much less how they got shipped from the glass plant that way. If they were from an outside vendor, how would they have even made it through the door?

    Materials go through final inspection before being shipped, and go through receiving inspection before being accepted, and if they are discrepant they get sent back. Literally. I have stuck "Return To Vendor" signs and rejection tape on scores of pallets of material before locking them in a secure holding area. I worked for a company that in 1977 sold over a million dollars worth of product to Kodak. Kodak's receiving inspection sent them all back, freight collect, with reports describing every issue they found. Why would Zeiss accept out of spec materials from an outside vendor?

    Zeiss' grinding shop might well accept material from their own glass plant without reinspection, because they know they can trust the glass plant's QC. As the nature of optical inspection is quite exacting, and Zeiss pioneered much of the entire precision optical industry, I see no reason for such an obvious blunder to occur. I've worked with native Germans in manufacturing, and I can say from experience, they do not tolerate sloppiness. Their work is precise, and their methods are precise.They take personal pride in their work, and a blunder of that sort by an inspector, of all people, is utterly unacceptable. So for it to happen, as you say, "lots of times"? I doubt it.

    You never explained what the basis is for your assertion regarding out-of-spec blanks, except as far as I can tell, something along the lines of it must have happened. I imagine out-of-spec material was made at times; whether it got to the grinding shop, much less into the final product, is something else altogether.

    After your assertion that Zeiss must have gotten out-of-spec glass, "lots of times", you in another post said you think it would be a fairly simple thing to adjust a formulation for a drifting refractive index. I took that in conjunction with your prior post to refer to discrepant materials. The word "drifting" implies imprecision. If you meant "changed", based on a glass formula having permanently changed, that's something else. But that's not how it reads to me.

    My post was detailed in order to show that is not a fairly simple thing to do what you suggested. I don't see how it's simple-in-concept unless you are saying that it is in comparison to an extensive re-formulation based on a change in the glass. Even then I don't think it's all that simple. A changed refractive index is one possibility in a changed glass, but what of all the other properties that can change?

    Maybe a slight tweak is possible in response to a slight change in the type of materials used, but if that's what you meant, you sure could have made it more clear.

    And one more thing- I ain't no troll! :rolleyes:
    Last edited by lxdude; 05-02-2010 at 03:21 AM. Click to view previous post history. Reason: clarity

  9. #129
    Sirius Glass's Avatar
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    Sparky,

    Consider yourself will spanked.

    Steve
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

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