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Re: [OM] Questions, questions...

Subject: Re: [OM] Questions, questions...
From: Ingemar Uvhagen <ingemar.uvhagen@xxxxxxxxxxxxxx>
Date: Tue, 14 Jul 1998 10:26:50 +0200
Cc: olympus-digest@xxxxxxxxxxxxxxx

I bow and thank thee for the information!
As I always say: Learning all the time.

Warren K.:

Thanks to you too!

Kennedy wrote:

> As usual with these acronyms it is no more than marketing hype!  :-(
> You are interpreting "dispersion" as "scattering", which is exactly the
> trap that the spin doctors at Olympus and Canon hoped you would fall
> into - hence it makes the glass seem almost intuitively superior.
> Dispersion is the change of the refractive index of the glass with
> wavelength, so it is the ability of the glass to split white light into
> its component colours or, equally importantly, the ability of the glass
> to correct the chromatic aberrations of other elements in a particular
> lens design.
> Armed with this knowledge you can see that in some cases ED and UD glass
> can actually be less effective at correcting lens aberrations than plain
> old beer bottle glass!
> Fortunately the designers at Olympus and Canon are a separate group from
> the marketeers, and only use this type of glass where it is needed.
> Needless to say, one day one of the spin doctors wanted to get some new
> differentiater between Canon or Olympus and their competitors and took a
> stroll down to the workshops to ask if there was anything special they
> could say about their optics.  One of the engineers was heard to say
> "this needs a low dispersion element to do the job right" and the
> marketing man drew up the publicity without understanding what it meant.
> Couldn't happen?  If it didn't I might have had a less stressful time at
> work today!  :-(

Warren Kato wrote:

> Well, the problem here is one of translation, not of knowledge.  The lens
> designers pick whatever glass best fits their design, goals, cost/performance
> ratio, etc.  There are many type of glass.  One of the first of the new
> "glass" types was calcium fluorite, which allowed designers to make better
> apochromatic telephoto lenses.  Apparently there are dozens of types of glass
> used in the design of lens, each with its own index of refraction for each of
> the wavelengths that film is sensitive to, dispersion index, cost, etc.
> After the lens designers do their brilliant work, they turn it over to the
> advertising guys.  They may not know a Zuiko from a ziggurat but they know
> they have to sell by inventing catchy phrases.  Various Olympus brochures use
> words such as: special optical glass, extra low dispersion glass, high
> refractive index glass, apochromatic type elements.  Hence the terms UD, ULD,
> ED etc.  IMHO, just listen here and look at test reports, and this will help
> find the best lens.

  Ingemar Uvhagen
  Gislaved, Sweden

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