[rollei_list] Re: OT: Leica vs. Zeiss
- From: Eric Goldstein <egoldste@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 19 Nov 2009 08:19:12 -0500
Hi Frank -
I think we have pretty much exhausted the idea of the lack of validity of
magazine tests over years of past discussions... it is well known that they
are not statistically valid, that the methodologies vary widely from one rag
to the other, that the testers are not independent voices without monetary
motivation, etc etc etc. Still, a report that a lens is the most highly
corrected is worth knowing, just as a report that a lens is the worst ever
tested would be.
The CV 50/.5 is a true Heliar design, as the block diagram on the lens
barrel attests. A curiosity about this lens is that is it designed to it's
true lens speed (best corrections at f/3.5) which is a real rarity.
Eric Goldstein
--
On Thu, Nov 19, 2009 at 2:11 AM, Frank Dernie
<Frank.Dernie@xxxxxxxxxxxxxx>wrote:
> I am sceptical of any test which does not test a statistically valid number
> of units. Experience and hearsay leads me to believe that there is very
> considerable sample variation in reasonably priced lenses, particularly
> those which have a very large number of elements such as zooms, especially
> those with image stabiliser units also. The precision needed in axial and
> radial location of the elements is extremely high and I do not think it is
> achieved in general production. These lenses are cheaper due to less quality
> control, IMO. If the lenses sent for review are hand selected the consumer
> will perhaps be tempted by the writers enthusiasm. If the lens he/she buys
> does not perform as well as the test item the vast majority of consumers
> will not notice, IMO.
> This certainly was the way it went in the HiFi business during the short
> time I was involved.
> I suspect those lenses with the minimum number of elements commensurate
> with the performance requirement, with high precision mounts correctly
> temperature compensated if possible/necessary and with a high degree of
> post-manufacture quality control are probably the good ones, and
> reassuringly expensive.
>
> WRT the 50mm f3.5 CV lens, firstly I am not sure whether the lens is
> actually a Heliar by construction or by marketing, and also in this era it
> can hardly be difficult to produce a spectacular lens this slow.
> cheers,
> Frank
>
> On 18 Nov, 2009, at 22:11, Richard Knoppow wrote:
>
> >
> > ----- Original Message ----- From: "Eric Goldstein" <egoldste@xxxxxxxxx>
> > To: <rollei_list@xxxxxxxxxxxxx>
> > Sent: Wednesday, November 18, 2009 1:55 PM
> > Subject: [rollei_list] Re: OT: Leica vs. Zeiss
> >
> >
> > Curious where this information comes from?
> >
> > BTW if I'm remembering right the CV 50/3.5 Heliar tested in at least
> > one of the testing mag/rags as the most highly corrected lens of all
> > the 35 mm gear they ever looked at...
> >
> >
> > Eric Goldstein
> >
> > --
> > Me too, this is just not the way lenses are designed. While the glass
> can be a major cost item there are others, such as difficult to make
> surfaces that result in high reject rates and cemented surfaces that require
> a lot of hand work and extra steps. Also, some glass has excellent optical
> properties but is very difficult to work with so its used only when it can't
> be avoided.
> > Some glass types are no longer made because of environmental
> considerations. An example is that arsenic, which had been used as a
> clarifier for generations, had to be eliminated. This is one reason that
> many lenses were re-designed in the recent past. Not to improve them but to
> make it possible to continue making them.
> > In general, the Heliar type is not capable of being corrected as
> highly as some more complex generic designs. While some very good Heliar
> type lenses have been made (by Kodak for instance) designers have mostly
> found that other arrangements offer better opportunities.
> > I also add that I am very skeptical of magazine testing.
> >
> > --
> > Richard Knoppow
> > Los Angeles, CA, USA
> > dickburk@xxxxxxxxxxxxx
> > ---
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