Hi Carlos,
You have some very interesting information here. I appreciate the
summaries, all in one place.
I have been experimenting with a Ross London lens dated around 1890, but
designed much earlier. I don't know the specific design details, but it
appears to be matched front and rear elements. The lens surprised me with
its sharpness, and its color-rendering, given that it was designed before
color images were even a consideration. The lens is of 8" (200mm) focal
length, with Waterhouse stops from f/16 to f/64.
Here is the lens:
http://gallery.leica-users.org/v/OldNick/Ross+Lens+2.jpg.html
Here is an image made at f/16:
http://gallery.leica-users.org/v/OldNick/Mocking+Bird.jpg.html
Jim Nichols
Tullahoma, TN USA
----- Original Message -----
From: "Carlos J. Santisteban" <zuiko21@xxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxxxx>
Sent: Friday, January 21, 2011 11:49 AM
Subject: Re: [OM] Heliar (Was: 50mm 1.8 (Re: Hoarding & Varimagni))
> Hi Mike, Andrew and all,
>
> From: usher99@xxxxxxx
>>(previously took 8 to 10 elelments to achive that reduction in
>>aberrations)
>
> In fact, the Planar / double Gauss formula is somewhat earlier, from the
> late 1800s... but without anti-reflection coatings, so many air-to-glass
> surfaces made it unfeasible because of flare. This was the reason behind
> the
> Tessar and Heliars -- a development of the classic triplet instead of a
> high
> performance design from the scratch, in order to keep the three-group
> configuration for good flare resistance.
>
> It goes without saying, a Tessar (and surely a Heliar too) with modern
> coatings is *extremely* flare resistant...
>
>>I believe these
>>types of lenses are aberration, not diffraction limited for the most
>>part.
>
> Stop down enough, and any design will be diffraction-limited :-) I can see
> some edge degradation on Tessars wide open, but not _that_ terrible... Not
> everything about a lens is MTFs and lp/mm, I do like the Tessar's
> rendering
> a lot.
>
>>lens design of the CV 75, but it didn't register. It seems to have
>>rendering qualities similiar to the original Heliar
>
> Really have little experience with it (and none with the original) so I
> can't tell for sure...
> <http://www.flickr.com/photos/zuiko21/3559972756/sizes/o/> (quick and
> dirty
> scan)
>
>>but I don't
>>understand the naming of it at all. Perhaps it is marketing decision.
>
> I think only Zeiss uses the optical design as the key for naming:
> Distagon,
> Biogon, Tessar, Planar, Sonnar... Nowadays, Leica names just mean the
> maximum aperture:
>
> Elmar: F3.5 - 4
> Elmarit: F2.8
> Summarit: F2.4 - 2.5
> Summicron: F2
> Summilux: F1.4
> Noctilux: F1.2 or faster (currently 0.95!!!)
>
> As for CV naming... it seems plain marketing to me, too -- the Heliars are
> the 12/5.6, 15/4.5 and 75/2.5, plus the new, classic design, limited
> edition
> 50/2 and 50/3.5.
>
> Update! There's the new "Heliar Classic" 75/1.8... I've found a schematic
> of
> it, and it seems yet another formulation of the classic Heliar (as
> suggested) with a doublet replacing the negative central element:
> <http://www.cosina.co.jp/seihin/voigt/v-lens/v-l-m/75-1.8/75-1.8.jpg>
>
> But the non-classic designs are just double-Gauss (75/2.5) or mild
> retrofocus (12 & 15mm):
> <http://cameraquest.com/jpg4/vm-12.gif.gif>
> <http://cameraquest.com/jpg4/vm-15.gif>
>
> And *very* good, extremely compact lenses they are...
>
> On the other hand, there seems to be a pattern with some of the rest:
> Nokton
> is for high-speed lenses (F0.95 - 1.5) while Ultron is for lenses around
> F2.
> Most lenses F2.5 of slower are called Skopar.
>
> Speaking of Nokton... I'm impressed with the performance of the 50/1.1.
> Most
> super-speed lenses are mediocre performers and/or complex designs (the
> very
> nice Canon FDn 50/1.2*L* has 8 elements, with some aspherical surfaces)
> but
> the Nokton is a run-of-the-mill 7 element-6 group formula with no
> aspherical
> surfaces, no LD elements... like most 50/1.4s on this planet -- usually
> much
> poorer performers!
>
>>APO dosen't seem to mean as much anymore either.
>
> Even without being corrected for *three* colours of the spectrum, that
> usually means better colour correction. IME, modern Tessars (and the
> Russian
> Tessar-like Industar-61 L/D) are very good at this. And back to CV, the
> APO-Lanthar 90/3.5 (another double Gauss) is very, very, very, very
> good --
> not that it's a difficult lens to design, but this one performs just
> great.
> Did I say it's very good? :-)
>
> So far, the only lens with the honour of being CA-free, at least within my
> measurement / observation range, also comes from CV: the tiny Skopar
> 28/3.5.
>
> From: Andrew Fildes <afildes@xxxxxxxxxxxxx>
>>I just bought a modern Cooke Triplet - the Perar Super-Triplet - a hand
> built run of
>>200 by MS Optical -
>>
> http://www.japanexposures.com/shop/product_info.php?cPath=33&products_id=423
>
> Yes, I know them! They make interesting mount adaptions of classic
> lenses...
>
>>This one was an attempt to demonstrate that a Cooke Triplet, properly
> designed and
>>with modern coatings, can exceed the performance of a Tessar design.
>
> This is getting *very* interesting... as I mentioned above, a "classic"
> design may perform much better than expected thanks to modern technology,
> but I'd love to see your results with it...
>
> Cheers,
> --
> Carlos J. Santisteban Salinas
> IES Turaniana (Roquetas de Mar, Almeria)
> <http://cjss.sytes.net/>
> --
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>
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