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[nikomat 33308] Re: W nikkor 35/2.5
日浦Ｒです。
At 2002/08/30 16:43:21 Kazuhiro Igeta wrote:
> > "Tomosuke Takanashi / 高 梨 智介" wrote:
> >
> > おや、レンズ一本だけなんですか？(^^;
> > スーパーアクロマート、写りはどうでしょう？
>
> こりは、なんすか?
>
> むかしスリービーチ光学という安物望遠鏡屋が
> こんな名前つかってたなあ。
> 関係ないとおもいますが^^;
この望遠鏡は，アポクロマートになりきれていないもの
だったように聞くのですが，ツアイスのスーパーアクロマート
というのは実は登録商標で，アポクロマートの上を狙った
4波長色収差補正のレンズのことです。
出来上がったガラスの特性を計測し，ロットごとに設計修正して
作るそうです。
今のところハッセル用のみで250/5.6，350/5.6（レンズシャッタつき）と
300/2.8(テレコンがセットになっており500/4.5になる。シャッタなし)
ってのがあります。
250/5.6だけは1972年の発売ですが350と300は最近の設計ですね。
300/2.8はたしか100本限定で300万円だったかな。
以下はツアイスの広報担当Freischerさんの説明です：
＃こういうの読んでると洗脳されるんですよね。。。
The Sonnar Superachromat 5,6/250 was introduced in 1972.
It was the result of years of optical calculations with
the goal to build a telephoto lens with a performance
that was only limited by diffraction. To achieve this goal,
chromatic aberrations needed to be corrected on a level
never before achieved in a telephoto lens. In other words:
The secondary spectrum had to be reduced below the
"Rayleigh limit". Apochromatic correction (developed by
Prof. Dr. Ernst Abbe at Zeiss in the 1880s) would not be
sufficient to achieve this goal. Something had to be done
which goes even beyond apochromatic correction:
Superachromatic correction. This level of correction was
envisaged and theoretically described by Max Herzberger
in the late 1950s, but he was unable to achieve it in
real world optical design. At Zeiss, Determann eventually
came up with a usable solution in the late 1960s.
Photo magazines that have seriously evaluated this
Superachromat 5,6/250 ever since came to the conclusion
that the Zeiss Superachromat is the best camera lens ever
conceived.
All of this is why my heart of a lens liking person loves
this 250 mm Superachromat. The NASA also loves it. And
since they used it in multi spectral camera systems
including infrared imaging channels, Zeiss T* multi
layer coating was not applicable with the Superachromat,
since that would have limited transmission for infrared.
So other measures had to achieve stray light control with
"only" single layer Zeiss T coating. This fact, and the
very demanding manufacturing process (= only few could
be made back then) led Hasselblad to target it at
scientific applications.
In the meantime Zeiss has more than doubled the manufacturing
capacity for this lens. From a background of quantities there
is no reason any more to limit this lens to NASA, scientists,
and myself. However, there is one more consideration: Contrary
to popular belief not all lenses with the same focal length
produce the same depth of field at the same aperture! A typical
example is the Superachromat 5,6/250: It produces extreme
sharpness (250 linepairs per millimeter)at the plane of best
focus. But slightly off (which may be caused by photographer's
focusing error, film position error, curvature of film, humidity,
registration error of mirror or focusing screen, magazine wear,
to name just a few), the sharpness drops dramatically. It can
drop even below the levels the sharpness of a Sonnar 5,6/250,
or the one of a Tele-Tessar 4/250. In other words:
The performance of the Superachromat is extreme, but nervous.
It requires advanced technique on the part of the photographer
and also well aligned and maintained equipment, to actually
utilize the full potential of this lens. Once all this comes
together, the Superachromat shines. No other lens in the world
ever gave me fine details with this clarity!
This lens is perfection for perfectionists.
Photographers who prefer to engage less with these aspects may
even achieve "better" results with the normal Sonnar 5,6/250.
-- Kornelius J. Fleischer , October 20, 2000; 04:52 A.M. Eastern