Some Comments about Tessar, Sonnar and Elmar (Part One)

This Artical is originated from Wah of Contax Club:

小弟唔係光學專家...........不過既然係 Leica 野就用番 Leica 界權威 Erwin Puts 既言論討論一下.......

1. Leica M-lenses

http://www.leica-camera.com/imperia/md/content/pdf/msystem/49.pdf

在 Page 42, "The first lens used for the Ur-Leica had a focal length of 42mm. Commercial models (from 1925) were fitted with the Anastigmat/Elmax f/3.5/50mm. This design had 5-elements, presumably to avoid patent conflicts with the Zeiss company........."

小弟對於 Kino-Tessar 50mm 既質素當然未能理解.........不過世界上就真係一樣唔知係造福人群定係遺禍人間既發明.........就係叫 patent

想當年 Elmar 50/2.8, Elmar 50/3.5 既設計都係以 Tessar 為藍本.........不過光圈位置就與 Tessar 不同, Leica 的設在第一組與第二組之間, Tessar 的就在第三組與第四組複合鏡片之間. 對於此設計, Erwin Puts 有此評論:

(同樣 Page 42) "The Elmar f/2,8/50mm was introduced in 1957, almost 33 years after the Elmar f/3,5/50mm. In its day, the Elmar f/2,8 was famous for its very good image quality in the center. It was also slightly ahead of perennial competitor Zeiss
with the Tessar. The different position of the aperture (between the first and second element) was the main advantage of the Elmar. On test the Elmar performs acceptably, at full aperture with a low overall contrast and clearly rendered fine details with smooth (more accurately: soft) edges..........."

當然 Elmar 係不少 Leica fans 既摯愛........由其以 Red-scale version 最受追捧! 是由於使用稀土玻璃之緣故..............小弟則相信, 以 Tessar 此相對簡單之設計下, 對於鏡片組裝與鏡片質素上既要求其實更高, 任何廠家 (Voigtlander, Nikon, Canon) 只要有誠意制作個人覺得質素不會相差太遠.

而當年的 Voigtlander (未被 Zeiss 收購前)既 Skopar 都係用 Tessar 既一套...

http://www.taunusreiter.de/Cameras/Bessa_RF_histo_dt.html

不過.........既然 Leica 係製造 Tessar 一類鏡上有如此獨門秘方..........小弟就不知如何解釋其後推出既 Elmar-M 就用回 Tessar 既設計..........或者係 original Elmar 既設計生產成本高昂?

另外一個解釋係..............Tessar 係 2002 年慶祝 100 歲生日

2. 至於1933 年推出既 Summar 50/2 (參考 LEICA LENS 不朽之名玉 203, Page 104), 其根本 design 就是 Double-Gauss, 以當年 35mm 相機市場計, 由於 coating 問題, 以 Double-Gauss 所設計既大光圈鏡由於玻璃介面比較多既關係 (如 Summar, Xenon, Summitar 一類) 一直被 contrast 較高, Flare 及 玻璃介面比較少的 Sonnar 50/2 及 Sonnar 50/1.5 所比下去. 不過以市場先決原則, 就算性能上是以 Elmar design 佔優, 但又怎可錯過大光圈標準鏡的市場 (以當天 ISO 50 為高速菲林計............)