不是F4，是0.4ft Mark的所谓非球面版本。

Pentax SMC K15/3.5AL VS A15/3.5  
      
溯源：

The following is based on research done by Dario Bonazza and published in Spotmatic magazine, number 29 from July 2001.

At Photokina 1972 Pentax and Carl Zeiss showed prototypes of a 15mm f/3.5 rectilinear lens with remarkably similar optical designs. In fact, the only noticeable difference was that Zeiss' lens employed only spherical optics while Pentax's made use of one hybrid aspherical element. In 1974 both prototypes became production lenses. Pentax's SMC TAKUMAR 1:3.5/15 was virtually identical to the prototype from 1972 whereas Zeiss's lens used the same optics but employed floating elements, probably for improved close-performance.

Here the story gets really interesting and a bit unclear. Pentax was of course proud of their aspherical optic, and did mention it in some early lens brochures. However, shortly afterwards they decided that the production of the aspherical element is too expensive, and started developing an alternative optical formula based solely on spherical surfaces. The aspherical element was no longer mentioned in any Pentax publication, but until the new optical design was ready, all 15/3.5 lenses were based on the original design. The first 15mm lenses based on the new design were produced in October 1975, about four months after the introduction of the K-mount. For a short period of time, screw-mount and K-mount lenses were produced in parallel, so Dario believes that a total of about 900 Takumar 15/3.5 lenses were produced, 400 of which employed aspherical construction. On the other hand, only about the 100 of the SMC PENTAX 1:3.5/15 were aspherical. The remaining SMC PENTAX 1:3.5/15, all SMC PENTAX 1:3.5 15mm and all SMC PENTAX-A 1:3.5 15mm are based on the spherical optical formula.

In order to compensate for the lack of aspherical surfaces in the second optical design, Pentax changed several of the optical elements, including the size and curvature of the front element. The exact differences or measurements, however, are not known.

发现：

lenses with the name SMC PENTAX 1:3.5/15 and a distance-scale that includes a 4-foot-mark have one aspherical element.

咳，这么多，咱没这么大的棚，拍不下得

2835其实有得，只不过咱觉得它不长不短不高不矮没摆进去。

1535嘛~~

咱是P家人，咱拼的是厚道，咱有得借有得用的时候从来不挑。

A24/2.8，A50/1.2，A50/1.4，A50/2.8，A85/1.4，A100/2.8，A135/1.8，A200/2.8，A200/4。

啥时候咱的防潮箱上能贴上这样一张清单，咱就满足了。

[玩宾得的猪头 编辑于 2007-08-13 21:00]

QIUJZ兄，你一定记错了吧，我怎么可能是资深

借的东西，也来亮亮骚。

大盒子就是俺的下一个目标！

K100D

18-55套头

大名远扬……有这种事么……向来没跟人吵架啊!!

你是最近最大的FB份子

太FB了这个....现在流行叠罗汉啊~~~~


靠，漂亮....胡子那边说MZ3跟43LE是绝配，反正不管怎么整，43LE就是绝配的一部分.....

越看越喜欢，结果周末顺道就折腾了一个43LE回来~~~~

228被狗狗叼走了？

简单啊，累包装盒就是了

严重期待新版星际叠罗汉

灰飞烟灭之后可以用da*重筑，万里长城永不倒