（可能显幼稚）改口请教：RF 50mm镜头，有无可能改成M42口？

Onlystone

dodonaomik 发表于 2018-9-26 18:02
只能往上走，不能往下走

是这个意思，不是完全不能往下走，也不是完全都可以往上走，大原则是往上走，，，，，，如果往下走也行，小改就行，，，搓口，，，，，，也不是完全可以往上走，比如有的卡口法兰距只差了1mm，做不了这么短的转接环

dachuan

旁轴镜头能否改为单反镜头，取决于镜头后镜片的外沿在无穷远焦段时是否会影响单反相机反光板正常翻起，也就是常说的打板，现实中有的旁轴镜头是可以改为单反镜头并无穷远合焦的，也有很多则不行，旁轴镜头与单反镜头的设计思路不同，故此。另外，即使镜头具备改单反镜头的物理条件，也需要有足够的机械常识和机加工能力。

dodonaomik

我很不死心，想把资料“一网打尽”，到WIKI处，搞到Flange focal distance的一些资料，基辅的一些资料


Kiev 35 mm cameras[edit]

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Kiev 4A rangefinder camera

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Kiev 4 with Jupiter-8M lens and original camera case

Kiev also produced several 35 mm film rangefinder cameras which were clones of the pre-war Contax II and Contax III cameras, and a range of 35mm SLR cameras.

After the war had ended, the Soviet Union demanded new sets of Contax tools from the original toolmaker in Dresden and then ordered a fair number of trial cameras to be made with Zeiss trademarks and coated lenses from these 1946 in postwar East Germany. With this successful, everything together with German instructors were transferred to Kiev. Missing specialists were in a few cases recruited in West Germany. Any still available parts went in the same direction. In fact, removing the front of some very early Kiev II cameras, one could see that the metal was originally stamped with the Contax name, then pressed out and re-stamped as Kiev.

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Kiev 15 Tee

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Kiev 19 body

Kiev rangefinders retained the same lens mount as the prewar Contax rangefinders and the lenses can be interchanged. The cameras went through a few minor modifications to become the Kiev III and eventually Kiev 4. There was also a Kiev 5 with a modernized upper part with integrated meter. Attractive, though poorly made and unreliable, its production was soon terminated. The other models were kept in continually downgraded production until the 1980s. The number of Kievs vastly exceeded that of the pre-war Dresden and post-war Jena and Stuttgart Contaxes.

sunny9494

法兰距相差太大，没戏。
有个另类方法，加减焦镜，就是加凹透镜

dodonaomik

基辅相机

根据WIKI介绍，这个系列的相机，就是战前Contax II 以及 Contax IIIの克隆与复制。
基辅2算是元老，经过几个小小的调整、微调，
就有啦基辅3、基辅4.


基辅相机总数，远远逾越啦战前Dresden/德累斯顿   以及   
战后 Jena/耶拿 、 Stuttgart/斯图加特  所生产的康泰克斯相机的数量

sunny9494

首先，改动光学结构肯定会影响画质。
为了玩玩儿不管画质的话，有两个思路：
1-在镜头后口加转接镜，就像以前有过NFD转EOS的制式转接环一样，镜头和卡口之间加一组凹透镜组延长法兰距。日本有专业厂家出品这个环，质量还是可以的。
2-镜头前部附加凹透镜，以延长后距。

dodonaomik

以前，对旁轴稀里糊涂的有所概览，
今天看到dachuan老师精细入微的评述，引起了我的兴致：旁轴鸡儿，英文叫啥？到底应该咋理解这个鸡儿比较好？
由此，摘来拉下面的资料
____________________________________________




A rangefinder camera is a camera fitted with a rangefinder, typically a split-image rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most varieties of rangefinder show two images of the same subject, one of which moves when a calibrated wheel is turned; when the two images coincide and fuse into one, the distance can be read off the wheel. Older, non-coupled rangefinder cameras display the focusing distance and require the photographer to transfer the value to the lens focus ring; cameras without built-in rangefinders could have an external rangefinder fitted into the accessory shoe. Earlier cameras of this type had separate viewfinder and rangefinder windows; later the rangefinder was incorporated into the viewfinder. More modern designs have rangefinders coupled to the focusing mechanism, so that the lens is focused correctly when the rangefinder images fuse; compare with the focusing screen in non-autofocusSLRs.

dodonaomik

SLR system剖切面【偶然看到这张生动的图片，感觉比较原汁原味，舍不得“扔掉”，一并贴出】:



1:/Front-mount lens (four-element Tessar design)
前口




2: Reflex mirror at 45-degree angle
反光镜






3: Focal plane shutter
焦平面快门【shutter~本义有点翻折板的意思】






4: Film or sensor
感光器/传感器   抑或交卷





5: Focusing screen
聚焦屏






6: Condenser lens
聚光透镜




7: Optical glass pentaprism (or pentamirror)
光学玻璃五棱镜




8: Eyepiece (can have diopter/屈光度   correction ability)

目镜/视窗

dachuan

旁轴镜头与单反镜头的本质区别，说白了就是单反镜头要考虑在镜后留出反光板翻起的空间而旁轴镜头则无需考虑，所以，以135画幅的50毫米标准镜头为界，长于50mm焦距的中长焦镜头，旁轴与单反镜头的光学结构区别不大甚至没有区别，而短于50mm广角镜头，旁轴镜头几乎可以任意设计，比如师奶超级安古龙或是蔡司标刚。。。而单反镜头则要考虑在镜后留出三四十毫米的反光镜翻起空间，因而无法采用传统光学思路设计它的广角镜头，于是便有了逆焦结构或叫反望远结构，如蔡司的迪斯塔刚之类，这类单反广角镜头采用类似猫眼门镜与标镜组合的特殊光学结构，使其在具备广角视野的同时，镜后仍有足够的反光镜翻起空间。

那么，作为分界线的50mm标准镜头究竟是什么情况呢？不知大家是否注意到，绝大多数135单反相机的法兰距都在40-50mm之间，为什么？因为这个距离刚好处于传统结构50mm镜头的镜后距范围，所以，同样采用传统设计的50mm标准焦段范围的旁轴镜头和单反镜头，有可能具有相同的光学结构和物理参数，意即其存在可以改为单反镜头的基本条件，但假如是采用了多片多组的复杂光学结构比如双高斯普兰娜之类那就不好说了。。。所以，有的可以有的不可以。

法兰距是一个机械参数，它和镜头的光学物理数据没有直接必然关系，例如50mm天塞旁轴镜头与具有相同光学参数的单反镜头法兰距就相差甚远。如果打算用转接环转接镜头，法兰距的确是一个重要的判断数据，而如果是彻底的改口，我们只需关注镜头在无穷远焦点时，其后镜外沿是否打板就可以了。

dodonaomik

Flange focal distance位于【40，50】这个区间段的，确实比较多啊！达到啦34种！