The Focusing Helicoid Disassembly of the Carl Zeiss Jena Flektogon 25mm f4 M42 Zebra Version

2026/7/5

One of the first issues I noticed after acquiring this lens was that the focusing ring was extremely stiff. At certain points, it required considerable force just to turn it. Considering that this is a 50-year-old lens, it's no surprise—the original helicoid grease inside the focusing mechanism has most likely dried out over the decades. Instead of providing smooth lubrication, it has become a source of resistance.

Following the previous article on rear-end disassembly, this installment covers the disassembly, cleaning, and re-lubrication of the focusing helicoid. The first step is to remove the entire optical assembly. Looking from the rear of the lens, once the aperture linkage, aperture ring, and related components have been removed, the retaining ring that secures the front optical assembly can be unscrewed. The complete optical unit—including the front lens group, aperture assembly, and rear lens group—can then be lifted out from the front of the lens, leaving only the focusing helicoid behind.

這顆鏡頭入手之後，令人困擾的問題之一是對焦環很緊，有些位置甚至需要非常用力才能轉過去，畢竟是50年的老鏡頭了，鏡筒內的潤滑油應該都乾掉了，原本潤滑的功能變成阻力。

接續上篇拆開後鏡筒之後，這次就來拆開對焦筒、清潔、重新潤滑。首先，要把整個鏡組取出，從後鏡筒觀察，光圈開閉連桿、光圈環等相關的零件拆除後，再將鏡頭前面的鏡組固定環卸下，即可將整個鏡組、光圈筒和後鏡組從前方取出，剩下的就是對焦筒了。

The retaining ring that secures the front optical assembly is the first ring adjacent to the lens barrel.
緊鄰鏡筒內的第一圈壓環就是用來固定整個鏡組


The focusing helicoid consists of three main components:
(A) The outer barrel, which supports the optical assembly and the aperture housing.
(B) The focusing ring, engraved with the focusing distance scale.
(C) The depth-of-field scale ring.

On the underside of Ring C, there are two metal tabs positioned 180 degrees apart. These tabs couple Ring C to Component A, and each tab is secured by two screws. After removing the four screws and lifting off the two metal tabs, Component A can be separated from the combined B + C assembly.

對焦筒由三個零件組成 (A) 固定鏡組和光圈筒的外筒 (B) 有對焦距離刻度的對焦環 (C) 有光圈景深刻度的環。C環的底部相對180度位置有兩個與A環連動的鐵片，每個鐵片有兩個螺絲固定，將這兩個鐵片卸下，即可將這Ａ環和B+C環分解。

Inside Ring B, you will find a set screw that secures the infinity focus position. After removing this screw, Ring B can be separated from Ring C. I first used WD-40 to dissolve and remove the hardened grease from the helicoid threads. Afterward, I cleaned away any remaining WD-40 with isopropyl alcohol. Once the threads were completely clean, I applied a thin, even layer of medium-damping helicoid grease before reassembling the three rings by reversing the disassembly steps. The focusing ring now turns exceptionally smoothly.

B環內部可以看到一顆無限遠刻度的固定螺絲，將這顆螺絲旋下，便可將B環和C環分解。我先使用WD-40清洗螺紋上已經乾掉的油脂，再用酒精將WD-40清除，最後在螺紋上一層中度組尼潤滑油，之後反向操作上述步驟便可將這三個環再組合起來，轉起來非常順手。









When threading Component A back into the combined B + C assembly, it is important to engage the helicoid at the correct starting position. After the two metal coupling tabs have been reinstalled, Component A should be able to travel all the way to the bottom of the B + C assembly, which corresponds to the infinity focus position. Finally, reinstall the optical assembly, the rear aperture control mechanism, the M42 mount, and the remaining components. With that, the restoration is complete.

當A環要重新旋入B+C環，須注意螺紋旋入的位置，當上述兩個鐵片固定後，A環需能夠到達B+C環的底部(也就是無窮遠的位置)。最後裝回鏡筒，以及後端的光圈控制機構相關零件、M42接環等，就大功告成了。

Rear Mount Disassembly of the Carl Zeiss Jena Flektogon 25mm f4 M42 Zebra Version

2026/6/4

Today, while cleaning the aperture blades of a Carl Zeiss Jena Flektogon 25mm f/4 M42 lens, I removed the front optical assembly and took out the aperture blades for cleaning. After carefully reinstalling the blades in their correct positions, I attempted to refit the aperture control cylinder, only to discover that it would not go back into place because it was being blocked by a small metal tab that actuates the aperture mechanism. It became apparent that the M42 mount at the rear of the lens had to be removed first so that this component could be detached before the aperture control cylinder could be reinstalled.

Since I was unable to find any videos or photographs online showing how to remove the M42 mount on this particular lens, I decided to document the entire disassembly process myself. I hope this record will serve as a useful reference for anyone attempting a similar repair in the future.

今天為了清理Carl Zeiss Jena Flektogon 25mm f4 M42 的光圈葉片，我拆了前鏡組，取出光圈葉片清理後，重新擺好葉片，再裝回葉片控制圓筒，發現裝不回去，因為有一個控制光圈葉片的金屬突起阻擋。看起來必須先拆鏡頭M42接環，才能將該零件移除才能安裝。由於網路上找不到相關的Ｍ42接環拆除影片或照片可參考，所以我就拍下整個過程，做個記錄與分享。


Carl Zeiss Jena Flektogon 25mm f4 M42 Zebra Version


This is the lens base after the front optical assembly and aperture blades have been removed. Once the aperture blades are correctly repositioned, the aperture-control cylinder can be reinstalled. However, at approximately the 8 o’clock position, there is a small metal protrusion that engages and rotates the aperture-control cylinder. This protrusion prevents the cylinder from being inserted back into place, so it must be removed first before reassembly can proceed.

這是前鏡組和光圈葉片取出後的底座，重新擺好光圈葉片，就可以放入葉片控制的圓筒零件，但在8點鐘位置有一個轉動葉片控制圓筒的金屬突起導致無法放入圓筒，必須先移除才行。



The rear of the lens features the common M42 screw mount, and at first glance there appear to be no visible screws for disassembly. In fact, the black base beneath the mount is an aluminum outer housing. To remove it, firmly hold the lens body and rotate the black housing counterclockwise. The housing will then unscrew and can be lifted off, revealing the internal mechanism underneath.

鏡頭底部是很常見的M42接環，外觀看不到任何可拆卸的螺絲。其實接環下方的黑色底座是一個金屬鋁外殼，先握緊鏡身，再將黑色的外殼以反時針方向旋轉，即可取下。



After removing the black outer housing, you will see a ring-shaped component. This part connects the aperture actuator pin on the M42 mount to the depth-of-field preview switch on the lens body, forming the mechanism that controls whether the aperture remains fully open or stops down. Once the single spring attached to this mechanism is carefully removed, the ring-shaped component can be lifted out, allowing access to the parts beneath it.

取下黑色外殼後，可以看到一個環形的零件，它連接了接環上的光圈頂針和鏡身的景深預觀鈕，是用來控制光圈「開/縮」的機構，將機構上唯一的彈簧拿下來後，即可移除這個零件。



After removing the ring-shaped component, you will see four screws located beneath the mount. Once these screws are removed, the M42 mount can be detached easily, providing access to the internal aperture mechanism and other components inside the lens.

取下環形零件後，就可以看到接換下方有四個螺絲，將這些螺絲旋起後，M42接環就可以順利拿下來。



Next, the metal linkage that directly controls the opening and closing of the aperture blades becomes visible. Attached to it is another spring, whose purpose is to keep the aperture blades positioned at the f-stop selected on the aperture ring. This spring provides the necessary tension to ensure that the aperture mechanism follows the setting of the aperture ring accurately and remains fixed at the chosen aperture value during operation.

接下來，真正控制光圈葉片「開/縮」的金屬連桿出現了，上面有另一只彈簧，是用來將光圈葉片固定在光圈環所選定的光圈值。



One end of the linkage extends into the lens barrel and connects directly to the aperture blade control mechanism. The other end features an L-shaped metal tab, which interfaces with the ring-shaped component removed earlier. Together, these parts form the complete aperture actuation system. Through the interaction of the M42 aperture pin and the depth-of-field preview switch, the mechanism ultimately controls the opening and closing of the aperture blades, allowing the lens to switch between full-aperture viewing and the selected working aperture.

連桿的一端是深入鏡筒內的光圈葉片控制機構，連桿另一端L形鐵片則是與先前拆下的環形零件連動，最終透過光圈頂針和景深預觀鈕完成「開/縮」光圈的動作。



By removing these two screws, the component that controls the opening and closing of the aperture blades can be detached. Once this part is out of the way, the aperture blade assembly and its control cylinder inside the lens barrel can be reinstalled without obstruction, making reassembly much easier.

拆下這兩顆螺絲，可以把控制光圈葉片「開/縮」的零件取下來，這樣鏡筒內的光圈葉片零件就可以順利安裝了。

I referred to mikeno62's video, Carl Zeiss Jena Flektogon 4/20 for Exakta, as a guide during the disassembly/reassembly process.

我參考了 mikeno62 的影片 Carl Zeiss Jena Flektogon 4/20 for Exakta

https://youtu.be/XkzOlicu1bo?si=cEWQ1F8tx5XDYN_p

MC Jupiter-9 85mm f2 and Sony A7C

2026/3/22






My third collectible Soviet lens is the Jupiter-9 85mm f/2 MC, a lens with a strong lineage tracing back to the pre-war Carl Zeiss Jena Sonnar 85mm f/2 made for Contax RF cameras. This particular copy was manufactured in the late 1980s and features MC multi-coating. Although the exterior shows heavy signs of wear, the optics themselves are actually quite clean. When I first received the lens, the aperture scale and index mark did not line up correctly. I spent quite a bit of time disassembling the entire optical block and aperture ring, then recalibrated and reassembled it so that each aperture marking now aligns perfectly with the indicator.

The most distinctive characteristic of this lens is its rendering wide open: contrast is very low and the image appears soft and dreamy, but once stopped down, the contrast improves significantly. In the first photo, the background blur behind the uBike bicycle seems to “melt away” into the distance, while the highlights carry a slightly creamy texture with a hint of swirl, producing an exceptionally smooth bokeh.

我收藏的第三顆蘇聯鏡頭是Jupiter-9 85mm f2 MC，與戰前的CONTAC RF相機接環的Carl Zeiss Jena Sonnar 85mm f2有著濃濃的血緣關係。這顆鏡頭是上個世紀80年代後期製造的，有冠上MC鍍膜，雖然外觀磨損的很厲害，鏡片倒是蠻乾淨的。這顆鏡頭剛到手時，光圈環的數字和指標位置有些差異，我費了一些功夫拆下整個鏡組和光圈環，將光圈環重新鎖定在正確的位置，讓每個光圈環的數字和指標都能對得上。

這鏡頭最大的特色是在光圈全開時，反差很低、很柔和，但縮光圈後反差也就好很多。第一張照片uBike腳踏車背後，散景一路往後「化開」，高光邊緣帶一點奶油感與旋轉感，非常滑順。

Industar-61-L/Z MC 50mm f2.8 and Sony A7C

2026/3/22





My very first Soviet lens collection piece, the Industar-61 L/Z MC 50mm f/2.8, is back in action. I took it for a walk around the National Taiwan University campus to soak up some sunshine. Under bright sunlight, using the sparkling highlights filtering through the leaves as the background, this lens can produce its signature “star-shaped bokeh” effect.

Over the past few years, NTU has been undergoing constant redevelopment. Old buildings have been demolished one after another, while new buildings funded by alumni donations continue to rise. Even NTU Xiao-Fu, where I used to bring my kids on weekends, has been torn down. Over these past two decades, my photos of the NTU campus have gradually evolved from Fujifilm slide film and peel-apart film to digital photography and Instax film.

我收藏的第一顆蘇聯鏡頭 Industar-61-L/Z MC 50mm f2.8 又出動了，帶它來台灣大學校園走走，曬曬太陽。在大太陽下，以樹葉的點狀反光作為背景，就可拍出這顆鏡頭特有的「星狀散景」效果。

這幾年台大持續大興土木，老舊建築一棟一棟的拆，校友捐贈的新大樓一棟一棟的蓋，以前週末溜小孩的台大小福也拆掉了。這二十幾年來，我拍台大校景的照片也從富士正片、撕拉片，漸漸得變成數位相片、Instax底片。不變的就是手上的四十幾棵手動對焦老鏡頭，拜各種轉接環之賜，得以在數位相機和拍立得相機上復活，使得一些傳統優質老鏡的價格也水漲船高。


Industar-61-L/Z MC 50mm f2.8


Industar-61-L/Z MC 50mm f2.8


Star-shaped bokeh, Industar-61-L/Z MC 50mm f2.8


Industar-61-L/Z MC 50mm f2.8

Pentax SP1000 + SMC Takumar 55mm f1.8 + AGFA vista+ 400 film Test (expired 10 yrs.) 過期10年底片測試

2025/3/22

Today I'm sharing the Pentax SP1000, which is very common in the M42 camera world. The version most commonly seen in Taiwan bears the Asahi Optical (旭光學 Asahi) branding, but this particular camera was exported to the U.S. and carries the Honeywell branding instead. The standard lens I paired with this camera is a later version of the SMC Pentax Takumar 55mm f1.8. Its image quality is above average, though personally, I find the Auto Chinon 55mm f1.7 MC to be slightly superior in comparison. Below are a few test photos taken with this setup. The film used was AGFA Vista Plus 400, which had been refrigerated and expired for 9 years and 4 months.

今天分享的是在M42相機領域很常見的 Pentax SP1000， 在台灣常見的版本是有旭光學 Asahi 標誌的相機，而這台相機卻是外銷美國，打上美國品牌 Honeywell 標誌的版本。我搭配在這台相機上的標準鏡頭是後期的 SMC Pentax Takumar 55mm f1.8，成像品質算是中上，個人覺得與 Auto Chnon 55mm f1.7 MC 相比，後者還是比較優，以下是幾張測試照片，底片是冷藏保存過期9年4個月的 AGFA vista plus 400。

Zenit 12XP + Helio-44m-5 58mm f2 MC + AGFA vista+ 400 film Test (expired 10 yrs.) 過期10年底片測試

2025/3/22

The Zenit 12XP from the Soviet era found its way into my collection mainly because it came bundled with the Helios-44M-5 58mm f2 MC lens. I think most enthusiasts familiar with the history of M42 cameras probably know that the Helios-44 series is derived from the Carl Zeiss Jena Biotar lens. Under certain apertures and backgrounds, it can produce a unique swirling bokeh effect. Unfortunately, due to the limited number of shots I had with this roll of film, I wasn't able to achieve that effect this time.

蘇聯時期的 Zenit 12XP 會出現在我的收藏中，其實是跟著 Helio-44m-5 58mm f2 MC 這顆鏡頭一起來的。我想大部分知道M42相機歷史的同好，應該都知道 Helio-44 這一系列的鏡頭是源自 Carl Zeiss Jena Biotar 鏡頭，在特定的光圈與背景下可以拍出背景旋轉的特殊效果。很可惜在這次有限的底片張數測試下，我沒有成功。

Back to the Zenit 12XP itself — compared to Japanese SLRs, its body is narrower but taller. The shutter advance feels quite snappy, and after using it, switching back to a Japanese camera makes the film advance feel surprisingly heavy. Judging from this roll, the Helios-44M-5 58mm f2 delivers very sharp image quality. Below are a few test shots. The film used was AGFA Vista Plus 400, which had been refrigerated and expired for 9 years and 4 months.

回到 Zenit 12XP 這台相機，相較於日本血統的單眼相機，它的機身較窄但高度較高，快門過片算是輕快，剛操作完轉回日本相機時，會覺得日本相機過片還真是費力。從這次拍攝的底片來看，Helio-44m-5 58mm f2 的成像相當銳利。以下是幾張測試照片，底片是冷藏保存過期9年4個月的 AGFA vista plus 400。

Chinon CM-3 + Auto Chinon 55mm f1.7 + AGFA vista+ 400 film Test (expired 10 yrs.) 過期10年底片測試

2025/3/22

Since I started getting into photography, I had always thought CHINON only made point-and-shoot cameras. It wasn't until I discovered the CHINON CM-3 SLR that my impression changed — it turns out CHINON was actually a very capable camera manufacturer. The way I came across the CHINON CM-3 was quite special. M42 mount cameras trace back to the 1945 CONTAX S, and brands like Pentax, Fujica, and Yashica continued producing M42 cameras using cloth shutter curtains. Unfortunately, this material tends to degrade over time, and many Pentax M42 cameras suffer from this issue today. Because of that, I started looking for M42 cameras with metal shutter curtains. The Voigtländer Bessaflex TM, produced by Cosina after 2000, would have been the top choice — but sadly, I had just sold my long-held one at a high price. Eventually, while browsing through various M42 camera listings, I came across the CHINON CM-3, one of the rare M42 cameras to use a vertically traveling metal shutter. Its appearance is strikingly similar to the Nikon FM/FE series from the same era. I couldn’t help but wonder — how did I never know CHINON also made such solid SLRs? Truly, I was unaware and underinformed.

從我開始玩攝影以來，我一直以為CHINON只有生產傻瓜相機，直到發現這一台CM-3單眼相機才讓我改觀，其實它也是一家實力雄厚的相機公司。而發現這台CHINON CM-3也是很別，由於M42接環的相機源自於1945年的CONTAX S，後續各廠牌如Pentax、Fujica、Yashica等M42相機一直以來都採用布質的簾幕快門，這樣的材質年代久了之後容易老化，許多Pentax M42相機就有這樣的問題。基於上述原因，我開始找尋具金屬簾幕快門的M42相機， Cosina在2000年後生產的 Voigtländer Bessaflex TM 應該是首選，無奈我才剛高價賣掉一部多年的收藏。最後從許多M42相機的拍賣文中發現了CHINON CM-3是一台少數採用金屬縱向簾幕的M42相機，而且外觀與同期的Nikon FM/FE系列相機神似，唉，我以前怎麼不知道CHINON也有這麼扎實的單眼相機呢，真是孤陋寡聞啊。

The CHINON CM-3 came with the Auto Chinon 55mm f1.7 MC lens, which is widely believed online to have been made by the famous Tomioka Optical factory. In actual use, the image quality is excellent. Below are a few test shots. The film used was AGFA Vista Plus 400, which had been refrigerated and expired for 9 years and 4 months.

CHINON CM-3搭配的鏡頭是 Auto Chinon 55mm f1.7 MC，網路上普遍的說法是來自有名的富岡光學代工廠，實際拍攝起來成像品質極佳，以下是幾張測試照片，底片是冷藏保存過期9年4個月的 AGFA vista plus 400。

Auto CHINON MC 55mm f1.7 M42 on Sony A7III

2024/6/9

Today, I took my CHINON 55mm f1.7 lens, which I've been collecting for years, out for the first time to shoot some flowers and plants. After attaching a 12mm extension tube and an adapter, I mounted it directly onto my Sony A7III digital camera. This setup basically turns it into a macro lens with a magnification of around 1:4 to 1:2.5. If I switch to APS-C mode, the magnification goes up to about 1:1.5, making it easy to capture close-up shots of the little yellow daisies (Wedelia) like the one shown here.

今天第一次帶著收藏多年的CHINON 55mm f1.7出門拍些花花草草，裝上12mm的延伸環和轉接環後直上Sony A7III數位相機，基本上就是約1:4~1:2.5的微距鏡頭了，如果再切換到APS-C模式，就是1:1.5左右的倍率，很容易就可以拍出以下小黃菊(蟛蜞菊, Wedelia)的近拍照。


Auto CHINON MC 55mm f1.7 + 12mm extension tube

I hadn't paid much attention to this lens before, mainly because I bought it along with the CHINON CM-3, an M42 film camera. Since CHINON was primarily an OEM for cameras and lenses, and its own brand was often associated with budget cameras and lenses, I didn’t particularly care about the optical quality of this lens. However, after recently researching this 55mm f1.7 lens online, I came across a claim that it was manufactured by the renowned Tomioka Optical. This piqued my interest, and I decided to give it a try.

以前沒有特別注意這顆鏡頭，主要是因為它是跟CHINON CM-3這台M42底片相機一起購入，由於CHINON本身是相機和鏡頭代工廠，自主品牌則常是廉價相機鏡頭的代表，我對這棵鏡頭的光學品質並未特別在意。前這子網路上查詢這顆鏡頭的資訊時，看到一種說法，即這顆55mm f1.7的鏡頭是有名的富岡光學代工，也就興起了試拍的念頭。


Auto CHINON MC 55mm f1.7 M42

In June, before the peak of the hot summer, the pathway along the Sunshine Bridge in Xindian is lined with blooming little yellow daisies. The insects are also drawn to the flowers, lingering and flitting back and forth.

六月天，在進入炎熱的夏季前，新店陽光橋下的步道沿線都是盛開的小黃菊，蟲兒也受到了吸引，流連往返。

Auto CHINON MC 55mm f1.7 + 12mm extension tube


Auto CHINON MC 55mm f1.7 + 12mm extension tube


Auto CHINON MC 55mm f1.7


Auto CHINON MC 55mm f1.7