Tag: Lens

Disassembling the Asahi Takumar 135mm f3.5 (Pre-set v.1) Lens

I picked up a near-mint vintage Asahi (Pentax) 135mm f/3.5 version 1 lens from Lucky Home (LH) Cameras, tucked away in the Miami Bayside Bangpu area of Bangkok. The place is a treasure trove of old and vintage Japanese cameras and lenses—though the pricing seems to depend entirely on the day you visit. When I dropped by on a Thursday, they were advertising a 70% discount across the board. Whether that’s a genuine deal or just a clever marketing ploy, I couldn’t resist. The lens was in beautiful condition, and at that price, it felt like a steal.

I snagged this Takumar lens for just 600 Thai Baht after the discount—roughly USD 18. A total steal, if you ask me. For a 65-year-old piece of glass, it was in surprisingly good shape: nearly mint, with only a hint of fungus and a slightly stiff focus ring. I scoured the internet hoping to find a disassembly guide, but came up empty-handed.

The build quality is impressive—classic Takumar craftsmanship. No visible screws anywhere on the barrel, save for three tucked away at the rear mount. It’s the kind of lens that feels like it was engineered to last generations.

Removing the front elements is straightforward—just unscrew the entire front element group.

Next, detach the rear lens mount assembly by unscrewing the three visible screws located around the rear section. Once removed, the entire mount should lift off cleanly, giving you access to the internal components.

To remove the front pre-set aperture assembly, you’ll need to unscrew the two helicoid guide pins now visible from the rear. These guides secure the focusing mechanism and must be taken out to allow the aperture assembly to rotate out free. I chose not to remove the rear lens elements, as they were already clean and in excellent condition.

Before removing the helicoid guides, I carefully marked their positions to preserve infinity focus. I rotated the focus ring to the infinity setting, then scratched two faint reference lines where the tops of the guides aligned. These marks will serve as crucial alignment cues during reassembly, helping ensure the lens maintains proper focus calibration.

When removing the helicoid guides, make sure to note which guide fits into which groove. Each guide is slightly different, though the reason behind this design choice isn’t immediately clear. It might have been for fine-tuning focus alignment or simply a quirk of the manufacturing process. Either way, keeping track of their original positions is essential for smooth reassembly and accurate focusing.

Finally, the aperture housing can be separated from the focusing mechanism. However, before you disengage the helicoids, it’s absolutely critical to mark the exact point of separation. A small scratch or reference line will ensure you maintain the correct orientation during reassembly. Without this, you risk misaligning the helicoids—since they can thread together in multiple configurations, but only one will restore proper focus calibration. Skip this step, and you’re in for a frustrating reassembly process.

Next, you can remove the distance scale ring. It’s secured by five screws positioned on the inner side of the ring. Pay special attention to the middle screw—it’s longer than the others and also functions as the mechanical stop for infinity focus. Before removing it, make sure to note its exact position when the distance scale is set to infinity. This reference will be crucial for restoring accurate focus during reassembly.

Once the distance scale ring is removed, the orientation of the screws becomes clearly visible. At this stage, you’ll also notice a sixth screw—the near-focus stop screw—revealed after the focusing ring is taken off. It’s important to carefully note its position relative to the infinity stop screw, as both play a crucial role in defining the lens’s focusing range. Marking or photographing their alignment before disassembly can save a lot of guesswork during reassembly and help maintain accurate focus calibration.

Remove the near focusing stop screw and the brass helicoid ring can be rotated out.

After thoroughly cleaning and relubricating the helicoids, reassembly was smooth and uneventful. Everything clicked back into place with satisfying precision—no surprises, no fuss.

Thanks for reading, and I hope this walkthrough helps fellow vintage lens enthusiasts breathe new life into their classic gear!

Why I Like Lenses from the 70’s and 80’s

Recently I acquired a Nikon SLR with an AF-S DX Nikkor 35mm f1.8 G lens attached to it. While I was not planning to get the lens, I thought this was a bonus.

This particular Nikon lens was released in Feb 2009 primarily for Nikon’s DX range of DSLRs (digital SLRs). The lens was primarily targeted as an inexpensive, large aperture option for users of the entry-level (D40 / D40X /D60) series of DSLRs. It is small, light and cheap and had relatively good reviews. It had the silent-wave auto-focusing system, meaning that the autofocus mechanism was in the lens and not the body, theoretically making it faster to autofocus.

When my lens arrived, it looked in good condition. The glass was clear, the focusing ring was smooth. However, when I attached it to the camera, it could not focus fast enough. It kept hunting for focus. I thought it was the camera body, so I changed the body. Same issue. Cleaned the electronic contracts, tried it outdoors in bright light and larger apertures, no difference. The lens still hunted for focus.

Eventually I looked to the internet to see if anyone else had similar problems. There were a couple of posts mentioning focus hunting issues with this model of 35mm lens. One poster, disassembled his lens and cleaned the gears of the silent-wave mechanism. Apparently that got rid of the problem. I decided to do the same.

Starting with the rear of the lens, I unscrewed the 4 small screws securing the mounting ring.

Next 3 screws to come off were the ones holding the black plastic part of the lens mount in place.

Before the metal lens mount ring could be detached, the lens contact points had to be released from the mount. This was held in place by 2 small screws. The lens contact points are connected to the lens CPU by a cable, hence the contact points have to be detached before I could remove the lens mount ring completely.

Care should be taken when removing the lens mount ring from the barrel, as there are several rings of different thickness below the main ring that can fall off if you remove the mount quickly. All these rings are held together by an outer rubber ring which also comes off when the mount is removed. This is the first of many inferior aspects of this G lens construction that I noticed. Nikon lenses of higher quality do not have all these rings and there is no rubber holding rings together. In the higher quality Nikon lenses, the lens mount is one solid block of metal.

Once the lens mount ring and all the other rings are removed, the next step is to unscrew the single screw holding the focus selector switch in place. After this screw is removed, the lens barrel cover can be slowly slid out to reveal the inside of the lens. However, the focus selector is connected by wires to the CPU, hence, the lens barrel needs to be removed slowly leaving the focus selector dangling by the wires still connected to the main barrel.

Once the inside of the lens is revealed, you can see the silent-wave motor and focusing mechanism (top left picture), the contact points for correct autofocusing of the lens (top right picture), cables to the lens CPU (bottom left picture) and the lens CPU (bottom right picture). All these are held together on a plastic barrel frame. There is hardly any metal in the barrel. The use of brittle plastic for the barrel frame is another inferior construction feature to keep the cost of this lens low. Even the lens elements are held in plastic frames.

To access the silent-wave motor next, the focusing ring needs to be removed. In the pictures above, the lens is held by the focusing ring.

Turning the lens around, the first step is to remove the cover ring to expose the screws holding the focusing ring in place. Initially I was confused as to how to remove it as there is only one notch on the cover ring. Usually there are 2 notches directly opposite each other so that you can use lens ring wrenches to unscrew them. For this cheaper construction this cover ring is held by double-sided tape! All I had to do was to slowly pry it off with a small screw-driver.

There are 2 sets of 3 screws that can be seen once the cover ring is removed. Not sure which ones hold the focusing ring in place, I proceeded to unscrew the metallic screws. Wrong ones! Those hold the plastic frame that houses the front lens element. This is a first time I have seen lens elements housed in plastic frames! Another cost cutting construction by Nikon.

Removing the black screws finally released the focusing ring, which has plastic gear teeth that locks into the focusing gear (plastic as well) of the barrel.

With the motor mechanism exposed, I cleaned the motors and gears with 90% alcohol. After which I reassembled the lens mount but not the barrel cover to check if the lens focussing issues were resolved. Unfortunately, the lens performed no better.

Puzzled, I examined the barrel closer with my loupe. Sad to say, I noticed a crack in the plastic gear that moves the brass auto-focusing contacts. In fact the crack was more extensive, extending diagonally from the base of the focusing ring to the base of the lens mount. What!

The crack completely separates the ring that forms the plastic gear for the auto-focusing contacts. This was obviously the problem.

This lens must have suffered a knock previously and while the damage was not obvious externally, it caused a long diagonal crack in the internal all plastic frame of the lens barrel.

This will never happen in a lens constructed in the 70’s or 80’s, which have far superior metal construction. While the AF-S DX Nikkor 35mm f1.8 G lens looks nice, I wouldn’t recommend it for its cheap all plastic construction. An accidental knock on a wall, or a knock on a lamp post or a drop from the camera bag to a concrete floor will likely render the lens non-functional!

I am sticking to pro-level lenses or old metal lenses even if they don’t have fancy autofocus. The Nikkor of years gone by were quality “glass in metal”!