Repairing a Canon Lens (50mm f1.8)

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Taking the initiative to repair your own camera lens can be both cost-effective and quick. You can literally save hundreds by performing do-it-yourself on your gear, and you can have an immediate fix instead of waiting days or weeks - and paying out the wazoo - for a shop to fix it. On the other hand, it can be time-consuming if this is your first time doing things yourself. If you are not one who finds enjoyment in puzzles, this might not be for you.

That being said, I have a


Please, please, please, take my advice on this!

Any piece of photographic equipment, including a lens, is a product of extensive and highly sophisticated engineering, and as such they carry a hefty price tag. They also come with a very important feature: a warranty. Unless you are a professional camera technician, please do not take it upon yourself to disassemble a lens that will be fixed free of cost by the manufacturer. Once you fully read this tutorial, be prepared to throw your lens away if you do not completely understand all the steps and feel confident performing them!

Repairing a Canon 50mm f1.8 II Lens

This lens is not the USM version, and there are different construction features between them. It is the Canon 50mm f1.8 II Lens.

Tools you will need
* #00 Philips head screwdriver - this fits all screws on the lens.
* #00 Flat head screwdriver, or something similar - you will need a small tool for removing the inner lens mount.
* Cleaning agent (i.e., methanol) - don’t leave any fingerprints on your glass!
* Along with this, use rubber gloves if you feel cleanliness is that important. Recommended, but not required.
* Silicone lubricant (when reassembling)

Getting Started

1. Turn your lens so that the lens mount is facing up. There are two screws that hold the electrical contact board in place. Remove these.

2. Once the screws are out, use your screwdriver to push the board into the cavity below, until you can put it under the edge of the plastic insert. Don’t worry, there’s room. Take care not to touch or scratch the electrical contacts.

3. Gently (and I mean gently) reach under the edge of this plastic insert and push the tab as shown toward the center until it pops loose. Be careful not to bend this too far or you risk breaking it.

4. Once you lift the tabs, you can remove the insert and set it aside.

5. This is a top view (well, bottom really) of your lens. This circuit board makes up the lens portion of Canon’s EOS circuitry, regulates aperture control, and sends data to and from the camera body for auto/manual focus information.

6. The AF/MF switch located on the lens barrel is connected to the internals by a very small metal arm which is very fragile. Take care in removing this. The switch is on a plate approximately 1”×2” around the barrel, and can be removed by using a blade inside the red alignment marker. Read the next step before performing this one.

7. You will find that it is held in place by an adhesive strip. Once you separate this, you will need to find a different way to secure the plate when reassembling your lens. In my experience, there is enough residual “stickiness” to keep it in place, but don’t rely on it.

8. Once all this is done, you are ready to remove the inner barrel. There is an interlock that prevents removal of this barrel unless the focusing ring is rotated to its full clockwise position (as viewed from the front of the lens). This will move the front of the lens fully toward the rear lens mount. Pull on the focusing ring (you may have to push from the other end) and remove the inner barrel carefully. Keep in mind that the electrical contact board is hanging loose, so take care not to tear it or pull it off the circuit board.

That’s as far as this tutorial goes for now, folks. From here you can attack most mechanical problems. One note: if you are removing the circuit board, you will need to be proficient in soldering and de-soldering techniques, as you will have to physically de-solder the focusing motor from the board.

For reassembly, perform the above steps in reverse. Please remember to exercise extreme caution when repairing your lens!