Disassembly steps for cleaning front and back lens elements

CANON FD  50MM 1.8 Lens

CLEANING MATERIALS

1. REMOVE FRONT NAMEPLATE

Use a plastic wedging tool to lift the filter plate. Be careful not to scratch the front element. 

2. CLEAN NAMEPLATE

The front filter nameplate is plastic. Put this under running water to clean any gunk off it.

3. REMOVE 3 SCREWS

The 3 screws hold the front filter and secures the front lens group.

4. CLEAN FILTER RING

Clean the filter ring under running water

5. REMOVE FRONT LENS GROUP

Slowly tip the lens over and the front lens group will slide out

6. REMOVE RETAINING CLIP

Use a thin stiff blade to remove the plastic clip

7. TAKE A BREAK

The front lens group should like this and is ready to be separated

8. SEPARATE  LENS GROUP

Use a suction device to separate

9. CLEAN LENS

Use a Qtip and clean the back of the front element with lens solution. 91% isopropyl alcohol is mild enough on these lens coatings.

10. CLEAN  FOCUS RING

Use a Qtip and work around the inside of the focus ring

11. INSPECT APERTURE BLADES

Mount an adapter to allow adjusting the aperture. If blades show any signs of oil, clean them with a qtip. Be very gentle!

12. INSPECT REAR LENS GROUP

Open the aperture all the way and inspect the rear group. Clean the lens that exposed behind the aperture if required

13. REASSEMBLE FRONT GROUP

Reverse the steps to reassemble the front lens group. You can disassemble further if you want to clean the helicoid, but do this at your own risk.

14. REMOVE 3 MOUNT SCREWS

Flip the lens and remove the 3 screws holding the mount to the lens

15. REMOVE MOUNT

Attach the adapter to the lens and rotate to lock into position. Pull-on lens adapter to separate metal lens mount with the lens

16. CLEAN  MOUNT PLATE

Removing the metal mount and the lens should appear as above. Clean the gunk

17. CLEAN METAL PLATE

Leave the metal mount on the adapter. Use a qtip to clean it

18. CLEAN AREA AROUND LENS

Clean the area around the rear lens group

19. REMOVE RETAINING CLIP

Use a stiff blade to remove the retaining clip holding the rear lens elements.  Wedge in and lift, don't use to much force.

20. CLEAN RETAINING CLIP

This is how the clip looks if you haven't destroyed it.

21. CLEAN REAR ELEMENT

Carefully flip the lens and the rear element should drop out. The curved side is the one that should be facing the outside of the lens.

22. CLEAN INSIDE REAR ELEMENT

This element can also be removed for cleaning but you can just leave it in current position and clean from here

23. EXAMINE REAR PLATE

Examing the rear plate so you are familiar with how to line up the levers. This is the hardest part of reassembly.

24. POSITION LEVERS

The levers need to be in this position for the mount to reattached. Pay attention to the highlighted area. Use a flat screwdriver to move the black circle so levers can be moved into position

25. POSITION LEVERS 2

Use a paper clip to push the level and hold it into position. You can also just use your fingers.

26. LINE UP LEVERS

The highlighted part need to be mated together

27. LINE UP LEVERS 2

The highlighted part needs to be mated together

28. ATTACH MOUNT PLATE

If you have lined things up correctly, it should sit flush and look like the above

29. ATTACH  METAL MOUNT

Line up the 3 holes with the metal mount. Push the mount down until all 3 are aligned. Fasten screws

LENS CLEANING DONE

If you don't have the tools you can buy them here.