FDn to EF Mod (without Glass) Easy Steps




Introduction: FDn to EF Mod (without Glass) Easy Steps

Welcome to this Tutorial.

This tutorial shows how to modify a FDn Lens to use it with actual EF EOS DSLR Cameras. FDn lenses have a great quality but they can be used on EOS DSLR without an adapter, that contain a corrector glass that allows an FDn Lens to reach infinity focus.

With a Mount modification is possible to reach infinity focus without a corrector glass, without damaging the lens.

You can follow the steps or watch the video:


Step 1: Materials

For the modification you will need:

  1. Crosstype PH0 screwdriver.

You can follow the links bellow to obtain each piece, acording to the modification you need.

  1. FDn to EF mount
  2. Aperture Arm Option A 3mm or Aperture Arm Option A 10mm
  3. Aperture Arm Option B 3mm or Aperture Arm Option B 10mm

Step 2: Preparing the Lens

After all, set your aperture into A.

  1. Turn the aperture ring until 22.
  2. Press and hold the button of the aperture ring.
  3. Turn anticlockwise the aperture ring to secure the ring to A mode.

Step 3: Disassemble the FDn Mount

  1. Locate the 3 crosstype screws around the mount. This screws hold the silver mount flange
  2. Remove the 3 crosstype screws around the mount.

Step 4: Remove the Rest of the Mount

  1. Remove the silver ring using your screwdriver or a stick. Be carefull to NOT damage the rear element.
  2. Turn anticlockwise the internal aperture mechanism until you hear a click.
  3. Remove the internal aperture mechanism.

Step 5: Diassemble the Mount

  1. Locate the 3 crosstype screws, 2 black screws and one silver.
  2. Remember the location of the screws before you remove them.

Step 6: Optional Step - Removing the Aperture Control Ring

If you have the first model of the new aperture control, follow this steps.

  1. Unlock the aperture ring from A mode to f/8.0.
  2. Look that the little gap of the aluminum control ring match the flange of the black plastic aperture ring.
  3. Remove the aluminum ring by raising it.

Step 7: Selecting the Aperture Arm

You can use one of both aperture arms, depending on the FDn lens you want to modify One may be better than the other for some lenses.

Identify the two silver posts that control the aperture and the trapezoidal bump located in the black plastic aperture ring.


  1. Locate the new aperture control arm between the two posts and the bump of the aperture ring.

B. (Follow this step if you have NOT removed the aluminum aperture control ring)

  1. Locate the new aperture control arm between the two posts and the pin of the aluminum ring

Step 8: Mount the FDn to EF Mount

  1. locate the FDn to EF mount.
  2. locate the 3 screws you removed before in their correct place.
  3. Done!.

You finish the modification, you can use your FDn lens with your EF DSLR with a great quality glass.

Before start playing with your new lens, read the following recomendations please.

Step 9: Recomendations

As the flange distance of the FD SLR cameras where 42mm and the new EF DSLR cameras is 44mm, the glass may be go 2mm extra milimeters inside, for Full frames cameras like Canon 5D mkII, III or IV and Canon 6D, it is a problem as the mirror may collide with the rear optic of the lens.


Avoid taking a picture focusing infinity with and modded FDn lens.

Avoid focus infinity and then turn off your camera, as the mirror can get stuck with the rear elements of the FDn lens.

Avoid taking a picture while you are recording video, to avoid collision.


The correct way to use a FDn lens to record video or take a picture is:

  1. Locate your camera in your lens before turning it on.
  2. Focus to the closest focus distance. (45cm or 50cm)
  3. Then turn on your camera in video mode.
  4. Enjoy.

Follow the steps backwards to remove your FDn lens correctly.

Thanks for your time. Share and Suscribe to my youtube channel.

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    2 Discussions


    Question 2 years ago on Step 1

    Hey which two arms are specifically needed for the Canon 50mm 1.4 lens? I want to order the parts but Im not sure which ones I need.
    Thanks in advance

    Pedro C
    Pedro C

    3 years ago

    Sorry about the links, I have updated them!!!