I Love my 400/4 DO lens and over the years wonderful images were captured with it, until.......
recently there was something loose inside. It was the AF distance scale which is normally visible through the clear window as the AF is rotating.
I found out that Canon USA does not support this lens any more.
Desperately, I thought to fix it by myself. I was hoping that this loose part can be pulled out through the control switches opening. The four screws were carefully removed exposing the loose scale which is a plastic part.
To my surprise this part is not secured to the AF internal real with nothing other than contact glue.
Over the years the glue was drying out causing the scale to become loose, wondering around in the internal cavity.
What a shame.
It is a bit tricky to pull the curved plastic out, but it is doable.
If anybody encounters the same problem I am willing to provide more info.
The bottom line is:
My beloved 400/4 DO is now convertible.
I have found an "L" lens which has an internal part glued.
I am wondering if this is the practice used in other "L" lenses, and I own quite few of them.
In case same thing happens to another "L" lens, it shall not be as forgiving as the 400/4 especially if Canon is not willing to re-glue the AF scale.
I Love my 400/4 DO lens and over the years wonderful images were captured with it, until.......
recently there was something loose inside. It was the AF distance scale which is normally visible through the clear window as the AF is rotating.
I found out that Canon USA does not support this lens any more.
Desperately, I thought to fix it by myself. I was hoping that this loose part can be pulled out through the control switches opening. The four screws were carefully removed exposing the loose scale which is a plastic part.
To my surprise this part is not secured to the AF internal real with nothing other than contact glue.
Over the years the glue was drying out causing the scale to become loose, wondering around in the internal cavity.
What a shame.
It is a bit tricky to pull the curved plastic out, but it is doable.
If anybody encounters the same problem I am willing to provide more info.
The bottom line is:
I have found an "L" lens which has an internal part glued.
I am wondering if this is the practice used in other "L" lenses, and I own quite few of them.
In case same thing happens to another "L" lens, it shall not be as forgiving as the 400/4 especially if Canon is not willing to re-glue the AF scale.
Nov 20, 2025 at 12:50 PM
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