Recently I had the misfortune of Jamming the fixed lens hood on my beloved Canon 400mm f5.6. This meant that the built in hood is unable to be retracted making it impractical for storage.
I contacted Canon for advice and they stated that the lens would need to be sent in for repair and quoted an obscene amount of money to complete the job. This seemed to be quite unfair as optically and mechanically the lens was fine. So I thought that I would see if it possible to repair the lens myself. As it turns out it a really easy job that will save you a ton of money.
Below I will detail step by step guide to getting you through the job.
1- Remove the rubber ring from the top of the lens. this just pulls off.
2- Under the ring you will see some small notches. These allow in inner metal ring to be unscrewed. I tried to use regular screwdrivers to do this but found it was fixed on too tight. I found that a special lens tool was cheaply available on Amazon and ebay. With this tool the metal ring was easily unscrewed.make sure the lens cap is in place to protect the front element.
3- With the metal ring removed the lens hood is now able to slide back off the lens body. You will now find the cause of the problem, which will be a perished rubber band. This is technically known as a hood stopper and will cost you around £12. I was able to source one HERE but if you cant the correct part number is CA2-0395-000.
4- When I installed the new hood stopper which simply slides on over the body, I also added a little glue to the recess it sits in for added strength and security.
No all that's needed is just to reverse the steps to reassemble the lens.
In the unlikely event of any damage. The above is undertaken entirely at your own risk.