Annoying 300mm 2.8L USM Problem . Any help ?

Hello all .

I have , I belive an early 90s Canon 300mm 2.8L lens . It is obviously pre IS . Apart from this problem it is all in good condition .

Basically this is the easiest way to describe the problem.

When shooting a sequence of between 3-6 photos (Burst shooting ,1 after another) , the middle image and more frequently the last image will be randomly brighter and slightly out of focus . I presume this is a problem with my lens , as I have tested it on both of my 1d Mk2 N bodies and it does the same on both bodies .

Have any of you had this problem , and has anyone had one of these older lenses repaired recently ? Im worried that it is too old to be repaired .

Thanks Jamie

aperture problem?

are you shooting in AI SERVO?

Yes I am .

I don't have that particular lens and haven't had that problem with any of the lenses I do have...

But it sounds like a sluggish lens aperture. It might need parts replaced or just a good cleaning. Hard to say.

You might try cleaning the lens-to-camera electronic contacts. Just use a few drops of isopropyl (rubbing) alcohol to dampen a clean cloth and carefully wipe the contacts with that... both on the lens and the corresponding pins in the camera. Be careful to keep off the lens optics and the camera's mirror. That's really all you can do yourself.

If that doesn't work, get someone to look at it and give you a quote. It's not going to get better on its own or be something you can fix yourself.

Spoke to a Canon repair centre today and they are unable to repair my lens . Anyone have any idea of where , if anywhere that would be able to help ?

Canon no longer support this lens for repairs, but it may not be broken. Check if they can service it, if the aperture is a bit gummed up I would have thought they could sort that out and if parts are needed they could tell you which ones - might be worth a phone call?
There are still spares out there so it is well worth looking.

What aperture are you shooting at? I'd guess that if you were shooting stopped down a little, f/4 maybe, then the blades are sticking and you are actually shooting at f/2.8 or something for the brighter shots.

Try looking into the lens and pressing the DOF preview button rapidly. You might be able to see the blades stick.

It seems to do it at any aperture . By the sounds of it , it does sound like the blades are sticking .I will try and get hold of someone to see if they can service it .

-jamie- wrote in post #15197849
It seems to do it at any aperture . By the sounds of it , it does sound like the blades are sticking .I will try and get hold of someone to see if they can service it .

Is it doing it at f/2.8 ?

If so, then it probably isn't a sticking aperture mechanism as the aperture blades don't close down at all when shooting wide open.

Have you tried stopping down whilst looking through the lens from the front? You should be able to see the blade action by stopping down manually (use the depth of field preview button) whilst looking through the front end. Make sure the viewfinder is pointed towards a nice bright area, a white wall for instance, to give you a clear idea.