I have owned a Canon 300 f4 L IS for about a year without much use until now. I use is with a 35 mm camera, 30v. I have just noticed that all shots with this lens have a slight overexposure along the bottom of the frame in a wedge shape being larger in the right hand corner. Has anyone had this experience? What could cause this? It happens with and without a 1.4 extender and with all film types.

I would say look at the foam seals in the back of your camera. Sounds like a light leak onto the film. It is not too expensive to replace the foam.
Another possibility is that the shutter is hanging up. The camera may be due for a good cleaning and tuneup.


Rich

As I do not have the problem with my other lens including a 70-300 DO IS I assume it must be the lens and not the camera.

Then I would say you have made a correct assumption.
Perhaps it is time to send the lens to Canon for repair.

Rich

Thanks Rich,

Your first response has got me thinking. I have been using this lens at max aperture and ISO400 film giving shutter speeds above 1000. It maybe that the shutter is faulty at the higher speeds.

Regards
Martin
NSW Australia