Lens problem: Aperture won't close - anybody ever had a similar problem?

[Markus Jais]

Hello,
this morning I was photographing flowers with my EF 4/300L IS. The first shots were taken with f4 and everything was fine.
Then I stopped down to f8 and the image was terribly overexposed. But the EOS 7D was set to f8 (using AV - aperture priority)
and the camera correctly chose a longer shutter speed.
I then pushed the depth of field preview button and heard the noise I always hear when I press the button and the aperture closes but
no matter which f-stop the image in the viewfinder didn't get any darker.

It must be a problem with the lens because I also checked my 4/70-200L IS and 3.5/180L and they both worked fine.

A few days ago I did AF micro adjustments for the 4/300L IS but I doubt that this has anything do to with the aperture not closing. And it works fine with the 4/70-200L IS where I also did AF micro adjustments.

Has anybody ever had a similar problem? I will probably have to send the lens to Canon but wanted to ask first. I've never experienced anything like this before with any lens.

Any advice or similar experience would be very interesting.

Markus

[arash_hazeghi]

try cleaning the lens contacts with alcohol and lens cloth.

[Markus Jais]

Hi Arash,

thanks, I tried that but it didn't work. I also tried it on my old EOS 40D and with a 1.4x and always the same. I fear the lens is broken. I never dropped it or used in harsh
environments like a rain forest. But things break. I will probably send it to Canon for repair. I hope that won't cost much.

Markus

[Don Lacy]

Send it to Canon to get fixed the aperture is stuck at wide open it happens.

[Markus Jais]

Gave it to my dealer who will send it to Canon. I expect to pay at least 200 Euros for this (which I would rather spend on a 5d III), maybe even more. This sucks but sometimes things just break.

Markus

[Don Lacy]

How old is the lens

[Markus Jais]

The lens is about 5 years old.

Markus

[Don Lacy]

The lens is about 5 years old.

Markus

If it was closer to the warranty it does not hurt to ask Canon to fix free of charge or at a discount but I doubt they will do it for a 5 year old lens. Canon replaced a shutter once for me on a camera that was 4 months out of warranty free of charge.