I have a Canon EOS 400D with a EFS 17-85 mm lens. The camera doesn't capture a picture with this lens attached. It focusses back and forth exactly once per click. I tried with different modes and its the same. When set to auto, the camera correctly auto adjusts the settings like exposure time, but its not changing the F stops. Looking through the viewfinder also shows a dark preview.

I think it is a problem with the lens. Can anyone explain what seems to be the problem, and how I can fix it, if the problem is repairable.

  • 3
    Have you looked at the lens itself? Does it appear that the iris is closed down when the lens if off the camera? It sounds like the iris is stuck in a closed-down state (a high aperture number, which isn't really user-repairable), but you'd need to check.
    – user2719
    Feb 1, 2014 at 6:06
  • The aperture looks permanently open. Feb 2, 2014 at 5:05
  • It's a long shot but check the connection between the camera and the lens. There could be dirt there although most likely this sounds like it needs a repair job
    – codedude
    Mar 2, 2014 at 6:27

3 Answers 3


Sounds like I've had exactly the same problem as you. I suspect your lens is fixed by now but I thought I'd add a comment for your information and anyone else interested :-)

We fixed my lens ourselves - nerve, concentration and patience was required! This was not a job for the faint hearted. I've just blogged our experience Fixed: error 99 with Canon EFS 17-85mm :-)

We followed the instructions from an excellent blog by Roman Paulov Canon 99 error or how to disassemble Canon 17-85 IS USM and replace diaphragm unit.


I have had this problem before and I had to send it to their Mumbai service center to get it repaired. The repair took almost 10 days. This was almost 2.5 years back and haven't have had a single problem since then. Had to send it to Mumbai, because there was no showroom in Pune at that time :)

Anyways, my suggestion would be to directly send it to the Canon center and get it fixed.

  • Thanks for replying. Do you have an estimate of the cost it took you then? Mar 3, 2014 at 12:53

Are you getting an Err 01, Err 99, or similar error message? In a situation like this, it's not unlikely that an error would occur.

In any case, the lens needs repair. The aperture diaphragm is probably damaged, and I highly doubt this is user-serviceable.

  • No, the display doesnt show any Err message. The processor can select best settings, but clicking the button doesnt close the aperture and click a picture. I have taken your advice into consideration, and will be dropping it to a repair center. Mar 3, 2014 at 12:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.