Problem with 17-35 KM lens.

[andelain]

I can't believe it, this is my second prob in a month, after nearly 3 years of trouble-free shooting. First, thanks for your help on my last lens question, I hope that you'll be able to help with this.

Went out this afternoon, to make the most of the winter sun. I had the KM 17-35 on my 7D, and my wife had the 18-250SAL on her A700.

As I composed the first shot, and adjusted the aperture on the rear scroll wheel, the camera started whirring, for about 3 secs, and then it went dead, monitor too. I changed the battery, in case, demounted and remounted the lens, and switched on. Nothing.

I put the 18-250 lens on and took shot after shot without probs, including using the rear scroll wheel to adjust the aperture.

Switched back to the 17-35 and no probs, until I used the rear scroll wheel to adjust aperture. Same result, whirring sound followed by a dead camera. There clearly seems to be a malfunction between the body and the 17-35 lens. But why now, after 2 years of trouble free shooting with the same lens?

If it is a camera prob, I need to act soon, as my extended warranty expires in 2 months.

Please can you help?

Thanks.

Art.

[David Kilpatrick]

Clean your lens contacts with a pencil erase followed by a soft cloth. Right now it's the most likely source of the fault - dirty lens contacts.

David

[andelain]

David,

Thanks for your response. Will try your solution and report back.

In my "panic" I forgot to mention that the 17-35 lens worked fine on the A700, so perhaps it is more than dirty lens contacts.

Art.

[andelain]

David,

Things seem to be more complex than I thought.

I've cleaned the lens contacts, as you suggested. All seemed well, for about 8 shots, and then the whirring sound followed by a dead camera.

Tried other lenses with the 7D. It works fine with: 18-70 kit lens: 100 F2.8 100 SAL: 18-250 SAL.

It has problems with: 17-35 KM: 24-135 Sigma. With both these lenses, the camera produces the whirring sound and t hen dead. It is impossible to activate the camera until these lenses are removed, and one of the trouble-free lenses is mounted. It then boots up as normal.

All the above lenses work fine on the A700.

Clearly(?) there seems to be some "communication" problem between certain lenses and the body. Have you any further suggestions as to a possible solution? Please bear in mind that the problem lenses have funcioned fautlessly over the last two years. Could it possibly be the body running into probs?

Thanks.

Art.

[Dr. Harout]

Other reason I can think of is the looseness of the mount, so just tighten the screws that you see at the rear of the lens.

[David Kilpatrick]

Also, tighten up the body mount screws - these can come loose, not just the lens screws. However, by far the most likely other possibility is a voltage drop. By now, all the original lith-ion cells for the 7D will be showing their age. The charger offers no refresh mode, and won't do preventitive maintenance, the cells will eventually become unreliable (I have at least one which has reached that stage and I am cycling between half a dozen cells, shared by my 7D and A2). If you have a 6V (or maximum 7.2V) mains adaptor compatible with the 7D, it could be worth checking the camera's behaviour with DC supply.

That is is happening with two lenses, appears to be related to a moment where drain on the power is strong, and the lenses are both ones which have fairly stiff focus motors makes me think that battery condition could be a factor. Lith-ion cells can show sudden failure under load when old.

David

[Dusty]

That is is happening with two lenses, appears to be related to a moment where drain on the power is strong, and the lenses are both ones which have fairly stiff focus motors makes me think that battery condition could be a factor. Lith-ion cells can show sudden failure under load when old.

David

Perhaps a way to check that is to use them until they stop working, remove lens, and reboot w/ manual focus selected. That cuts out variables of different lenses.

Dusty

[andelain]

Thanks for your suggestions, everyone.

Lots of things to try. Will report on progress.

Thanks.

Art

[andelain]

It worked! Decided to start with the simple solution, ie., the battery. I have a new battery, charged it, and tried it. Worked a treat, with the 17-35 KM. No probs.

With the Sigma, the odd hiccup, but working 90% of the time. Not really bothered about the Sigma as it has hardly been on the camera since I got the 218-250SAL.

One other parameter to add. Our cameras are stored in a cool ,dry place. So, cameras were cold, lenses were cold, and, when I reported the prob, the batteries were cold. We were also outside, in winter. Now what I know about cameras, would fit on the head of a pin. But, I seem to remember reading that cold batteries do not perform particularly well (?).

Anyway, thanks, everyone, for your help. And thanks,David, for the battery suggestion.

Art.

[Dusty]

One other parameter to add. Our cameras are stored in a cool ,dry place. So, cameras were cold, lenses were cold, and, when I reported the prob, the batteries were cold. We were also outside, in winter. Now what I know about cameras, would fit on the head of a pin. But, I seem to remember reading that cold batteries do not perform particularly well (?).

Art.

Bingo! Batteries work via a chemical reaction. Chemical reactions slow down with the temperature. Keep your spares warm, and if you will have your camera off for quite some time in the cold, take out the battery and put it in a shirt pocket, inside your coat.

Dusty