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Sigma 100 -300mm F4 focus problem.


bailey73 e2
11 357
15 May 2011 9:02PM
I bought a 100-300mm lens off Ebay a couple of months ago and as soon as it was delivered I gave it a check over and tested it.. Everything appeared fine.

Recently I have noticed an intermittent focussing problem where the lens will stop tracking a moving subject and just stop focussing.. It will still let you take a shot but obviously the shot is then out of focus. Once the lens has stopped focussing it is an absolute pain to get it started again, I have tried switching the camera off/on, manually zooming in/out, manually focussing and taking the lens off the camera until it eventually springs into life again.

Several times now I have also noticed the lens make a short whiney noise so im thinking that there is a problem somewhere with the HSM as the focussing also appears to be slower than before.

I was going to be sending the lens off to Sigma for a service this week but now I feel it requires more than that so I just wondered if anyone else on here had suffered a similar problem the a 100 - 300mm and what was the cause.

Cheers

Darren

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justin c e2
11 4.6k 36 England
15 May 2011 9:12PM
It doesn't sound like there's a problem. Lenses will often not focus if there's insufficient contrast or there's confusion on what it should actually be focusing on. The same with focus speed, it can vary from shot to shot, situation to situation, it depends on the subject contrast, light levels, etc. etc.
Overread e2
6 3.9k 18 England
15 May 2011 9:19PM
Hmm but normally if a lens won't AF because of lack of light or contrast it will end up hunting if you just press the AF button again. Might it be that you've enabled some custom function within the camera to tell it to cut out AF if it fails to get a lock?

Otherwise it sounds a little like it might have an AF problem outside the general lack of ability to get a lock - esp if its proving hard to get going again after.


For what its worth most AF motors will whine a bit more when the lens is at a more sharp upward or downward angle (depending on which way the internal elements are being moved).
justin c e2
11 4.6k 36 England
15 May 2011 9:22PM

Quote:Hmm but normally if a lens won't AF because of lack of light or contrast it will end up hunting if you just press the AF button again.


Not always. They do occasionally just refuse to try to focus.
tomcat e2
9 6.2k 15 United Kingdom
15 May 2011 9:26PM
If it won't do the biz after rebooting, then I would suggest that there is a problem.
15 May 2011 9:33PM
Try cleaning the contacts on the lens & camera, google is your friend
bailey73 e2
11 357
15 May 2011 9:38PM
The focus issue is progressively getting worse.. I took 889 shots yesterday and only 8 were sharp where as more than 75% were sharp out of 1100 when I first noticed a problem 3 weeks ago. The lens doesn't hunt it just stops responding and I have reset the camera and checked all the settings but it just doesn't want to know.

I have owned a 100-300 before and it never gave me any problems.
bailey73 e2
11 357
15 May 2011 9:39PM
I have cleaned the contacts on both camera and lens and the problem was still there.
justin c e2
11 4.6k 36 England
15 May 2011 9:53PM

Quote:I took 889 shots yesterday


How many!! Sounds like you've worn it out WinkTongue


Quote:and only 8 were sharp


That's not a bad hit rate for a Sigma!!Wink
bailey73 e2
11 357
15 May 2011 10:18PM

Quote:I took 889 shots yesterday

How many!! Sounds like you've worn it out WinkTongue

and only 8 were sharp

That's not a bad hit rate for a Sigma!!Wink



Grin

It is probably one of the sharpest Sigma lenses I have ever had so it is such a shame that a fault has developed.

I normally take about 1000/1500 shots at motorsport events so the kit does work hard but it does get sent off for cleaning and servicing.
Overread e2
6 3.9k 18 England
15 May 2011 11:38PM

Quote: That's not a bad hit rate for a Sigma!!Wink


My (sigma) macro lenses would like a word with you TongueGrin
16 May 2011 11:22AM
If cleaning the contacts does not work it likely needs a new AF motor.
Whether the seller suspected the motor might be about to fail before selling it is unknown.
I am guessing you have taken a few thousand shots with it so after 2 months you cannot fairly go back to a private seller.
Sales from camera shops usually carry a 3 or 6 month warranty.
justin c e2
11 4.6k 36 England
16 May 2011 8:17PM

Quote:My (sigma) macro lenses would like a word with you TongueGrin


I'm only kidding. If I ever decide to go for a longer macro lens, the Sigma would be top of my list Smile
bailey73 e2
11 357
27 Aug 2011 8:32PM
Thanks for all your replies.

The lens came back from Sigma in just under 6 weeks and at a cost of 180 the A/F drive unit was replaced.. I have used the lens once since it came back and it has now packed up again (less than 10 shots) Sad

I can hear a very faint click when I try and auto focus but the lens just doesn't want to know.. I am gutted, I will have to send it back to Sigma again I suppose.
JackAllTog e2
5 4.0k 58 United Kingdom
27 Aug 2011 10:02PM
Ouch, that's gotta go back - sounds like they did not replace all the affected components. Hope its quicker this time around.

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