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Sigma HSM AF slows when hotter

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Hoffy View Drop Down
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Post Options Post Options   Quote Hoffy Quote  Post ReplyReply Direct Link To This Post Topic: Sigma HSM AF slows when hotter
    Posted: 23 February 2012 at 03:52
Howdy,

Iím curious to see if anyone else around here is having or had the same issue. I have had my Sigma 70-200 F2.8 II EX DG APO HSM a little while (late 2008). I have quite enjoyed using the lens, but it hasnít had as much of a work out as I would have liked.

Anyhow, I have been using it a bit more regularly of late and have noticed a fault that is now becoming frustrating Ė when using it outdoors and it heats up, the auto focus noticeably slows and at some points even stops. Once everything cools down a bit, all appears to return to normal. I was using it at lunch time today, where it was around 33deg C ambient outside. It took about half an hour from being outside to see the AF slow. From a rough count in my head, it was taking about a 3rd longer to go from infinity to close focus. If I was outside longer and the lens got a chance to heat up more, I am sure it would have nearly ground to a halt. Iíve been back inside about an hour now and operation is normal.

Manual focus is fine, so its not the mechanism binding.

I have spoken with a few Motorsport togs that I know who use this lens and other Sigma Lenses (but other mounts) and some have reported the same issue. One of these guys had a particular lens (300 F2.8 Ė not an insignificant lens) repaired under warranty a few times and the problem still persists. He still uses the lens but has been known to put it in the fridge or a cooler from time to time to keep it cool.

I have contacted the local importer/official repair centre and in a round about way they indicated that they have fixed one or two lenses for undefined auto focus faults (I.E., yep, it happens, but we are not going to admit to it over the phone) and it may cost around $250 aus to get repaired. The tech I spoke to on the phone also suggested that Ďa lot of electronic devices wonít work well in that temperatureí (the first time I noticed it, it was in the mid to high 30ís outside).

What I would like to know is if others here have had similar issues as well. What have you done to resolve it? One thing that I have been considering (apart from repair) is getting a white (dammit!) lens coat and seeing if this would reduce internal temps enough to keep the lens operational when it gets hotter.

Thoughts?
 



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analytical View Drop Down
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Post Options Post Options   Quote analytical Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 04:42
Originally posted by Hoffy Hoffy wrote:

What have you done to resolve it? One thing that I have been considering (apart from repair) is getting a white (dammit!) lens coat and seeing if this would reduce internal temps enough to keep the lens operational when it gets hotter.
Depends on where the heat is coming from. If it's internal heat from the motor that doesn't radiate away as quickly in high ambient, then a lens coat will just hold it in.

A white color would only help if the source of the heat is direct sunlight.                 
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Bob J View Drop Down
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Post Options Post Options   Quote Bob J Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 06:17
Have you tried putting a fresh battery in once it is focusing slowly? Just wondering if the load is too much over time...
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Hoffy View Drop Down
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Post Options Post Options   Quote Hoffy Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 06:55
I'm pretty sure that its heat build up from the outside in that is causing the issue. I have been sitting here for the last half an hour with the lens cap on, running the focus backwards and forwards and there is no discernable difference in rack speed (I.E, infinity to close back to infinity).

I have also thought of the batteries Ė at the moment the lens is on my 7 film camera and the batteries are showing as full. I also tried it on the A700 with batteries from 100 down to 70%. Iíll give it a try and see how that goes.

I suppose what I could do is make a Ďpaperí lens coat (or even one out of an old white T shirt) and see if that makes a difference as well
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Hoffy View Drop Down
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Post Options Post Options   Quote Hoffy Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 10:59
I have just done a bit of googling and came across this youtube video:

http://www.youtube.com/watch?v=K4v35lYR1AU

I thought that this was blindingly faster then mine AF wise, but I then did actual focus tests and found that mine was kinda similar but a bit slower - but then again, I am inside, its night and I am just testing by focussing on a lamp and then the computer monitor.

If anyone has one of these lenses, can they tell me how it fares?

EDIT - removed my rant after some more testing!

Edited by stiuskr - 23 February 2012 at 12:12
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godsakes View Drop Down
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Post Options Post Options   Quote godsakes Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 12:41
Originally posted by Hoffy Hoffy wrote:


If anyone has one of these lenses, can they tell me how it fares?


No issues with overheating in the UK

personally I find the AF speed really good on the sigma in real world use - if you just let it cycle through it's entire range then it seems a little slow but in real life use it locks on straight away to your subject. The sigma's AF speed/accuracy is more dependable than the minolta 80-200mm f2.8 (back version) I also have
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Hoffy View Drop Down
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Post Options Post Options   Quote Hoffy Quote  Post ReplyReply Direct Link To This Post Posted: 23 February 2012 at 23:58
Originally posted by godsakes godsakes wrote:

Originally posted by Hoffy Hoffy wrote:


If anyone has one of these lenses, can they tell me how it fares?


No issues with overheating in the UK

LOL! I remember living through a London Heatwave when I was there in the mid 90ís. I donít know how you guys survived the 3 days about 30deg C! ;-)


personally I find the AF speed really good on the sigma in real world use - if you just let it cycle through it's entire range then it seems a little slow but in real life use it locks on straight away to your subject. The sigma's AF speed/accuracy is more dependable than the minolta 80-200mm f2.8 (back version) I also have

I played with the lens this morning before coming to work and most certainly it performs stella in daylight, so maybe my (deleted) rant was possibly unjustified. Anyhow, I still have the issue with the AF slowing (and I am talking crawling here) in the heat, so I do think it is probably best to get it fixed. I now need to decide whether I use the local repairer who is not the official sigma repair office or send it to the official repairer and get it flashed for SLT usage (for a camera that I donít own yet and probably wonít own for a few years to come)

Cheers
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