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02-23-2010, 09:32 PM   #1
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Sigma 100-300mm f/4 serious issues

I bought a second hand Sigma 100-300 f/4 the other day ......Unfortunately, I am having some serious issues with the lens. I think there may be some internal problems with it.

f/4 especially, often when focussed over a long distance, is producing some very disturbing results. The images are either very out of focus, or there is some internal issue with the lens, or both. Nowhere in the image is remotely sharp. I realise that zooms aren't their best at their extreme ranges, or wide open, but I'm not just referring to some softness, but absolutely unusable images.

What also leads me to believe that there may be some internal issue is that the lens, when pointed downwards in any way, is makes a very loud and disturbing grinding noise when autofocused (I'm using a Pentax K10D). You can also feel the grinding in the lens. I'm worried about using the autofocus (or even the lens) at all in case it causes damage.

Now, I have been in contact with the seller, who sounds very reasonable. He offered to have it back for a full refund, or to let me keep it at half what I paid for it.

Does anyone know what on earth is going on with this lens?

02-23-2010, 09:39 PM   #2
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It could be the MF/AF slider that's not fully engaged. I had this problem with the BIGMA (which is why I took it back in favor of the 100-300mm).

Put the lens in MF mode with the camera turned ON, then spin the focus ring all the way from left to right and then back again.

You should hear and feel a little click.

Put the lens in AF mode and see if that fixes it.

Take about 20 pics to verify the issue is fixed. If it's a faulty AF/MF switch then the pictures will start going out of focus again within 5 shots and the lens will hunt a lot for focus.
02-23-2010, 10:04 PM   #3
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Thanks for the info. Unfortunately didn't work. It's strange that the lens is fine, say 10 metres away at 300mm f/4, but shoot 500mm metres away, and although it autofocuses to infinity, the image is terrible
02-23-2010, 10:56 PM   #4
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Can you upload some crops?

Interested to compare to my copy of the lens.

02-23-2010, 11:00 PM   #5
tux
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Sounds like its faulty. You can pick the up on trademe for $60-80 NZD
02-23-2010, 11:07 PM   #6
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QuoteOriginally posted by tux Quote
Sounds like its faulty. You can pick the up on trademe for $60-80 NZD
Say WHAT?

A Sigma 100-300mm f/4 for $60-$80????

I paid $1900 (AU) for mine about 9 months ago.
02-24-2010, 06:22 AM   #7
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QuoteOriginally posted by CWyatt Quote
I bought a second hand Sigma 100-300 f/4 the other day ......Unfortunately, I am having some serious issues with the lens. I think there may be some internal problems with it.

f/4 especially, often when focussed over a long distance, is producing some very disturbing results. The images are either very out of focus, or there is some internal issue with the lens, or both. Nowhere in the image is remotely sharp. I realise that zooms aren't their best at their extreme ranges, or wide open, but I'm not just referring to some softness, but absolutely unusable images.

What also leads me to believe that there may be some internal issue is that the lens, when pointed downwards in any way, is makes a very loud and disturbing grinding noise when autofocused (I'm using a Pentax K10D). You can also feel the grinding in the lens. I'm worried about using the autofocus (or even the lens) at all in case it causes damage.

Now, I have been in contact with the seller, who sounds very reasonable. He offered to have it back for a full refund, or to let me keep it at half what I paid for it.

Does anyone know what on earth is going on with this lens?
I would ask the Sigma service for a repair cost estimate. What you describe does not sound good. And given the seller's reaction, I would assume, he knows that he also had issues and though it better to sell the lens off If the Sigma repair cost is within the limits of the 50% off offer, then fine, otherwise I would send it back.

Ben
02-24-2010, 06:23 AM   #8
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Just a side track question with in green auto mode and AFS with the selector of MF and slightly off focused 1/2 shutter pressed the af motor will lock on subject.IS this normal?

cheers

02-24-2010, 04:56 PM   #9
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QuoteOriginally posted by CrazyNuts Quote
Say WHAT?

A Sigma 100-300mm f/4 for $60-$80????

I paid $1900 (AU) for mine about 9 months ago.
To quote a well known Aussie movie: "He's dreamin". No way would one go for that here, actually the one in question is the only one I've ever seen on Trademe (our ebay).
02-24-2010, 05:39 PM   #10
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I bought mine new though, and at the time they retailed for $AU2400.

This was when our $ vs the US$ was down at 64 cents.

Yeah.....I paid a premium but god damn it's a sharp lens.
02-25-2010, 06:14 AM   #11
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funny this thread popped up when it did,as i feel im facing similar problems with mine.
although i dont get the loud grinding on af.
focusing on close subjets appears fine,but when i try autofocusing on something a little further away i can see quite clearly through the viewfinder its out of focus
i can turn the focus ring a little and it appears in focus,then half depress shutter
and it focuses slightly out?
manual focusing seems ok,but from what i hear this lens should be sharp.
and it doesnt really seem that sharp,especially at f/4.
im pretty sure im experiencing some sort of focus issue with this lens.
every other lens on my k-7 locks its af accurately...what gives.
well im going to send this to cr kennedy for a service anyway.
here is a sample of mine at f/4 1/500th autofocused on the piece of grass sticking up in the middle
Name:  _IGP4037 copy.jpg
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02-25-2010, 06:33 AM   #12
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My 100-300mm f4 seems fine but I had that very problem with a Tamron 24-135mm SP lens that I dropped. It would lock focus up until around 50mm but after that no chance and if I manual focused with it then it was terrible, all out of kink.
02-25-2010, 02:29 PM   #13
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Lens is going back the the seller for a refund. Unfortunate as it was a bargain, but no point in a bargain lens that doesn't work! Think I might get the Pentax 60-250 f/4 instead now...
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