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 Post subject: Dust in lens?
PostPosted: Sun Oct 12, 2008 6:14 pm 
Hello,

A few months ago I bought a Sigma 18-200mm OS lens from a store in Taiwan, and things have been going great. However, I noticed that there are some spots when I shoot in smaller apertures. These are not dust spots on the sensor, but I believe spots on the internal lens. You can see them through the viewfinder. Despite having a UV filter to cover the lens cover, I suspect dust to have creeped in from the side. The good news was that in Taiwan you get 3 years of warranty with Sigma lenses, but unfortunately, I'm not in Taiwan anymore.

In Taiwan, there is a street dedicated to just selling cameras and lenses, it's an amazing place.

I also got a Sigma 150-500mm OS HSM lens from another seller. However, I noticed at 500mm it has big sharpness issues, and ghosting around the image. I also noticed some dust getting into the lens, despite using a UV filter, as with my 18-200mm. Is this a defect or is it normal with this lens?

I used to have a non-OS version of the 18-200mm. I used it with my old Rebel XTi/400D, but both fell in the water and it almost got wrecked! :cry: The dust and dried water in the lens was so noticable, there were sploches all over the lens. I was still forced to use it until I could get a new camera and lens. Even though some focus points don't light up anymore, it still worked, but I gave it to my dad along with the lens which was cleaned, as I got an XSi and an OS version of the same lens.

From what I heard, Sigma has good service, but some have complained about their quality control.

What should I do about these problems I'm having, since I'm not in Taiwan anymore?


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 Post subject:
PostPosted: Sun Oct 12, 2008 6:25 pm 
My best shot, would be that you should go to a good camera-store and have a pro look at it. He will be able to identify and adivce you, as he can physicly see it.

0eyvind

Btw, i imagine it's a great street :D


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 Post subject:
PostPosted: Mon Oct 13, 2008 4:01 am 
Thanks, but unfortunately in Canada, we don't have much camera stores. The closest to that is London Drugs, and they only sell half the amount of lenses that they have overseas.

Yeah I agree, the Bo-Ai Road Camera Street is very awesome. But in these places you should be careful of prices and gray marketing. I found the place with the lowest price for the 18-200mm OS, and they were able to clean that soaked non-OS lens.

Well I checked again, and nothing is wrong. I suspect that dust on and behind the UV filter is more visible than that inside the actual lens.

Today, I went to Granville Island and took some great pics of the sights there. Unfortunately, I cannot upload on Flickr because I cannot afford a pro account, and I haven't even uploaded the hundreds of pics taken in Taiwan this summer!


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 Post subject: Re: Dust in lens?
PostPosted: Mon Oct 13, 2008 10:09 am 
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Frankyboy5 wrote:
...These are not dust spots on the sensor, but I believe spots on the internal lens...

The only way that dust spots on the lens surfaces could appear in your photographs would be if the lens was actually creating a focussed image internally as well as externally on your sensor. While I can't be sure I find that a pretty unlikely scenario so I have to ask why it is you are sure the dust spots aren't on the sensor assembly. They may not be easily visible and I'd be tempted to follow the advice in Gordon's feature DSLR Tips Digital SLR dust workshop over at DSLR Tips before proceeding down alternative paths.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
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Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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 Post subject:
PostPosted: Mon Oct 13, 2008 11:13 pm 
Well I can see it through the viewfinder...

Perhaps it's just dust on the surface of the UV filter, but I can see some specks of dust inside the lens.


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 Post subject:
PostPosted: Tue Oct 14, 2008 12:00 am 
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.
Sorry, I see now that I didn't read your initial post carefully enough and I missed the fact that you can see the dust spots through the viewfinder. :oops:

As you say, if the dust spots you see through the viewfinder and those that appear in your pictures are in the same positions then the lens itself is the most likely culprit. I suppose you could try some vigorous zooming. Obviously you don't want to be too rough with the lens but if you are lucky any air currents induced inside the lens as a result might dislodge the dust. If that doesn't help then a factory service would be my next choice. Maybe your local Sigma office will smile kindly on you and offer the service under warranty. It's worth asking.

Is FAQ 2 on this Sigma page relevant? If you have a factory warranty card then it would seem you get a one year international warranty.

Bob.

_________________
Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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