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Old Apr 1, 2005, 10:06 PM   #1
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Just wanted to share the problem I have been having going with cheaper lens.
I first bought the sigma 18-125 and returned it because it had particles inside the lens that left constant black spots on the pictures. I could actually see them when removing the lens from the camera and looking through it, zoom fully extended.
I returned that one and bought the counterpart from quantary. Same problem, dirt inside the lens on one of the intermediate glass pieces, leaving spots.
Do you usually test your lens by looking through them to check dirt inside?

[img]IMGtest.jpg[/img]
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Old Apr 1, 2005, 10:41 PM   #2
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Are you sure it's the lens?

Particles in the lens usually do not show up on the pictures - could it be dust on the sensor instead?
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Old Apr 1, 2005, 11:32 PM   #3
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I can see particles inside the lens, but as well, i think i see a couple spots on the sensor that do not blow off when I clean it. I am bringing my XT tomorrow to the shop and have them inspect it.
Now, I am wishing that it is only the lens.
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Old Apr 2, 2005, 6:38 AM   #4
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FYI - http://www.stevesforums.com/forums/v...69&forum_id=65

It has nothing to do with cost... Next time look for lenses which have internal zooming and internal focus - Theses lenses barrel stays relatively constant when zooming and AF as compared to compact lenses that can contract and expand to almost double/triple their lenght, like an accordion, creating a vacuum effect inside the lens which can pull in all kind of junk from the surrounding air

-> The good thing is dirts on the lens rarely show up on the image since they are not close to the focal plane as particles on the sensors...
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Old Apr 2, 2005, 7:12 PM   #5
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I went to the local ritz, they let me try the camera with other lenses. The same 8 points showed up at the same places, regardless of the lens (incidentally, the spots showed the most when using the 18-55, from canon).
The rep told us that the first batch of canon XT could have some 40% return rate due to sensor defect, it was almost a beta version. The sensor is the problem and he could not clean it, only canon services could perform the cleaning.
Now, should I have the XT exchanged or just repaired?
Good thing that I live 10 minutes from the repair center.

As well, to straigthen out things, I rescind any judgement passed on the sigma or quantaray as they were not the origin of the problem.
[img]IMG_0261.jpg[/img]
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Old Apr 3, 2005, 8:17 PM   #6
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Stoopid question: can I take a picture w/o a lens to test for this? (I'm still waiting for my lenses to come in...:roll
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Old Apr 3, 2005, 11:32 PM   #7
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ccfoo wrote:
Quote:
Stoopid question: can I take a picture w/o a lens to test for this? (I'm still waiting for my lenses to come in...:roll
Yes - unless it's too bright you won't be able to see anything -> use the -2..-1..v..+1..+2 scale on the camera and dim the ambient light accordingly to keep the marker centered on the 'v'...
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Old Apr 4, 2005, 12:27 AM   #8
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Try these resources for info and tools for sensor cleaning:
http://www.robgalbraith.com/bins/con...id=7-6460-7296
http://visibledust.com/sensor_cleaning_products.html
http://www.ultimateslr.com/clean-image-sensor.php
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