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Thread: black spot

  1. #1

    Default black spot

    i got a sigma (canon mount) from one of the guys in this fourm today. got 1 week personal warranty.. it seems fine until i notice some dust? or specks or something in the lens.. at 3.5 fstop picture taken is ok... but at fstop 22 and above there is a black spot.

    where can i find a service centre? and how much is it roughly? anyone service sigma lenses before?

  2. #2

    Default Re: black spot

    Is the black spot IN the lens, or just shows up on the photo at f/22?

    Better yet, do you have a photo of the lens dust, and the sample photo taken at f22 and above?

  3. #3

    Default Re: black spot



    fstop at 40, zoom to 200mm



    fstop at 3.5, 18mm
    Last edited by wtm78; 4th March 2009 at 12:51 AM.

  4. #4

    Default Re: black spot

    Quote Originally Posted by wtm78 View Post


    fstop at 40, zoom to 200mm



    fstop at 3.5, 18mm
    Eh, that's just dust. Get yourself a proper blower.
    Alpha

  5. #5

    Default Re: black spot

    Quote Originally Posted by Rashkae View Post
    Eh, that's just dust. Get yourself a proper blower.
    i blow and wipe the lens already le... still like that... if the dust is inside the lens how??
    Last edited by wtm78; 4th March 2009 at 12:55 AM.

  6. #6

    Default Re: black spot

    It looks more like sensor dust to me.

    Dust in the lens has to be super duper intrusive to make those kind of marks.

    But then again, if it's on the sensor, it would not matter what focal length is used; the size of the dust would look the same in the photo.

    Sigma has a service center at Bukit Merah. Also, some of the competent repair shops around the Peninsula area should be able to do a cleaning job since you already tried.

  7. #7

    Default Re: black spot

    Quote Originally Posted by Dream Merchant View Post
    But then again, if it's on the sensor, it would not matter what focal length is used; the size of the dust would look the same in the photo.
    He did the normal aperture testing, not focal length; the dust only shows up on the smaller apertures, so it's most likely sensor dust.
    Alpha

  8. #8

    Default Re: black spot

    Quote Originally Posted by Dream Merchant View Post
    It looks more like sensor dust to me.

    Dust in the lens has to be super duper intrusive to make those kind of marks.

    But then again, if it's on the sensor, it would not matter what focal length is used; the size of the dust would look the same in the photo.

    Sigma has a service center at Bukit Merah. Also, some of the competent repair shops around the Peninsula area should be able to do a cleaning job since you already tried.
    you have any idea how much the price? should i return the lens since he gave me 1 week warranty?

  9. #9

    Default Re: black spot

    Quote Originally Posted by wtm78 View Post
    i blow and wipe the lens already le... still like that... if the dust is inside the lens how??
    It's not in the lens. You have dust on the sensor. Your camera manual, as well as 1000 sites on the web, can teach you the basics of cleaning your sensor using a blower.
    Alpha

  10. #10

    Default Re: black spot

    Quote Originally Posted by Rashkae View Post
    He did the normal aperture testing, not focal length; the dust only shows up on the smaller apertures, so it's most likely sensor dust.
    so its not the lens? its the camera? but i do see dust when i see through the lens
    Last edited by wtm78; 4th March 2009 at 01:03 AM.

  11. #11

    Default Re: black spot

    Quote Originally Posted by wtm78 View Post
    so its not the lens? its the camera?
    Yes. Dust on the sensor. Try to mount a different lens and test at f/22. If you have the same spots, it's dust on the sensor. If you get no spots, then it's something that's deeply ingrained in the lens (almost never heard of that though)
    Alpha

  12. #12

    Default Re: black spot

    Quote Originally Posted by wtm78 View Post
    so its not the lens? its the camera? but i do see dust when i see through the lens
    Dust in a lens is normal.
    Alpha

  13. #13
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    Default Re: black spot

    Quote Originally Posted by wtm78 View Post
    so its not the lens? its the camera? but i do see dust when i see through the lens
    looks like dust on sensor. most of the time small speck of dust in lens will not affect or show up in picture... most common sense thing to do now is to swap another lens and shoot again at high f-number... the black specks will still be in the same location...

  14. #14

    Default Re: black spot

    Quote Originally Posted by Rashkae View Post
    Yes. Dust on the sensor. Try to mount a different lens and test at f/22. If you have the same spots, it's dust on the sensor. If you get no spots, then it's something that's deeply ingrained in the lens (almost never heard of that though)
    Quote Originally Posted by andrewtansj View Post
    looks like dust on sensor. most of the time small speck of dust in lens will not affect or show up in picture... most common sense thing to do now is to swap another lens and shoot again at high f-number... the black specks will still be in the same location...
    i use another lens shoot at high f-number.. the specks are at the same place. so its the sensor?

  15. #15
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    Default Re: black spot

    Quote Originally Posted by wtm78 View Post
    i use another lens shoot at high f-number.. the specks are at the same place. so its the sensor?
    yes, search online or read your instruction manual on how to go about cleaning your sensor.

  16. #16

    Default Re: black spot

    Quote Originally Posted by wtm78 View Post
    i use another lens shoot at high f-number.. the specks are at the same place. so its the sensor?
    You can also send it to the service centre for camera's sensor cleaning. Just prepare a fee for such service, if you still can't get it off. I sent mine for service (since still under warranty, so cleaning is free), getting it back soon.

  17. #17

    Default Re: black spot

    Ahh ... I missed the detail where at 18mm it was shot at f/3.5! My bad!

    YEs, 'sensor' dust. One easy way I discovered is to use a NEW lenspen to clean the hi-pass filter in front of the sensor after blowing. Check your instruction manual how to open the shutter to blow and clean your sensor.

    If after reading all the online articles about hi-pass filter cleaning, you're not sure or don't feel confident, you can bring your camera back to the service center to get it cleaned for a fee. But be sur to CHECK on the spot using the f/22 method and a laptop, because no service center has a clean-room environment.

  18. #18
    Senior Member darrrrrrrrrr's Avatar
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    Default Re: black spot

    dust specks in the lens are normal and do not affect our photos.

    dust specks on the glass filter just on top of the sensor will cast a defined shadow on the sensor sites at small apertures (e.g. f/22), that's why u see the black spots. again, this is normal.

    activate the mirror-up for sensor cleaning and use the blower to try to dislodge the dust. should work in most cases.. if not send for professional cleaning or DIY.
    Last edited by darrrrrrrrrr; 4th March 2009 at 01:47 AM.

  19. #19

    Default Re: black spot

    With reference to the two pictures, in checking the sensor cleanliness, do we just shoot and do a preview (without magnifying) the image or should the preview be seem with a magnified view?

    Which is the right thing to do
    i.e. shoot 2 frames with a clear background, using what ever focal lens at f22 and just do a standard preview. If it shows foreign dots at the same location on both frames, sensor is dirty.

    or do the same above and magnify it to say, 80% enlargment in the preview and browse to scan for dots?

    Advices from the Shufu are appreciated.


    Quote Originally Posted by wtm78 View Post


    fstop at 40, zoom to 200mm



    fstop at 3.5, 18mm

  20. #20
    Moderator catchlights's Avatar
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    Default Re: black spot

    Quote Originally Posted by Staro View Post
    With reference to the two pictures, in checking the sensor cleanliness, do we just shoot and do a preview (without magnifying) the image or should the preview be seem with a magnified view?

    Which is the right thing to do
    i.e. shoot 2 frames with a clear background, using what ever focal lens at f22 and just do a standard preview. If it shows foreign dots at the same location on both frames, sensor is dirty.

    or do the same above and magnify it to say, 80% enlargment in the preview and browse to scan for dots?

    Advices from the Shufu are appreciated.
    you can shoot just one frame, aim at any white area and fill the frame, DON"T HAVE TO BE IN FOCUS, SHOOT AT F22, if you are using P or A mode, dial in exposure compensation +1~+1 2/3, to make the white area in near white instead of mid tone gray.

    load the image into your computer, you can see any dust spots very clearly
    Shoot to Live, Live to Shoot
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