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Thread: Mysterious Black (ish) Blob

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    Mysterious Black (ish) Blob

    I have been doing some time lapse photography of clouds in the past few days. I have noticed a strange blurred blob near the middle of the screen. It appears on every shot in a sequence- although not in all sequences. The GH4 camera is new. Lens is a standard 14/140. I can't believe this is dust. Has anyone any ideas what this could be?

    I am not able to post a link to the image. The blob is fuzzy, circular and near the middle of the screen; but slightly to the right of centre.

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    Re: Mysterious Black (ish) Blob

    Out of interest what f stop are you using. It may be on the back of the lens and if you are at a small aperture the sensor may pick it up(lets hope it is not inside the lens).
    Have you another lens you can try?
    All the best

    Andy

    E1,E5,E420,OM1(N),14-54,12-60SWD,7-14,50-200,50mm F2 macro,25mm pancake,EC14,Sigma 50-500,OM50mm(F1.8),OM28mm(f2.8),FL36,HLD4,HLD2,Epson P3000,Manfrotto 680b monopod,crap tripod,various filters/CF cards.


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    Re: Mysterious Black (ish) Blob

    I'm using F22. The idea being I'd like the individual shots to be slightly blurry. That gives me around an eighth of second exposure which is what I need.

    I'm doing some tests as I write. I am trying to determine why only some sequences have the blob. Could it be that in most cases I was focussed on infinity?

    By the way Andy it's the only lens I have for the GH4.

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    Re: Mysterious Black (ish) Blob

    I can't explain why it's not on all your pictures but if there is something on the lens then at that aperture it will come into play.
    Try a picture of a clear sky and see if you can see it on there.
    All the best

    Andy

    E1,E5,E420,OM1(N),14-54,12-60SWD,7-14,50-200,50mm F2 macro,25mm pancake,EC14,Sigma 50-500,OM50mm(F1.8),OM28mm(f2.8),FL36,HLD4,HLD2,Epson P3000,Manfrotto 680b monopod,crap tripod,various filters/CF cards.


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    Re: Mysterious Black (ish) Blob

    I've just seen the blob in the viewfinder. So- I set up a shot at F4 and there was not blob. Same shot at F20 and there it is. Right. The greater the depth of field the more obvious the blob is. I expect this is a physical speck of dust. The next thing I need to determine is where it is. Is it on or in the lens? or is it on the image sensor?

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    Re: Mysterious Black (ish) Blob

    Glad you're getting there. I bet it's on the lens.
    All the best

    Andy

    E1,E5,E420,OM1(N),14-54,12-60SWD,7-14,50-200,50mm F2 macro,25mm pancake,EC14,Sigma 50-500,OM50mm(F1.8),OM28mm(f2.8),FL36,HLD4,HLD2,Epson P3000,Manfrotto 680b monopod,crap tripod,various filters/CF cards.


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    Re: Mysterious Black (ish) Blob

    I've taken a long hard look at the lens and cleaned the outer section. Can't see a thing. I've also stumbled upon the 'Clean Sensor' function in the GH4 menu. That has appeared to work. I can no longer see the blob in the viewfinder,,,,, but then I may just be kidding myself. I'll run another F22 test and see what happens. Thanks for your thoughts Andy.

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    Re: Mysterious Black (ish) Blob

    If there is anything in the light path you can be sure you will see it when you select f22. Is there anything on the sensor's front filter glass?
    Ross
    I fiddle with violins (when I'm not fiddling with a camera).
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    Re: Mysterious Black (ish) Blob

    Thanks Ross.

    So far the blob begins to appear at around F11 and is quite visible by F22. It matters not if I focus on infinity or close-up. The strength of the blob is dependent on the F stop. (Higher values equal stronger visibility of blob).

    As a newcomer to the GH4 (and mirrorless) I suspect that there is a speck of dust on the sensor. The sensor cleaning function on the GH4 did not remove it (although I previously believed it had).

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    Re: Mysterious Black (ish) Blob

    Quote Originally Posted by piranesi View Post
    Thanks Ross.

    So far the blob begins to appear at around F11 and is quite visible by F22. It matters not if I focus on infinity or close-up. The strength of the blob is dependent on the F stop. (Higher values equal stronger visibility of blob).

    As a newcomer to the GH4 (and mirrorless) I suspect that there is a speck of dust on the sensor. The sensor cleaning function on the GH4 did not remove it (although I previously believed it had).
    To me it wouldn't be something I would've suspected but expected with those symptoms. I would try a rocket blower first as it may be all you need.
    Ross
    I fiddle with violins (when I'm not fiddling with a camera).
    Cameras: OM-D E-M1 & Mk II, Olympus Stylus 1, OM-D E-M5.
    Lenses: M.ZD12-40mm f2.8 PRO Lens, M.ZD40-150mm f2.8 PRO Lens with MC-14, M.ZD12-50, M.ZD60 Macro, M.ZD75-300 Mk II, MMF-3, ZD14-54 II, Sigma 150mm F2.8 APO Macro DG HSM.
    Flashes: FL36R X2, FL50R, FL50.
    Software: Capture One Pro 10 (& Olympus Viewer 3).

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