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enter image description hereI recently sold my pro camera and lens and downgraded to an Olympus mirrorless. A used lens I bought, the Olympus M.Zuiko Digital 12-50mm, I have been doing long exposure shots with. Here is an example photo I took. Do you see the black smudgey area above the bottom rocks? These are not caused during editing, this is unedited. They are captured during the long exposure. What are they called?? Is my lens broken or is this fixable? My pro setup never had this problem. It is there in most of the long exposures I have taken.   So I have added a second photo. See the black streaks on the water above the black rocks in the middle of the picture? After further investigating, I realise these are only in the long exposure pictures I am taking when I use an ND filter. SO, that would mean these are being caused from the filter. What does that mean? Crappy filters??

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    I looks like reflection of the clouds - but I'd like to see another from the series to eliminate that. – Tetsujin Jun 10 at 16:15
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    Can you highlight the artifact you are concerned with, and possibly post a 1:1 crop? Like Tetsuijin I'm just seeing what's likely cloud reflections that are a little muddy due to underexposure. – mattdm Jun 10 at 16:16
  • So I have added a second photo. See the black streaks on the water above the black rocks in the middle of the picture? After further investigating, I realise these are only in the long exposure pictures I am taking when I use an ND filter. SO, that would mean these are being caused from the filter. What does that mean? Crappy filters?? – Ckdub Jun 10 at 16:52
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    Hi Ckdub, Welcome to Photography.StackExchange. We hope you enjoy sharing experience and knowledge. I see what looks like a photograph of clouds reflected in water. I read and re-read your post but don't see what smudges you discuss. Could you point (arrow) or encircle the smudge(s)? I grew up near large lakes, rivers, and the ocean. Your photos look normal to me. True; sometimes clouds can look like smudges. Meteorologist refer to those kinds of clouds during a pilot's weather briefing as "skud." Long exposures will tend to diminish sharp detail in moving subjects such as water and clouds. – Stan Jun 10 at 17:33
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    I think there is some artifact there but it is hard to see. To see if it is real take long-exposure pictures of a bit of white paper with a bit of black paper overlaying the bottom part of it. This will produce an idealised version of the dark rocks without any question of reflections. You can also try making pictures of chequer-patterns. I suspect this is a sensor artifact (it's unlikely to be the lens), perhaps related to heat or readout, but you need to remove all the factors which make it hard to see such as reflections and general detail in the image. – tfb Jun 11 at 16:48
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Not a problem with your equipment. They are reflections of the clouds. Non-smooth water will cause vertical smears. The effect is subtle here, but it is more obvious when the sun is reflected.

image

Edit: More evidence, an example of vertical smearing from my library:

Vertical Smearing example

Also note that the clouds in the sky in the OP's pictures are not blurred, so the exposure was not very long. It is not caused by a long exposure.

  • I'm not sure that's the problem area, in the first photo, further to the right above the rocks there's a distinct perfectly vertical set of blurry streaks. – Digital Lightcraft Jun 11 at 13:10
  • They are all caused by the same effect, some the vertical smears further to the right are caused by the trees. – Mattman944 Jun 11 at 14:17
  • The exposure is not long enough for the movement of the clouds to be blurry, but it is long enough for the movement of the water surface to blur their reflection. – Michael C Jun 12 at 7:17
  • @Mattman944 The only place the effect is seen are in areas that water is reflecting clouds. It seems to go above/below the reflection because at the extremes of the effect the water is only at the proper angle to reflect the cloud (instead of open sky) for a very short duration each cycle of the repetitive motion of the waves. – Michael C Jun 12 at 7:21

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