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Strange long exposure issue

Discussion in 'Olympus Cameras' started by soko, May 10, 2013.

  1. soko

    soko New to Mu-43

    8
    Apr 25, 2013
    Melbourne
    I was taking some long exposure shots last night and noticed when I used my Panasonic 20mm with the OM-D there were these random coloured pixels scattered throughout the image, for example like this: http://i.imgur.com/RE4qIoq.jpg

    Only happens when I use that lens, I hope its not broken ? :S
     
  2. soko

    soko New to Mu-43

    8
    Apr 25, 2013
    Melbourne
    By the way I'm referring to the pixels in the darker areas, ignore the light trail in the middle of the picture, thats an aeroplane.
     
  3. KVG

    KVG Banned User

    May 10, 2011
    yyc(Calgary, AB)
    Kelly Gibbons
    I had the same issue with my 20mm and 14mm where I would get red spots in dark areas and random white pixels that look like stars.
     
  4. FrayAdjacent

    FrayAdjacent Mu-43 Regular

    183
    Dec 5, 2012
    Austin, TX
    M@
    I see a few blue and a couple red spots in the ground area of the picture... I'd suspect some weird flare issue due to the lights. Does it happen if there are no sources of light directly in the frame? Are you using a hood to limit the possibility of light sources hitting the lens from outside of the frame?
     
  5. soko

    soko New to Mu-43

    8
    Apr 25, 2013
    Melbourne

    Only happens in the long exposure shots at night, other shots are fine, no hood used.
     
  6. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    John Griggs
    You need to turn long exposure noise reduction on. This is NOT filtering -- it's a common technique used in digital astro photography and won't degrade you image. Google "dark frame subtraction" to understand it.

    On your E-M5 it's here: Gear Menu --> G (Color/WB) --> Noise Reduct.

    Set it to AUTO or ON. I do a lot of long exposures doing urbex in dark buildings and I leave it in AUTO on my E-M5.

    Again I repeat: this is NOT noise filtering and doesn't hurt your images. It subtracts out hot pixels which is what you are seeing.
     
  7. RnR

    RnR Mu-43 All-Pro

    Sep 25, 2011
    Brisbane, Australia
    Hasse
    You should write an FAQ post on these forums entro. Seems this issue comes up often enough :)
     
  8. remoteman45

    remoteman45 Mu-43 Rookie

    22
    Apr 21, 2013
    Would you leave it on for shooting star trails with an intervalometer as well?
     
  9. FrayAdjacent

    FrayAdjacent Mu-43 Regular

    183
    Dec 5, 2012
    Austin, TX
    M@
    IIRC, enabling the noise reduction will add your shutter speed to the exposure processing. Basically it takes the shot, then records what the sensor sees with the shutter closed for the same amount of time, then subtracts the hot pixels from the image.

    A 30 sec exposure will be followed by a 30 sec pause as it does a closed exposure to map the hot spots.
     
  10. entropicremnants

    entropicremnants Mu-43 All-Pro

    Jul 16, 2012
    John Griggs
    As long as the doubled exposure times don't take you over the interval time, then yes if you want clean images.
     
  11. RobWatson

    RobWatson Mu-43 Hall of Famer

    I can tell you that building dark frames and manually correcting in post does not work as well as the in camera correction. It does work but just not quite as well. If one is pressed for time then a manual correction in post is possible.

    It is not a hard test to perform so one can prove it to themselves if needed.
     
  12. homerusan

    homerusan Mu-43 Regular

    130
    Dec 25, 2012
    izmir, TURKEY