dust on sensor, hot pixels or what? (E-P1)

Discussion in 'Olympus Cameras' started by dreilly, Jan 9, 2011.

  1. dreilly

    dreilly Mu-43 Rookie

    14
    Jul 26, 2010
    I was processing some images from a restaurant shoot I did with an E-P1 and I found myself, "Gosh, that image looks like I shot it on film."

    A little more staring at it and I realized why...there was dust on it! Little white spots to be exact, flurries if it were snow. It was actually on all the images, not just that one, though in most cases it was not noticeable at all.

    I thought "hot pixels" were red. I thought the E-P1 had that dust-shake sensor dance thing going on. What am I seeing?

    I shot some test shots and they were still there. Cleaned the Panny 20's rear lens...still there. Did pixel mapping...still there. Is this sensor dust?

    (in the sample pic, you can see it especially in the dark area in the middle foreground). Like dandruff...

    Doug
     

    Attached Files:

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  2. shoturtle

    shoturtle  

    823
    Oct 15, 2010
    try the pixel mapping to see if it gets rid of it. If it is dust, clean the sensor it is pretty easy with the sensor clean kits.
     
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  3. Fiddler

    Fiddler Mu-43 Veteran

    I don't know about the dust, but it's a very nice photograph. Hope you can clear up the problem.

    All the best,

    Colin
     
  4. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    What ISO were you at? Looks like it could be noise ...
     
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  5. dreilly

    dreilly Mu-43 Rookie

    14
    Jul 26, 2010
    I was probably at 1600. But would noise look so much like...dust? I'm used to chroma and luminance noise but this is very specific spots and the same spots from image to image, as well. I tried pixel mapping. Still there.

    Anyone else positively ID this as dust on the sensor?

    thanks so much for the comments (and the compliment on the photo). Restaurants are rich subjects, even when they're terribly lit with florescent light.
     
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  6. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    Testing for dust

    The best way to test for dust is to shoot a uniform subject (blue sky works well), with a very small aperture (e.g. f/22) at low ISO (100) and the lens defocused (switch to manual focus, turn it to minimum focus distance). Dust will show up crisply as small dark ovals - usually a few dozen pixels in diameter.

     
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  7. Phaedrus

    Phaedrus New to Mu-43

    9
    Jul 18, 2010
    Noise it is, dust would appear as darker spots against a lighter background, that much is obvious.
     
  8. dreilly

    dreilly Mu-43 Rookie

    14
    Jul 26, 2010
    Dhazeghi's dust test indicates some dust. I guess I should clean the sensor.

    If it's noise, that's quite disturbing. I guess I could use the healing brush in LR to get rid of them, but one of the big bonuses of digital for me when I switched from film was no long hours doing dust and spot removal. Oh well!

    Thanks everyone!
     
  9. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    Looks like noise to me ... the spots are well defined (typically dust is OOF) and is most prevalent in the shadows/darker/underexposed areas.

    Gary
     
  10. Streetshooter

    Streetshooter Administrator Emeritus

    Dec 15, 2009
    Phila, Pa USA
    Would noise be consistent in every image?
     
  11. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    Sensor dust would be identical on every frame/file by location and size, I haven't any experience with the E-P1 at any ISO, but, if the noise/dust as exhibited in the example is noise then it would be present at every shot with similar ISO, metering and lighting conditions. Trying not to get too technical, but to answer the question, generally yes (unless the example was underexposed and the levels were boosted in post and all the other images were properly exposed ... then only the underexposed/boosted image would have noise ... or the underexposed image would have more noise than the images which were properly exposed). (Sigh ... hard to delivery a clear and concise answer due to all the variables ... even external heat, ala leaving the camera in the trunk of the car on a hot day will cause noise.)

    I have a GF1 and I found that for my tastes, ISO's above 800 would have noise beyond what I would consider acceptable.

    Dinner at ISO 800 w/ some noise reduction added in Aperture
    [​IMG]

    Gary

    PS- As a sidebar, I have found that a properly exposed higher ISO image would have less noise than an underexposed lower ISO image.
    G
     
  12. Streetshooter

    Streetshooter Administrator Emeritus

    Dec 15, 2009
    Phila, Pa USA
    Gary, my point was that noise would not be consistent from image to image in the same pattern. Dust would be but noise, I don't think so.
    You may have noise in every image but the pattern would not be consistent.
    don
     
  13. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    I agree.
     
  14. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    It depends on what you mean by consistent.

    If you mean the exact same pixel, no - but can you really tell if the noise is in one pixel, or the one immediately adjacent?

    If you took several pictures of the same/similar scene, the noise will likely be visible in the same dark areas and appear to be consistent,though.
     
  15. BillN

    BillN Mu-43 All-Pro

    Jan 19, 2010
    SW France
    This is dust - as Don said, each "spot" will be in the same place on every image taken - unless you disturb it with a brush (not recommended)

    dust.

    This is "noise"
    noise.
     
  16. stratokaster

    stratokaster Mu-43 All-Pro

    Jan 4, 2011
    Kyiv, Ukraine
    Pavel
    This is definitely the case and this is somewhat disturbing because it makes exposing for highlights difficult.
     
  17. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    Is it fair to say dust will always be a dark spot, and therefore more likely to show up on a light background, where noise will usually show as a light spot on a dark background?
     
  18. dreilly

    dreilly Mu-43 Rookie

    14
    Jul 26, 2010
    I went through my files on LR, zoomed in all the way. The USO (unidentified spotted objects) are in many but not all of the images. When they are present, however, they are always lighter and always in the same spot.
     
  19. Streetshooter

    Streetshooter Administrator Emeritus

    Dec 15, 2009
    Phila, Pa USA
    I would start by cleaning the sensor.
    It could even be dried condensation spots.
    Clean it then check a few files...
     
  20. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    Are they in low-ISO (say, 100-400) shots too? Or, is there any correlation between ISO and number of spots?