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Sensor problem

Discussion in 'Olympus Cameras' started by homerusan, Mar 19, 2013.

  1. homerusan

    homerusan Mu-43 Regular

    130
    Dec 25, 2012
    izmir, TURKEY
    i have some problems with my e-pl2. last day i was shooting in one of my fav place with nd 10stop filter. first images seems ok like this..
    %100 crop from raw
    ChXtepX.

    after an hour while i was continue to shot i got this image...

    %100 jpeg crop
    V3g5eEM.

    %100 raw crop
    74FzvaA.

    even in raw file has some white points like artifact.

    i only shot about 1 hour with some breaks. is it normal?
     
  2. cprevost

    cprevost Mu-43 Regular

    59
    Oct 31, 2012
    Hard to tell? I'm assuming you had a really long shutter speed with the 10 stop ND filter. I'd try some long exposures without the filter to see if you get the same effect.
     
  3. homerusan

    homerusan Mu-43 Regular

    130
    Dec 25, 2012
    izmir, TURKEY
    shutter speed was 125 second
     
  4. fuSi0n

    fuSi0n Mu-43 Regular

    37
    Jan 11, 2013
    Bavaria, Germany
    The pixels are hotpixels and the camera has an option to automatically remove them (dark frame image substraction) The option is somehwere in the main menu, best is to habe a look in the manual. These pixels are caused by the "warm" sensor during long exposures.
    And your tripod seems to be not the sturdiest construction ( from the blur of the first image).
     
  5. Rockinggoose

    Rockinggoose Mu-43 Regular

    Sensor overheating. I seem to remember the manual describes this and recommends switching off to allow it to cool down.

    David
     
  6. kwalsh

    kwalsh Mu-43 Top Veteran

    775
    Mar 3, 2012
    Baltimore, MD
    As others pointed out probably the sensor getting hot. If the temperature outside is warm, the camera is in the sun and it is powered on for an extended period of time you can get more "hot pixels". That said, I'm surprised at 1/125 shutter speed to see so many of them. Usually this is more of a problem at longer shutter speeds.
     
  7. RevBob

    RevBob Super Moderator

    Jun 4, 2011
    NorthWestern PA
    Bob
    Either it was very hot, the OP took a LOT of photos or the sensor is starting to break down. Or a combination of some of these.
     
  8. RobWatson

    RobWatson Mu-43 Hall of Famer

    Sun shining into the lens also brings much heat. NIR/IR filters can only do so much. Bet it returns to normal after a cool down period.
     
  9. fuSi0n

    fuSi0n Mu-43 Regular

    37
    Jan 11, 2013
    Bavaria, Germany
    The shutterspeed was 125 seconds not 1/125 s. He was unsing a 10 stop ND filter. When i turn off the dark frame compensation i get the same amount of hot pixels nothing to worry about.
     
  10. homerusan

    homerusan Mu-43 Regular

    130
    Dec 25, 2012
    izmir, TURKEY
    Thanks for the answers. Yes it was 125 sec not 1/125. i wonder if omd has this kind of problem or not. Because i am searching for weeks to get one.
     
  11. fuSi0n

    fuSi0n Mu-43 Regular

    37
    Jan 11, 2013
    Bavaria, Germany
    EVERY CCD/CMOS based camera has this Problem even a Canon 5D III. Its a physical property of every senor when it is heating up. When you dont switch on the camera setting to compensate this noise, even the OMD will not overcome the problem....
    Its not a camera problem!
    Google CMOS + Hot pixel + dark frame....
     
  12. kwalsh

    kwalsh Mu-43 Top Veteran

    775
    Mar 3, 2012
    Baltimore, MD
    Ah - 125 sec. Yes, those are hot pixels. Every camera of every make will have them. There will be more and they will be brighter if the camera is warm. Even a cooled CCD array for astrophotography will have them. Unavoidable.
     
  13. wonglp

    wonglp Mu-43 Veteran

    395
    Feb 28, 2011
    Singapore
    All pen/em5 has this hot pixels problem. Turn Noise Reduction on will reduce this though not completely at times.
     
  14. RobWatson

    RobWatson Mu-43 Hall of Famer

    Not hot pixels.

    A warm sensor will have higher levels of dark current. Perfectly normal.

    Use the noise reduction setting (manual pp89) to reduce the dark current effects.

    Every sensor on the planet (even the ones in space) has this property.

    Be aware that even with noise reduction enabled there will still be residual noise that may need filtering. The noise reduction feature actually does not reduce noise but it does remove most of the dark current signal.
     
    • Like Like x 1
  15. kwalsh

    kwalsh Mu-43 Top Veteran

    775
    Mar 3, 2012
    Baltimore, MD
    OK, yes I guess an ambiguous term - "hot pixel" vs "stuck pixel" vs "dark current".

    Dark current goes up with temperature. However, dark current is also a function of lattice and surface defects in the pixel. Some pixels can have an order of magnitude or more dark current than normal pixels. So as exposure time and temperature goes up some pixels will be much more affected by dark current than others. Those with lattice or surface defects will look like a stuck pixel at long exposure even if they look normal at short exposures. That's what I meant by "hot pixel" - pixels with abnormally high dark current. This is distinct from "stuck pixels" which are read as saturated regardless of exposure time and are handled by the bad-pixel map in the camera. Besides those two kinds of defects there is of course non-uniformity in dark current in normal pixels that contributes significant shadow noise in long exposures and the dark frame subtraction with help reduce that significantly.

    And bottom line - yes all sensors have these effects at long exposure. It is unavoidable.

    Ken
     
  16. homerusan

    homerusan Mu-43 Regular

    130
    Dec 25, 2012
    izmir, TURKEY
    ok then is there an edge that every camera has or all cameras (cmos sensors especially) gives same amount of this pixels in the same conditions?
    if i use 5dm3 other than my e-pl2, in same conditions, are those pixel amount change?
    Thanks
     
  17. RobWatson

    RobWatson Mu-43 Hall of Famer

    Not sure I understand the question . Every sensor is unique in this respect. Take 10 Cannon 5DMarkIII and they will all be different in terms of the distribution of such pixels. Unless we can gain access to the actual sensor manufacturers sensor datasheet we cannot make less than overly broad generalizations about such things.

    It is true that one instance of a sensor may have really low dark current and a very uniform distribution in both intensity and pixel location these are few and far between. I used to receive cameras in batches of 35-50 a month and sort them based on exactly this distribution - the 'good' ones went into the high end product and the 'others' went into the lower end products.
     
  18. Cruzan80

    Cruzan80 Mu-43 All-Pro

    Aug 23, 2012
    Denver, Co
    Sean Rastsmith
    I think what he is asking is if any specific model of camera is known to have less issues with dark-current, or less pixels which are affected when shooting for long periods of time. I don't know of any specifically.
     
  19. RobWatson

    RobWatson Mu-43 Hall of Famer

    Yes, and without sensor datasheets or manufacturers stated specs we must fall back on crowd sourced empirical data sets in order to attempt an informed decision. I also don't know of any.

    If this is seriously the primary concern then purchasing a cooled camera is the most direct route to a solution. That opens a whole 'nother can o' worms ...

    I think it would be prudent to first use all the tools like noise reduction and pixel mapping, etc of the gear at hand before making a determination that the camera one already has is not suited to the task. Even cooled cameras need such treatments.
     
  20. RT_Panther

    RT_Panther Mu-43 Legend

    May 4, 2011
    Texas