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Hot corners on dark images

Discussion in 'GFX 50S' started by SOLDATI, Dec 5, 2017.

  1. SOLDATI

    SOLDATI New Member

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    On dark images of 1” @ 12800 ISO, I have two hot areas in the left corners of the image. This is even more pronounced when the electronic shutter is used. No noise reduction applied.

    Do you have similar results or my sensor has a problem?

    [​IMG]
     
    Last edited by a moderator: Dec 5, 2017
  2. PatrickP

    PatrickP Premium Member

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    I do not see anything weird in the frame above.

    But 1 second @12800. Did you expect a totally clean image?
     
  3. jamescp

    jamescp Premium Member

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    +1
     
  4. bobbyzfx

    bobbyzfx Premium Member

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    Don't see anything.
     
  5. Shadowside

    Shadowside Good Glass is Forever...

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    I don't see anything either...

    So, how's that monitor workin for ya?
     
  6. Tom239

    Tom239 Premium Member

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    Not that I'm seeing especially light corners either, but--
    did you let the camera convert to .jpg? If so, it may be
    lightening the corners to correct for lens vignetting.
     
  7. Macro

    Macro Premium Member

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    Top-left and bottom-left corners are visibly lighter in your posted image.

    More visible after a quick levels adjustment.

    Image 235.png
     
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  8. SOLDATI

    SOLDATI New Member

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    Thank you Marco for the level adjustment. This reveals the lightening problem. More visible in the left corners but there is also a gradient from left to right. I will post an actual image to give you an idea in real life.
     
  9. SOLDATI

    SOLDATI New Member

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    [​IMG]

    [​IMG]
    Crop of the bottom left corner

    Due to the rapid changes in this Aurora with Nitrogen fringe, I wanted to shoot relatively fast. This is a 2s exposure @ 3200 ISO @ f/2.8. The picture as shown has been pushed less than one stop (0.72).

    In comparison, the footages taken the same night with the Sony A7s taken at 2000 ISO are absolutely clean even if I push 4 stops an underexposed picture.
     
  10. SOLDATI

    SOLDATI New Member

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    Would someone be so kind to take a 1sec. exposure with his camera at any ISO from 3200 and above (long exposure NR off) with the cap on the lens and see if there is the presence of the hot corners.

    This will be very helpful to determine if it is a known behavior or if my camera needs to be fixed.

    Thank you very much for your help!
     
  11. bobbyzfx

    bobbyzfx Premium Member

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    I can check over the weekend. Someone I know from work does like 30mins shots with his GFX. Maybe check with him as he is more experienced than me.
     
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  12. jknights

    jknights Moderator Staff Member

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    Not a big diference but I wouldnt expect to see it on a flagship camera.

    Possibilities are:
    Light leak like on the early XT1 cameras?
    Some light reflection into the lens but it looks too specific?
    Some other problem?
     
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  13. SOLDATI

    SOLDATI New Member

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    That would be great. Thank you very much for your help. It is very appreciated!
     
  14. SOLDATI

    SOLDATI New Member

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    Thank you for your input. I totally agree. I wouldn’t expect to see it on this kind of camera. For example, the darks are clean on the Sony a7s.

    To me it looks like to be electrical noise. It is more apparent when shooting with the electronic shutter (ES) than with the mechanical (MS).
     
  15. SOLDATI

    SOLDATI New Member

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    VERY QUICK TEST :

    Set your camera at ISO 12800, shutter speed of 1sec., electronic shutter (ES).

    Take a picture and look the result directly on the screen of your camera.

    On my copy, I have hot corners on the right (mostly bottom right) with a gradient from left to right.

    Do you have the same?
     
  16. PatrickP

    PatrickP Premium Member

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    Why electronic shutter? That is asking a bit for these kind of issues....
     
  17. lawsofphysics

    lawsofphysics Premium Member

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    This is absolutely normal when no signal is present.

    Every digital camera in existence appears flawed when there is no signal from light in the data.

    In fact, under these circumstances, the analog noise and artifacts become the signal. The noise and artifacts are always present. But when signal (light) is present, they are below the analog-to-digital converter's minimum DC voltage detection threshold. They aren't digitized.

    In rare circumstances (extraordinary low light levels) these sensor artifacts become important.
     
  18. SOLDATI

    SOLDATI New Member

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    Good question! For the test purpose using the electronic shutter gives you the assurance that no dark substruction is applied to the image (long exposure NR off).

    Dark substruction can correct the hot arias but, if I am not mistaking, it is not applied in images less than 1sec. exposure, even with long exposure NR on.
     

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