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Thread: low light artefacts

  1. #1
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    low light artefacts

    hello!

    on CFV16 + 500cm:

    I am experimenting these vertical lines in low light, they show when I raise shadows in Lightroom, anybody experimented this before ? is that a normal issue with CFV16 ?

    thanks!

    https://lh6.googleusercontent.com/-M...of+74%2529.jpg

    https://lh3.googleusercontent.com/-t...of+74%2529.jpg

  2. #2
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    Re: low light artefacts

    I think these backs have some line noise if pushed hard. Are the images underexposed, and pushed in lightroom a lot?

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    Re: low light artefacts

    yes! pushed in LR a lot, don't have any of these artefacts with good exposition...

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    Re: low light artefacts

    Phocus will always produce a better result than LR, particularly with underexposed images.
    Cheers,
    Jeff
    www.jeff-grant.com

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    Re: low light artefacts

    imho, perfectly normal if pushed hard!

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    Re: low light artefacts

    Nik DFine 2 (now from Google) has a "debanding" filter that should work very well on this type of noise. Be sure to choose "vertical" banding in the filter.

    It also works wonders on high ISO underexposed files from the Leica M240.
    Brad Husick
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    Re: low light artefacts

    Ok!!thanks guys for the advice

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    Senior Member ondebanks's Avatar
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    Re: low light artefacts

    Quote Originally Posted by elrafo View Post
    hello!

    on CFV16 + 500cm:

    I am experimenting these vertical lines in low light, they show when I raise shadows in Lightroom, anybody experimented this before ? is that a normal issue with CFV16 ?

    thanks!

    https://lh6.googleusercontent.com/-M...of+74%2529.jpg

    https://lh3.googleusercontent.com/-t...of+74%2529.jpg
    Did you rotate the first image by a few degrees in Lightroom? I ask because the banding is not vertical, whereas it seems to be exactly vertical in the second image.

    I have the same sensor in a different back, but I have never seen anything like that degree of banding. If I take what is effectively a bias frame (camera at fastest shutter speed, lens capped, smallest aperture or darkened room just to be sure no light gets in), shot at ISO 400, and push it to the equivalent of ISO 1600, only then do I start to see very subtle, broken wavey bands. I've seen this behaviour before in several CCDs, including highly tuned astronomical CCDs. It disappears though if I set the back to subtract a dark frame of equal time, which tells me that the subtle pattern is repeatable. That's the key thing - being repeatable means that it can be cancelled out.

    Could you take a couple of bias frames, separated in time, and show them here? That would remove the variable of external light and we could see what the readout process alone is doing, and how repeatable the pattern is. Subtracting an internal dark frame would be another key test, but I don't believe your CFV16 back can do that?

    Ray

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    Re: low light artefacts

    Without wishing to flog a dead horse, it is my understanding that Phocus will always do a better job than LR with images like this.Why not use Phocus to get the basics right, or has hammering nails with spaghetti become fashionable?
    Last edited by Jeffg53; 24th April 2014 at 20:19.
    Cheers,
    Jeff
    www.jeff-grant.com

  10. #10
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    Re: low light artefacts

    CFV16 is not designed for shots like this. you'll get much better results in doors from a any modern day prosumer camera.

    safe the CFV16 for those outdoor shots

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