Exposing For Best Color At Higher ISO

Discussion in 'Beyond the Basics' started by smoke665, Sep 27, 2017.

  1. smoke665

    smoke665 TPF Supporters Supporting Member

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    I read a comment in another post on this subject but now I can't find the thread. So apology given in advance for the question.

    What is your preferred exposure to get the best color, least chromatic noise in the shadows at ISO's of 12800 or above.
    • Do you expose right? Or expose for the shadows?
    • Use the highest shutter speed possible to seek to minimize stray light?
    • Is it possible for light leakage through the view finder, such as on a long exposure?
    I've reached a plateau where it seems that changes I've made aren't translating into better images. It may well be I've maxed out the camera capability.. Any comments on the subject.


     
  2. TCampbell

    TCampbell Been spending a lot of time on here!

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    I think you're talking about "noise".

    When you take a photo, your sensor captures "signal" (real information that arrived in the form of light) and "noise" (which is not real signal). Noise can be caused by lots of things (including quantum effects). The reason you generally see it at high ISO and don't at lower ISO isn't because low ISO doesn't have any noise... but rather because the noise hasn't been amplified or multiplied by camera processes.

    When you crank up the ISO (especially to levels such as 12,800 or above) the camera isn't actually capturing any more light... it's simply applying an amplification or multiplication to what it has on the sensor and this increasing everything ... including the noise and making it more noticeable.

    So the real answer is... how do you get rid of noise?

    De-noising techniques help reduce noise but they generally do so by averaging the value of a pixel with it's surrounding pixels and that naturally also causes a sharpening effect (e.g. if I have a detailed view of someone's eye-lashes and I average all the pixels, the eyelashes will lose contrast and not be as sharp.)

    This is usually a big problem when you use aggressive amounts of de-noising AND you de-noise globally. But you don't have to de-noise globally. Typically you want to preserve sharp details where the image has high contrast (such as edges or complex patterns, etc.) Where an image doesn't have much contrast (flat spaces where the image lacks strong contrast) is where you'll probably really notice the noise.

    So you can create masks or "paint on" your noise reduction to reduce noise in areas where you see it while preserving detail in areas that require the detail and noise isn't as noticeable.

    There are also third party noise-reduction tools (Nik Dfine2 is free and I use a paid program called Noiseware Pro) which are a bit more intelligent about noise reduction (you can tune them to be more aggressive in shadows, less aggressive in highlights, etc. or go after more "chroma" noise and less "luma" noise (or vice versa) for example.)
     
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  3. smoke665

    smoke665 TPF Supporters Supporting Member

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    Yes, primarily "chroma". Luma I can deal with.

    I think I've already got a decent understanding on selectively applying noise reduction in LR an PS with masks. I have the Nil collection but truthfully haven't looked at Define2. Need to open it up and explore it further.

    As to in camera, anything I might be missing on exposing differently for high ISO?
     

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