ACR curve for D2X

Discussion in 'General Technical Discussion' started by Iliah, Sep 27, 2005.

  1. Iliah

    Iliah

    Jan 29, 2005
    nowhere
  2. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    Interesting. Applying this curve to a couple of test images my initial impression is that it gives a boost to shadow details, and also lowers the overall apparent contrast of the images. I say "apparent" because I'm just describing my subjective impression of the image.

    Can you share what your thinking behind this curve is and whether it's designed for specific situations or general use? Also, if I want more contrast than this curve gives me should I

    a) Increase contrast and/or shadows sliders on Adjust tab.
    b) Use Curves adjustment in PS
    c) Use another ACR curve

    Thanks,
     
  3. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Jeff,

    The curve brings known target densities to their aim values. I prefer converters to provide me with some standard development, that is known reproduction of colour and density values. ACR has limited info readings, so I prefer to choose the "paper contrast" later in Photoshop.

    Two tradeoffs were made in regards to the curve: shadow push was limited not to increase noise levels past the values I can tolerate, and extreme highlights were left where they were to allow "highlight recovery" to work.

    Overall, it seems to me that the curve allows better dynamic range.

    Still, if you want more contrast right out of ACR, contrast slider is the second best way IMHO. First is to make a different curve.
     
  4. JeffKohn

    JeffKohn

    Apr 21, 2005
    Houston, TX
    Thanks for the explanation. I've saved the curve as one of my presets and will continue to evaluate it. I think I may also create a "weaker" version of it to see how I like that. I agree that for some shots it looks like it will give you more DR, however it also looks like for other types of shots it takes away some depth because the shadow boost is a bit too much for my tastes.

    I've been going through a bunch of concert shots I took weekend before last, mostly shot at ISO 800 or ISO 1600 and in those images the curve does seem to increase the noise.
     
  5. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Right, Jeff - I made it up to 640, or maybe you will tolerate less. But I'm mostly concerned with prints, where it works to 640.

    I'm pretty accustomed to low contrast negatives, and always develop my slides lower in contrast - boosting contrast is easy, and you can choose the range where you feel like doing that. Transposing the contrast from one tonal range to another seems more difficult to me, and more destructive.
     
  6. TOF guy

    TOF guy

    208
    Mar 11, 2005
    Thanks, Iliah very informative.

    I see that you're using the ColorChecker DC, but you only need a few patches for your picture (the pic shows only the squares near the large center white patch). If you have the chance please consider taking the same picture with a ColorChecker (the one with 24 patches). I'd be most grateful, as this is what I have. I could then try to reproduce the calibration with my own D70.

    In any case, thank you again for the post.

    Thierry
     
  7. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Thierry,

    The big advantage of DC is that the squares are grouped tightly, minimizing light inconsistency. Having stabilized studio lights and diffusers, I can shoot CC24. But the best thing to do is to get Q13, to slice it into 5 groups of 4 strips each, slice each group horizontally to make dimensions even smaller, and to fix on a cardboard, making a small rectangle, which is easy to lit evenly - all you need for that is a flash with a diffuser.
     
  8. TOF guy

    TOF guy

    208
    Mar 11, 2005
    I have a Kodak Q60. Would this work ? It * is * small.

    Thierry
     
  9. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Thierry,

    Q60 is not neutral, and exhibits metamerism.
     
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