For Ron; question about type of image

Discussion in 'General Technical Discussion' started by Rich Gibson, Mar 25, 2005.

  1. Ron (or anyone knowing the answer)

    I have a bunch of images in which the bright sky plays a prominent part. Thus I get a histogram which looks like a ski slope with the high end toward white. The book deals with little, low or no light. These images are the opposite. The problem is whatever shadows there are hard to find, lett alone the gamma points.

    Like this for example. Sorry I can't post the NEF.

    original.

    Anyone, how do you approach this in N.C. using the RR postprocessing model? (Dingle harbor, Ireland May 2004)

    Thank you in advance.

    Rich
     
  2. Hi Rich

    I guess it depends on what your objective is. If you want to tone down the sky without impacting on the foreground, then I suggest you do it in photoshop, using a second layer and a layer mask. Tone down the sky using curves and paint in the sky or the ground, depending on how you have executed the mask.

    In other converters, such as RSE and Bibble, they give you more control over the highlights than capture, and you can do more, but not as well as layer masks in my opinion.
     
  3. Well, no I was writing in general about sky heavy (bright, where the histogram is mostly on the right) images. I also have overcast images where there is no definition at all and ones in which the sky is a bright blue. I can't seem to figure out how to do the shadow (gamma) work using Ron's technique.

    Thanks, Rich
     
  4. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Let's first determine where the spike is. 225 on composite histogram in PS, middle of quartertone. Now in composite curve we can tone this down by 10, to 215. Thus we also are giving a little more space to highlights, improving gradation and enhancing contrast, as now highlight portion of the curve is steeper.

    Now let's protect shadows and midtones. To do so, we are interested in small hump on the right slope of the second hill. Why? Because it is reflection on the water. We do not want it to go dull. 178. We fix this point on the curve, and bring it back to straight translation 178 -> 178. Adding a couple more points past this one (to shadows) to straighten the curve.

    Next interesting point is 121 - very small spike on the plato of the third hill. We can also add some point in shadows between 25 and 70, where we have dull horizontal histogram.

    Finally, Fade to Luminosity.
     
  5. Thank you Illiah! Talk about taking a "sip" from a fire hydrant! :? There's a lot to dig into; I really appreciate your analysis. It's going to take me a while but I know it's worth it. The trouble is I'm probably going to come back with more questions.

    Rich :D
     
  6. Thanks Frank.
    Rich
     
  7. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Frank,

    Levels are very crude adgjustments. The math behind levels introduce much more noise and posterization then curves. Levels are taboo in serious postprocessing, same as contrast and brightness. Basically, levels are curves with 5 control points, but this points are placed so that they do not allow control over most inportant zones - 3/4 and 1/4 tones. Besides, computations used in Levels seems to be much more prone to rouding errors then computations used in curves.

    Before going to adjustments using local masks, it is better to make the best global adjustment possible.

    Rich,

    We definetly can find some common language in that game of Q&A :)
     
  8. Iliah, when you say "tone this down by 10, what do you mean. Are you talking about grabbing the curve at that point and dragging it downward?
     
  9. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Gordon,

    You are right, but - not grabbing. I add an arbitrary point, then go by Tab key to the numbers below curve dialog, and enter numbers. When I need to adjust the position of the point, I use Ctrl-Tab to navigate to that point, and arrows/Shift-arrows to adjust it. Mouse is too precious - I keep it on the image to watch numbers in Info palette.

    As you most probably know, points on curves are added by Ctrl-click and Shift-Ctrl-click on the image.
     
  10. Thanks Iliah and no I didn't know but now I do. :D :D
     
  11. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    That is very imporrtant feature - it allows to add to the curves exactly the points that precisely match the region we want to adjust. We keep eyedropper at 1x1, and to average region we go Ctrl-"-" up to 10%. Eyedropper picks approx 3x3 in this mode (square root of 100/10)

    The other thing is that we mostly use middle of the region for large concave adjustments, and start of the region while fixing the points for the regions we want to exclude from adjustments.
     
  12. I will go practice Iliah. I am always pleased to learn new things. Thanks again.
     
  13. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    My pleasure, Gordon :)
     
  14. Frank,
    Can you elaborate , step by step. Thanks
     
  15. F15Todd

    F15Todd

    Feb 1, 2005
    Tennessee
    True curves command gives you everything that levels command does, but I would not go so far as to say it's taboo in serious post-processing. You may not use it in your post, but many do, and get great results.
     
  16. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Todd,

    If you make a gradient (say, black to white, 512 pixels long, and add a yeydropper point to the info palette at X=255), set a Levels adjustment layer, and perform adjustment with gamma slider, sertting it to something les then 1; then make that layer invisible, and perform similar adjustments with Curves layer, how shadows compression compare? So, if we adjust in Levels for midtone, what happens to shadows? My results are

    http://www.pochtar.com/Crvs_vs_Lvls-MidtoneAdj.psd
     
  17. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Frank,

    My point is not the degree of control, but quality of levels adjustments vs. curves adjustments.

    I watched this discussion some years ago and decided to check myself.

    I have one Kelby book, but I prefer more methodical approach Margulis suggests.

    Re the image: it seems to me I see some of the Levels side effects on it.
     
  18. Jono Slack

    Jono Slack Guest

    A completely different approach

    Hi Rich
    I seem to come across weather like this all the time - All the help from Iliah is invaluable (and much better than I could have given). But I have another idea which you could try.
    Process the NEF file twice in your favorite converter - once with correct exposure for the sky secondly with correct exposure for the ground. Simply paste one into the other in photoshop, and erase the unwanted part on the top layer - this is simple and quick, and works very well.
     
  19. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Hi Jono, I think I described one of the methods to make HDR images about a couple of years ago :) Quoting myself (am I showing off? - No, just lazy to re-type the post) ):

    To recover highlights and preserve shadows sometimes this method helps:

    - make 2 tiff files from NC - one with exposure correction for highlights, and one - for shadows/mid-tones - usually about 1.5 stops difference in Advanced RAW;

    - bring them to Photoshop as 8 bit for PS7, or 16 for CS;

    - hit Ctrl-Alt-~ on the lighter image, you will have luminosity selection to be used for Luma mask;

    - shift-drag the background of darker image over the lighter, pressing Shift key before starting to drag is needed to adjust the new layer to the center;

    - hit "Layer Mask" at the bottom of "Layers" palette, you will have Luma mask on the darker image layer, so that it would affect the whole image mostly at white parts of the mask;

    Alt-click the mask to select it and add Gaussian blur (about 10 to 20 pixels for each 1000 pixels in longer dimension of the image), or median, if you need additional sharpness, or combine blur/median - this needs to experiment with, using History;

    - hit the background at the "Layers" palette, judge the results, possibly undo and set different parameters for blur/median. Than adjust with Curves/Levels/whatever.

    This is not something similar to Curves on the image in PS, as Advanced RAW adjustments affect RAW rendering.

    And of course, the luminosity mask can be additionally processed by painting on it, as you rightfully suggested.

    Thank you for kind words, but you are exaggerating way too much, and I feel very uneasy.
     
  20. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    Dear Frank, you misunderstood the message. It has nothing to do with you, instead it was an attempt to explain why I suggest another method. Crude has a very particular meaning in math - and if you search, you will find out that even PS Team suggested that Levels are a crude method.

    I have no intent to fight with you, or anybody else. I also have no intent to "belittle" anybody, anywhere.

    If you do not appreciate my attempts, feel free to ban me.

    If you do not appreciate my style, feel free to edit me.
     
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