NX - white and black control point question

Discussion in 'Nikon Capture and View NX' started by Allan, Jun 16, 2007.

  1. I have seen many tutorials on NX, the latest being Vincent Versace's. In them they deal a lot with landscape examples; I shoot birds.

    My questions has to do with white and black control points. I can't see why I would want to use them - but in all tutorials they do???

    I took an image of a gbh in a tree. I open it up in NX and click the double threshold box. There are some black areas and no white areas. I move the right slider to 253 and see 1 tiny area of white.

    When I select the black and white control points in that area, I get much more black and white areas. Why would I want to do that?

    Are there others who just ignore b and w points?
     
  2. Alan,

    The next time you do that, go ahead afterwards and uncheck the double threshold. Then open up the curves box and just click on "Auto Contrast". If you chose the correct black and white control points, you will see your contrast doesn't change..........it's pretty much "on the spot". Then go back clear it out and start over and this time ignore the double threshold box and do the Auto Contrast and you will see it usually makes a change in your contrast. The double threshold doesn't seem to add highlight blocking, or blocking of shadow detail................it just enhances both. At least that's the way it seems to me.
     
  3. But why do the control points. I always used double threshold and move ev, then slides os there is few black and white points showing. But when I use b^w control points there are more black and white points showing (with double threshold checked.) Doesn't that mean you are increasing the blown highlights and blocked shadows?

    Or am I missing something?
     
  4. Not certain I can answer you question there. I'm a total newbie to NX....though I love it so far. Why don't you e-mail Jason. He's been very helpful when I've contacted him.
     
  5. I don't know Jason. Which of the Jason's here do you mean?
     
  6. Sorry........................Jason Odell, who wrote the e-book The Photographer's Guide to Capture NX. He's a member of this forum.
     
  7. HSNewman

    HSNewman

    173
    Aug 17, 2006
    Maryland
    I've been using the black and white control points from palette F4 with good success on most but not all pictures. As mentioned, I first adjust exposure compensation by clicking double threshold in the histogram window and moving the compensation slider (up or down) in Raw Adjustments until all white points just disappear (occasionally I'll ignore a small blown spot).I then adjust the histogram sliders so black and white points just appear. After clicking on the palette 4 black point control, I move the cursor over the black while looking at the the watch point numbers. I click when I find a minimum, hopefull in the 10s or 20s. I then set the rbg channels in the black point dialog box to 10,10,10 to set the black point. I repeat with the white point setting the RGB channels to 250 each. I find that this process both matches the picture's (dynamic) range to display's (dynamic) range and removes any color cast left over from white balance mismatches. It also works on JPGs converted to NEFs where white balance is not available. I'd be interested in hearing comments on the process.
     
  8. Thanks for the answers. I still don't know a procedure I will use. But:

    1. I did write to Jason. He said he doesn't use them. He stops when moving the sliders shows black and white.
    2. A good friend who shoots landscape uses them all the time. However, his shots usually show all gray when he checks double threshold. Mine usually show some black, which is o.k. with me as I shoot birds and the black in not part of the bird.
     
  9. Allan,

    If this will help you more, this is what I do:

    I move the sliders to points where they show just enough of both the black and white to place control points on them. Then when I un-check the box to see the resultant image, I sometimes find there isn't quite enough detail in the black, or maybe I've blown the highlights. I click on the appropriate control points and make very minor adjustments with the sliders. (I've found I can definately go too far with this step!) If I took perfectly exposed images I wouldn't have to do more than adjust the original sliders..........but I don't!:biggrin:
     
  10. Thanks Chris. I have been trying something like that over the weekend. I move the sliders looking for black and white pixels to show. I might back off on the white if it is an important to have some detail there.

    Do you ever just stop there? I still wonder the usefulness of the cb&w points, at least on the bird shots I take.
     
  11. Allan,

    The reason I go ahead and set the control points is that then I can view the image while I change the amounts. If you just use the sliders on the double threshold, you can't really see what is happening. So, in answer to your question..............no, I don't stop there. Sometimes I don't need to do anything, but I usually find I want to tweak one or the other very often.
     
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