NX/NX2:Gen - Commands - threshold vs highlight ??

Discussion in 'Nikon Capture and View NX' started by Allan, Jul 16, 2008.

  1. What is the difference in threshold (high end) and lost highlights? When I click the double threshold box I often get no highlights shown, but when I go to the menu and select show lost highlights, there are lost highlights.

    Below is a simple example. When I clicked the double threshold shot when I opened this plover image - the histogram section was entirely gray. However, when I selected show lost highlights - you see there are some. I don't understand the difference.

    332932363_fPqKw-L.

    332932398_jjhpu-L.
     
  2. Allan,

    My guess is that the double threshold doesn't record the lost highlights and shadows, only the darkest and lightest luminosity that is not lost. But I really don't know.

    I look forward to this discussion because rather than using the double threshold, I use lost highlights and shadows for determining the right and left end points, respectively, of my LCH editor sometimes in conjunction with Color Control Points to recover the lost extremes. That method, which I've never seen described, works great, as is demonstrated by both the histogram and the appearance of the image.
     
  3. Tosh

    Tosh

    May 6, 2005
    NY
    Allan,

    I always assumed that the colors you see on your posted Show Highlights screen represented partial clipping (i.e., not all channels are blown). White color represents blowing in all channels.
    My guess is than an image point needs to have clipping in all channels before it will show up on Double Threshold.
     
  4. Tom, I admit I am confused. Are you saying the lost highlights are o.k. to have as the r-g-b (combo) is only 241. What I have been doing in a situation like this image is as a first step reduce ec to gte rid of lost highlights. Is that good, or would you do something else if you wer trying to work with this image?
     
  5. Tom, I'm having a difficult time understanding the overall concept you're explaining, probably because I don't understand the following detail:

    I had understood that if it is a lost highlight, it is a tonal value to the right of 255. Similarly, if it is lost shadow, it is a tonal value to the left of zero. Is my understanding not correct?
     
  6. TomaS

    TomaS

    497
    Aug 3, 2006
    Corrales, NM
    My interpretation of the difference, which seems to be confirmed with a bit of experimentation. The histogram (and double threshold option) represents the TOTALITY of the data captured by the sensor. The 'lost highlights' and 'lost shadows' represent the data that cannot be displayed in the current color space. Change the color space, and the histogram remains the same, but the 'lost shadows' and 'lost highlights' display will change (depending on the image and color space selected).
     
    Last edited by a moderator: Jul 16, 2008
  7. Tomas, did you mean to write that they CAN be displayed or that they can NOT be displayed?
     
  8. TomaS

    TomaS

    497
    Aug 3, 2006
    Corrales, NM
    i mean CANNOT (silly me). I will update the post. :eek: 

    The important thing (if i am correct) is that the histogram and double threshold view are color space independent. I also believe that most (if not all) Color Space choice is more limited in what can be represented that what the sensor captures.
     
  9. That's very helpful, Tom. As usual!

    When people refer to the "clipped" highlights to the right of 255, what are they referring to?

    EDIT: I have been using Color Control Points to recover lost highlights and shadows by adjusting the brightness and/or saturation. Does that not have the same effect as any of the methods you described? (I haven't yet opened the picture and followed your precise instructions.)
     
  10. All of that makes sense, Tom.

    My take from this very informative discussion is that I need to adjust a few images using the two methods to determine if I can perceive different results using the double threshold as you describe as opposed to recovering the lost highlights and shadows as I described. Though recovering highlights and shadows as I describe result in degraded colors from a technical aspect, I wonder if the degradation is apparent purely by looking at the image as opposed to noticing changes in the histogram.

    I'll get back to you with the results, probably this weekend.

    Thanks again!
     
  11. Most of the time I use the little triangle at the top of the levels and curves or the LCH graphs to bring the highlights under control, instead of the ec.

    Nancy
     
  12. Tom, I have followed your precise instructions using the OP's image and now I understand your points. Thank you!

    However, I still come back to my method of using Shift-S and Shift-H in combination with the LCH Editor and I get the same results as using the double threshold. (It can be done using the Levels and Curves instead of the LCH Editor but I always use LCH.) The results are confirmed using the OP's image because the value at which the first lost shadow occurs is the same value as the darkest point in the double threshold. Similarly, the value at which the first lost highlight occurs is the same value as the lightest point in the double threshold.

    My method is shown below:

    1) Open the LCH Editor.
    2) Shift S (to view lost shadows)
    3) Move left slider to the right until a lost shadow barely begins to appear
    4) Shift H (to view lost highlights)
    5) Move right slider to the left until a lost highlight barely begins to appear
    6) Shift H (to toggle off the lost highlights and view the image)

    At that point I've got my left and right end points set at the exact same place as if I had instead used the double threshold and applied black and white points. My next step is to adjust the curve in between those points as desired. As I do that I check the lost highlights and shadows to ensure that my new curve hasn't created any new lost highlights or shadows.
     
  13. I have a very sore back so I am not spending much time at teh computer lately. However, I do not understand this thread as it pertains to the images I posted when I began the thread.
    Mike, on my images there were no lost shadows but blown highlights. In double threshold, the image was all gray, which I thought meant I could move the highlights in levels to the left.
    What do you think of my image - is it blown out in your opinion - even tough threhold doesn't indicate that?
     
  14. Allan, sorry to learn of your back problems. I hope they clear up soon.

    I think I was making some important edits to my most recent post as you were posting your message, so you might want to reread my post.

    Actually, I think you're working from an incorrect premise. It's possible to have an image that the lightest value is 240 and the darkest value is 20 and that lost shadows and/or highlights appear at values that are in between those two values. I think that's one of the points that Tom makes. That's why I always monitor the lost shadows and highlights after I adjust the curve, to ensure that my new curve didn't create lost shadows and highlights that appear in between the far left and right values.

    EDIT: My first response comes back to the point that I think you're using an incorrect premise. The double threshold at the point that it is first opened isn't attempting to indicate whether there are any lost highlights. Instead, it's only indicating whether there are any in the 255 value. Now that I understand Tom's point that lost highlights appear at lower values, that's exactly why I will continue to look for lost highlights and shadows so rigorously throughout my post-processing workflow.

    To directly answer your question, when I view your image at 150%, there seems to be no detail in the area where lost highlights are indicated. That indicates that the highlights are blown. However, it's really hard to tell because the Internet image is so small and because the portion of the image that is showing lost highlights is also so small.

    Your best bet is to look at your original file that came out of the camera at 100% in the area that lost highlights are indicated. If you can't see any detail in that area, the highlights are probably blown.
     
    Last edited by a moderator: Jul 19, 2008
  15. Tosh

    Tosh

    May 6, 2005
    NY
    In real life, the human eye naturally sees "blown highlights."
    Glare, reflection, etc. are part of our visual field.
    While we should be concerned generally with blown highlights in order to retain as much detail as possible, if we get too obsessed with it our images will appear unnatural. JMHO

    I think Allan's shot is fine as is.
     
  16. I should have made that point, Glenn. Thanks for mentioning it.

    My assumption all along has been only that his image is being used as an example for discussing the similarities and differences between using Capture NX's double threshold and the lost shadows and highlights.
     
  17. Tom, that's a really nice treatment of that particular image. I know you have mentioned that method in the past, but I look forward to you doing a tutorial about it very soon. :biggrin:
     
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