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Highlight Recovery - HDR vs. Levels and Curves

Denis Mortell
Sometimes, when I move the Highlight slider all the way to the right, I don't achieve total highlight recovery.

However, if I then drag the top of the Levels Highlight slider to the left, or drag the top right hand corner of the Curves line down (either just a couple of clicks of the minus key) I appear to recover the remaining, missing highlight area.

Or am I?

What is happening when I do this?

Am I losing anything?

Thanks.

D.
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Comments

8 comments

Date Votes
  • Ian Wilson
    Moderator
    Top Commenter
    I'm not convinced that moving the levels top slider in actually recovers highlights. It just maps the level of 255 to say 248. If your highlight is 255 down out, doesn't it just convert it to 248 blown out? I don't much use them, but I think that the main use of the top sliders is to fit in with the requirements of printers who may sometimes prefer your blacks, say, to be just a couple of points away from our black, etc.

    I think that the first thing you can do is try reducing the exposure slider a long way (temporarily). Sometimes that blown out highlight (such as a patch of sunlight) remains blown out however much you reduce it, in which case you know there is not a lot you can do, but it's interesting to try it to see what happens. Having put the exposure back to where you started then, depending on the result of what you just tried, you could consider reducing exposure a little, and then you have a bit more leeway on the highlight slider.

    Or you can get more than 100 highlight recovery like this. Pull the highlight slider all the way up to 100. If that is not enough, create an adjustment layer. Click on the little ... symbol and choose invert mask which will quickly give you a mask covering the whole image. Then for the adjustment layer, pull the highlight slider up again. If you pull it to 50, you are effectively getting 150 in total.

    Ian
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  • Denis Mortell
    [quote="Ian3" wrote:
    I'm not convinced that moving the levels top slider in actually recovers highlights. It just maps the level of 255 to say 248.

    I thought the same myself.

    Or you can get more than 100 highlight recovery like this. Pull the highlight slider all the way up to 100. If that is not enough, create an adjustment layer. Click on the little ... symbol and choose invert mask which will quickly give you a mask covering the whole image. Then for the adjustment layer, pull the highlight slider up again. If you pull it to 50, you are effectively getting 150 in total.

    That's interesting. Though I'm not sure if what I'm seeing is any better than what I described above.



    Thanks for the reply.

    D.
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  • Denis Mortell
    Ps.

    If, in moving the slider to the left to say, 250, you are simply changing the level at which clipping occurs, which is what you seem to be implying;

    1. Why does the over all image darken when I do this?

    2. Why do the remaining clipped areas (shown in red on the image) lose their highlight warning and become visible and textured?

    3. If I'm reducing the number at which clipping occurs (by, say, moving the slider to 250) then shouldn't I be seeing more red in my image and not less?

    Or am I seeing things! 😎

    Thanks.

    D.
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  • HansB
    Reducing the maximum level in 'Levels' or 'Curves' reduces the dynamic range of the image. It does not recover more highlights. And it means bringing clean white down to a bright gray. A no-go for high quality printing.
    Because of the math behind it, it can even lower the efficiency of the recovery tool. (Not going into details here.)
    It may still look like better recovery, but that heavily depends on the monitor, it's brightness setting, and it's profile.

    Two examples I'm using it for:
    1) Creating non-distracting background images.
    2) Exposing for maximum dynamic range. In a set where the brightest spot is, lets say, mid gray, exposure will make it bright gray, close to white. I bring it back down using the top level or curve's top end, because the exposure- and brightness sliders cannot do this job. (Exposure shifts dark image content into solid black, brightness keeps bright gray as bright gray.)


    Regards,
    Hans
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  • HansB
    Using the highlight line in 'Levels' tool, pulling the lower handle to the left means clipping everything above to solid 255 (or whatever the upper handle is set to). Any existing overexposure warning will grow.
    Pulling the upper handle to the left compresses the brightness of the image into the dynamic range you defined. The image becomes darker. Any existing overexposure warning decreases, but just because brightness no longer reaches the warning level.


    Regards,
    Hans
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  • Denis Mortell
    [quote="HansB" wrote:

    2) Exposing for maximum dynamic range. In a set where the brightest spot is, lets say, mid gray, exposure will make it bright gray, close to white. I bring it back down using the top level or curve's top end, because the exposure- and brightness sliders cannot do this job. (Exposure shifts dark image content into solid black, brightness keeps bright gray as bright gray.)


    Regards,
    Hans


    Excellent reply and very useful to know.

    Many thanks.

    D.
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  • Denis Mortell
    Ps.

    Hans,

    Does this bit of Ian's reply make sense to you?

    "Or you can get more than 100 highlight recovery like this. Pull the highlight slider all the way up to 100. If that is not enough, create an adjustment layer. Click on the little ... symbol and choose invert mask which will quickly give you a mask covering the whole image. Then for the adjustment layer, pull the highlight slider up again. If you pull it to 50, you are effectively getting 150 in total."

    Thanks.

    D.
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  • HansB
    Trust him. He's right. 😄
    Just follow the steps in his instructions.

    You can repeat it over several layers, if it is useful for the look you want to achieve.


    And
    [quote="Dinarius" wrote:
    [quote="HansB" wrote:

    2) Exposing for maximum dynamic range. In a set where the brightest spot is, lets say, mid gray, exposure will make it bright gray, close to white. I bring it back down using the top level or curve's top end, because the exposure- and brightness sliders cannot do this job. (Exposure shifts dark image content into solid black, brightness keeps bright gray as bright gray.)


    Regards,
    Hans


    Excellent reply and very useful to know.

    Many thanks.

    D.

    glad you found it useful.


    Regards,
    Hans
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