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rea5245
Known Participant
May 10, 2018
Question

Selectively darkening night sky?

  • May 10, 2018
  • 3 replies
  • 1755 views

Hi,

I have a picture of a lighthouse at night, with a starry sky. The lighthouse is shining a red beam and you can see a cone of light stretching across the sky.

I want to darken the sky so that the space between the stars is blacker. Problem is, that darkens the red cone of light too, and lessens the distance it stretches. If I just darken the green and blue channels, the whole sky gets a red tint. Selecting the red cone and adjusting its brightness separately sounds like it would look fake, even with feathering.

Can anyone suggest an approach to isolating this cone of light and brightening it (or excluding it from darkening)?

Thank you,

  Bob

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    3 replies

    Norman Sanders
    Norman Sanders
    Legend
    May 10, 2018

    We would be better able to provide advice if we could see the image. You can post it here:

    That said, from your description, a first approach would be to look at individual channels to see whether one may have potential as the basis for a mask to be applied to a corrected area on a duplicate layer. That gives you an option from not three, but ten channels to consider. 

    Also, not to be overlooked is the possibility of a small increase in saturation of the cone of light rather than an adjustment of the tone value of the sky. One more reason for showing us the current image.

    R
    rea5245Author
    Known Participant
    May 10, 2018

    I'm sorry, but ten channels? What would those ten be?

    Here's the original shot:

    And here's what I've post-processed it to so far:

    The things I've gained in my processing include more stars, darker sky, more detail in the land, and some color in the ocean. What I've lost is the full extent of the cone of light and the dramatic red reflection in the water.

    - Bob

    JohanElzenga
    Community Expert
    JohanElzengaCommunity Expert
    Community Expert
    May 10, 2018

    I‘m a bit surprised about the bottom part of the image. Why didn’t you mask that out? There is no reason to brighten this part if you want to darken the sky to see more if the stars.

    -- Johan W. Elzenga
    Omar.Fathy
    Community Expert
    Omar.FathyCommunity Expert
    Community Expert
    May 10, 2018

    And you can also adjust your colors with Filters>Camera Raw Filter it will give you more options to adjust just whites,blacks,highlights and  shadows  or editing a specified area or colors.

    Note: Camera RAW Filter DOESN'T work with the CMYK color mode but it is working with RGB.

    JohanElzenga
    Community Expert
    JohanElzengaCommunity Expert
    Community Expert
    May 10, 2018

    There are several ways to approach this. The first way is to use an adjustment layer with a curve that bends down only in the left area (meaning you only darken pixels that are already quite dark). Another method would be a similar adjustment layer, but with a luminosity mask as well. You could also use Camera Raw as filter, and see how well a local adjustment with a range mask works.

    -- Johan W. Elzenga
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