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PSD
Joined: 12 Oct 2009
Posts: 3
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 Posted: Mon Oct 12, 2009 4:52 pm Post subject: Help Selecting Lightness Range |
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I want to create selections which will target pixels based on their lightness values. This seems like it should be a simple task but I'm plain stumped.
My goal is to create an action that will assign lightness-based Layer Masks (that only target specific ranges and exclude all others) to Hue/Sat Adjustment Layers for awesome color control.
Specifically, I'm trying to select these ranges:
Highlights: Only pixels with lightness values between 1% and 14%.
Lights: Only pixels with lightness values between 15% and 28%.
Light Mids: Only pixels with lightness values between 29% and 42%.
Midtones: Only pixels with lightness values between 43% and 58%.
Dark Mids: Only pixels with lightness values between 59% and 72%.
Darks: Only pixels with lightness values between 73% and 86%.
Shadows: Only pixels with lightness values between 87% and 100%.
Does anyone have some ideas?
I developed the idea based on the HSL and Tone Curve controls in Camera Raw. In theory, this will allow for better color control than anything currently available in Photoshop or Camera Raw. I would love to make this action available for free online as well as use it in my own workflow! |
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hawkeye
Joined: 14 May 2009
Posts: 2377
Location: Mesa, Az
OS: Windows 7 Pro 64 bit
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| Posted: Tue Oct 13, 2009 12:11 pm Post subject: |
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The closest thing I can think of for what you want to do is luminence masking. Way too complex to discuss here, Google for it. |
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Matt
VIP
Joined: 24 Sep 2007
Posts: 3515
Location: Haverhill, UK
PS Version: Lightroom 5, CS4 & Elements 11
OS: Windows 8.1
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| Posted: Tue Oct 13, 2009 2:46 pm Post subject: |
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PSD
Joined: 12 Oct 2009
Posts: 3
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| Posted: Wed Oct 14, 2009 3:33 pm Post subject: |
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Just the standard histogram in Photoshop. I found a solution in a different forum, and it happens to be completely non-complex and intuitive. It turns out there are plenty of ways to accomplish this "smart luminance mask" technique, but the one I will describe has every advantage:
It's completely straightforward, uses minimal steps, you can see the selection preview on the fly, there is a "Smooth" button to help with transitions, and all it relies on a single adjustment layer that can be repeatedly modified (or turned off). Nothing arcane or complex involved.
1. Start with a black and white version of the image (using your favorite method).
2. Create a curves layer adjustment. Make sure the "Show Amount of:" option is set to "Light (0-255)" instead of "Pigment/Ink %". Also make sure you are using the curves pencil tool instead of using points.
3. Draw a line across the bottom to set the lightness output value for all pixels to 0. Draw a line at the top (output of 255) within the input range of pixels you want to turn white (white = selection). Hit smooth once or twice if you prefer smooth transitions, and press OK to accept the curve.
4. Press Ctrl+Alt+2 or Cmd+Opt+2 to select your range. Add an adjustment layer of your choice, it will automatically have the mask assigned to it by virtue of the fact that you had a selection active when you created it. You can now turn off or delete the curves layer, or you can continue to modify it for further selections.
The result is a "smart" luminance mask, as opposed to the standard luminance masked talked about everywhere which is completely arbitrary and results from simply selecting a channel.
Easy as pie. If it looks complex that's because I tried to add details for newer users. I hope people find this helpful. |
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Matt
VIP
Joined: 24 Sep 2007
Posts: 3515
Location: Haverhill, UK
PS Version: Lightroom 5, CS4 & Elements 11
OS: Windows 8.1
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| Posted: Thu Oct 15, 2009 11:03 am Post subject: |
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Nice technique PSD. I guess working with a greyscale image means it's just as effective to work with an RGB histogram as it would be to work with a luminance version.
A smart luminance mask, I like it. Thanks for taking us through the steps too!
_________________
Matt
3photoshop.com
http://www.3photoshop.com |
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PSD
Joined: 12 Oct 2009
Posts: 3
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| Posted: Thu Oct 15, 2009 10:05 pm Post subject: |
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You're welcome 
I swear it's impossible to find this information on google, the only results are standard luminance masks -- but that has changed now. Thank god for forums.
Creating the luminance mask from a grayscale composite helps with the selection. The grayscale can be discarded or turned off (in other words, the image can be reverted to a color composite) after the mask has been achieved. Of course the mask is equally applicable to grayscale images so it wouldn't hurt at all to just use it there instead. |
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Matt
VIP
Joined: 24 Sep 2007
Posts: 3515
Location: Haverhill, UK
PS Version: Lightroom 5, CS4 & Elements 11
OS: Windows 8.1
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| Posted: Fri Oct 16, 2009 5:01 am Post subject: |
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Yeah you're right, can't see any reason why it wouldn't work on either a colour or greyscale image. Nice work!
_________________
Matt
3photoshop.com
http://www.3photoshop.com |
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