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how can i separate colors from light ?

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  #11  
Old 08-08-2011, 11:32 AM
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mantra mantra is offline
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Re: how can i separate colors from light ?

Quote:
Originally Posted by assortedpixels View Post
I learned this method to replicate channels in PS Elements, but it may also help with what you're after.

The idea is to create 3 new layers one each of Red, Blue, Green. You can then use normal masks / selections techniques to modify only one color as desired.

To separate the colors.
1. Copy the background layer and leave it active
2. Create a new Fill layer (solid color), choose the first color you prefer (red at 255 for example)
3. Set the new fill layer to multiply
4. Ctrl Alt Shift E to create a new layer (name this red)
5. Deselect the Eye icon on your new Red layer.
6. Change the color of the fill layer to blue, then repeat step 4.
7. Repeat step 6 but now for green.

You now have 3 separated color layers, you can delete the fill layer at this point.

To recombine the layers:
Set the bottom layer blending mode to Normal, and the other 2 layers blending mode to Screen.
nice thanks! really!

Quote:
Originally Posted by MacBurg View Post
What you are doing above is based on luminosity values and has nothing to do with colour, well separating the colour info anyway, as you are disregarding the colour information in the first step.

There are various ways to view and work with just the colour info in an image though. You could convert the image to Lab mode and work on colour via the a & b channels which contain only the colour info in the image. You could create a saturation mask which shows you the colour info and strength within the image, here's an action that sets you up with a new channel that you can use as a mask -

http://www.mediafire.com/?udubkw7hb1w26sa

Check out the colour map in that action set too, it shows you the colour info in an image if you change the blending mode of the resulting layer back to "Normal". Also have a read of this thread over at MM -

http://www.modelmayhem.com/po.php?thread_id=774012

thanks

but i did not understand purpose of the action Q's Colour Map
about the last answer thanks a lot , i will print and translate and read carefully

Last edited by mantra; 08-08-2011 at 11:38 AM.
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  #12  
Old 08-09-2011, 03:03 AM
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Der_W Der_W is offline
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Re: how can i separate colors from light ?

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Originally Posted by Dropt View Post
Der_W,

I'm quite interested in where is that formula coming from, can you develop please ?

Also, I don't get why a 50% grey in luminosity is giving the colors as a result. The grey is standing for a 128 offset right ?

Edit : I think I get it; If you blend all your luminosity to a medium grey value, only remains the colors, and same goes for the colors. If all the colors are grey, only lights and shadow remains.
The formulas come from the YCbCr mode which uses the same formula for the Y (luma) as Photoshop uses for the luminosity blend mode: https://secure.wikimedia.org/wikiped...601_conversion
If you know how luma is calculated, chroma is easily extracted by subtracting the luma from the image. Since this again will sometimes result in RGB values that are < 0, you'll need to add an offset to the whole operation (+128, since this is the most unlikely to ruin the image in most parts).

Yes, the gray is the 128 offset and because when it's blended in "Color" mode, it has no color, so the chroma is vanished and just the luma stays in place.
In "Luminosity" mode on the other hand the luma is unified to 128 and the chroma can show through.
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  #13  
Old 08-09-2011, 08:53 AM
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mantra mantra is offline
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Question Re: how can i separate colors from light ?

hi
about the action http://www.retouchpro.com/forums/pho...tml#post295739

what could i do with the second action ?
the first create a mask
the second a gray layer , how could i mask the second action


cheers
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  #14  
Old 08-09-2011, 03:41 PM
Flashtones Flashtones is offline
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Re: how can i separate colors from light ?

I think what mantra wants is a saturation mask?

Check out this vid by Jonas/DerW:

https://www.youtube.com/watch?v=9xCo-nKpMSU

Or maybe this?

http://www.bensecret.com/2011/08/04/...-in-photoshop/

Not really sure. Mantra, you want the color separate from the luminosity to do what exactly?

Between Der W, MacBurg and others, I'm sure the knowledge is here to help you get what you are after, you just have to be clear what that is.
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  #15  
Old 08-09-2011, 04:28 PM
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0lBaldy 0lBaldy is offline
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Re: how can i separate colors from light ?

I might be wrong but I also think Luminosity Masks would be the solution...:

Tony Kuyper has a great explanation and tutorial on the use of Luminosity Masks (HERE) and Amica has provided an action (HERE) that puts all 12 Luminosity Masks (The 4 lights, 4 Darks, and 4 Midtones) into the Channels folder for your selection and use...
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  #16  
Old 08-09-2011, 09:32 PM
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John Wheeler John Wheeler is offline
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Re: how can i separate colors from light ?

Hello Mantra.

I will use Google Translate. I hope that helps with the communication. Please provide an image and a description of what you are trying to achieve. Do you want a "Layer Mask" as an end result? This would help us respond with better recommendations. Is your question already answered in one of the responses? Thanks.

Ciao Mantra.

Userò Google Translate. Spero che aiuta con la comunicazione. Si prega di fornire un'immagine e una descrizione di ciò che si sta cercando di ottenere. Volete una "maschera di livello" come risultato finale? Questo ci aiuterebbe a rispondere con una migliore raccomandazioni. È la tua domanda già risolta in una delle risposte? Grazie.
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  #17  
Old 08-10-2011, 01:06 AM
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mantra mantra is offline
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Re: how can i separate colors from light ?

Quote:
Originally Posted by Flashtones View Post
Mantra, you want the color separate from the luminosity to do what exactly?
.
thanks i got an action to create a saturation mask
yes i would like to separate color from the luminosity ,to tweak the colors in the photo without touching the lights
the blend color is good , but ... does change a little the lights ,according to the histogram

Quote:
Originally Posted by John Wheeler View Post
Hello Mantra.

I will use Google Translate. I hope that helps with the communication. Please provide an image and a description of what you are trying to achieve. Do you want a "Layer Mask" as an end result? This would help us respond with better recommendations. Is your question already answered in one of the responses? Thanks.
thanks for the translate
i will resize and upload a photos
yes i would like to have a layer mask (with only colors) to tweak them as well
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  #18  
Old 08-10-2011, 01:52 AM
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MacBurg MacBurg is offline
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Re: how can i separate colors from light ?

Quote:
Originally Posted by mantra View Post
hi
about the action http://www.retouchpro.com/forums/pho...tml#post295739

what could i do with the second action ?
the first create a mask
the second a gray layer , how could i mask the second action
Not sure I've been playing around with this colour layer for the last few days and haven't really came across anything worth writing about.

I find using the "Colour" blend mode really good for most adjustments targeted at colour, combined with a saturation mask you have a lot of control. If luminosity is changing when you change a colour then you need to look at the technique you're using to do this, maybe posting an image with example would be a great help here.

Another set of action you could try are the saturation masks by TheLightsRight studio, download them from here -

http://www.thelightsright.com/TLRSaturationMask
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  #19  
Old 08-10-2011, 07:43 AM
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Chain Chain is offline
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Re: how can i separate colors from light ?

Quote:
Originally Posted by mantra View Post
thanks i got an action to create a saturation mask
yes i would like to separate color from the luminosity ,to tweak the colors in the photo without touching the lights
the blend color is good , but ... does change a little the lights ,according to the histogram
There has been some confusion in this thread as to what you were trying to do. You do not want a mask at all.
  • Use the blend mode "Color" for adjustments that should only affect colors.
  • Use the blend mode "Luminosity" for adjustments that should only affect luminosity (percieved brightness).

Note: The histogram will not give you any useful information here, but any time you do adjustments it will change a little (because pixels are changing). This is regardless of blending mode.
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  #20  
Old 08-10-2011, 09:36 AM
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John Wheeler John Wheeler is offline
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Re: how can i separate colors from light ?

Quote:
Originally Posted by Chain View Post
There has been some confusion in this thread as to what you were trying to do. You do not want a mask at all.
  • Use the blend mode "Color" for adjustments that should only affect colors.
  • Use the blend mode "Luminosity" for adjustments that should only affect luminosity (percieved brightness).
I had to smile when you indicated there was a lot of confusion (I am still confused) yet you gave a firm answer implying you know exactly what Mantra wants. I hope that is the case because there is a lot of confusion to be cleared up. Mantra also indicated that an image would be posted so that should confirm what is desired.

On a related question to your statement about "Use the blend mode Color for adjustments that should only affect colors." That actually added to my confusion. My understanding of the Color blend mode was that it would preserve the luminosity of the source image below while replacing the color with color of the Blend Layer (with priority given to Hue and keeping Saturation best as the blend can but lower priority than either Hue of Blend Layer or Luminosity from Source below). This in my mind does not just isolate changes to just areas of color. Here is an example:

Source Layer is black to white gradient bottom to top (no color). Blend Layer is just solid yellow set to Blend of Color and masked to affect only right side of image (for comparison with original grayscale). All zero color portions of the gradient are changed, they just become less perceptible at low luminosity in the shadows and in the low saturation in the highlights. Clearly a lot of "no color" areas are being changed to yellow. I may be misunderstanding what you were saying in your post and am certainly interested. Here is the image:


Screen shot 2011-08-10 at 8.33.53 AM.png
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