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  #1  
Old 11-07-2018, 08:00 PM
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ZeroID (Brent)
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RGB & Luminance

What do you do to add the Luminance channel to your RGB images. It's been puzzling me for a while. My efforts have always overloaded the channel I've added it to and unbalanced the colours in the image.

Forgive me if you guys already know this process but I've discovered L*a*b colour. Anyone familiar with it's use ? I watched a video that showed how to switch to Lab colour mode then add L as another layer, adjust it's luminosity % in properties then flatten the image and revert back to RGB. It essentially just boosts all the colour saturations equally so no colour balance problems. Looks like I might be going back to some earlier images and having another go at them. Might as well, weather has not been very helpful lately
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  #2  
Old 11-07-2018, 08:18 PM
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codemonkey (Lee)
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The method used to combine them will largely depend on the software that you have. Sounds like you're using Photoshop there, which I've never used for that purpose (or maybe I did in the very beginning...?)

I use PixInsight, in which you typically use LRGB Combination to combine your L and RGB data (after first stretching it).
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  #3  
Old 12-07-2018, 02:43 PM
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Andy01 (Andy)
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Lab mode is useful for boosting star colours.
Just adjust the b curve evenly for a nice boost in blue/yellow,
Then convert back to RGB.
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  #4  
Old 12-07-2018, 02:56 PM
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RickS (Rick)
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CIELAB is a useful colour space if you want to work on lightness and colour independently. As Andy suggested, you can use it for tweaking colours with the advantage that this doesn't affect lightness. You can also manipulate the Lightness (noise reduction, sharpening, etc.) independently of colour.

Cheers,
Rick.
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  #5  
Old 12-07-2018, 07:07 PM
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multiweb (Marc)
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Quote:
Originally Posted by Andy01 View Post
Lab mode is useful for boosting star colours.
Just adjust the b curve evenly for a nice boost in blue/yellow,
Then convert back to RGB.
That's a neat trick and it dials down the greens too.
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  #6  
Old 12-07-2018, 07:21 PM
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ZeroID (Brent)
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Excellent ! Thanks all, can always learn something new here.
> Lee, yes Photoshop.
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