Color/Luminosity separation

Started 1 month ago | Discussions thread
Pictus
Pictus Veteran Member • Posts: 6,514
Re: Color/Luminosity separation

Tom Axford wrote:

We are talking about somewhat different things.

If you go increase the luminosity up to the maximum for all pixels, when you convert back to RGB (whatever colour space), the colours will often be washed out, possibly even to pure white. Exactly what happens on conversion from Lab to RGB will depend on the software, but usually the colour is not preserved if the luminosity is greater than RGB can represent for that colour.

Try it for yourself, I'd be interested to know what result you get. Create a pure white luminosity layer (i.e. maximum luminosity) and then combine your original colour layer with the white luminosity layer. When I have done that in GIMP, the result has not preserved the colours. There is no guarantee that Photoshop will do exactly the same.

In RGB color mode, a color layer above a white layer results in a 100% white image
In LAB color mode, a color layer above a white layer results in this

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