Color/Luminosity separation

Started 3 months ago | Discussions thread
Tom Axford Veteran Member • Posts: 8,537
Re: Color/Luminosity separation

Pictus wrote:

Tom Axford wrote:

That can work fine provided you keep the colour and luminosity separate.

However, you have to eventually convert back to RGB to view your image. The problem is that by working on colour and luminosity separately you can easily go outside the RGB gamut (which is much less than colour + luminosity) and so the colours get distorted when you convert back to RGB.

Use a very large Color Space like ProPhoto RGB and there will be no problem.

Unfortunately, the problem is more fundamental than that and changing the colour space doesn't solve it.

It occurs because mathematically Lab colour has a much larger gamut than RGB.  However, the difference is not because some colours in Lab cannot be represented in RGB.  Instead, it is because Lab can represent saturated colours on a much wider brightness scale than is possible in RGB (whatever RGB colour space is used).

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